Challenges For Regional Development Under The Impact of Global Climate Change

Challenges for Regional Development under
the Impact of Global Climate Change
The Yesa Reservoir in the Spanish Pyrenees as an example
Author: Axel Winterscheid
Contact:
Darmstadt University of Technology / Institute of Hydraulics and Water Resources Engineering
Email: winterscheid@ihwb.tu-darmstadt.de
Internet: http://www.tu-darmstadt.de/fb/bi/wb/ihwbhome.htm
Prepared in May / June 2002 at the Dept. de Erosion y Usos del Suelo, Instituto Pirenaico de
Ecología, CSIC / Zaragoza
I N CO OP E R A T IO N W I T H AND
Institute of Hydraulics
and W ater Ressources
Management
I want to thank J. M. García Ruiz and López-Moreno J. I. for the

extensive and good support and the possibility to prepare this report at
the Instituto Pirenaico de Ecología / Zaragoza. Furthermore I want to
thank Prof. Dr.-Ing M. Ostrowski (TU Darmstadt / Institute for
Hydraulics and Water Resources Engineering) and Dipl-Ing. E. Petersson
(TU Darmstadt / Center for Interdisciplinary Studies of Technology) for
the very good assistance before, while and after my time at the Instituto
Pirenaico de Ecología / Zaragoza
Axel Winterscheid
C H A L L E N G E S F O R R E G I O N A L D E V E L OP M E N T U N D E R T H E I M P A C T O F G L O B A L C L I M A T E C H A N G E
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Complex 1 : Climate Prognosis .........................................................................................................2
1.1 THE CLIMATE SYSTEM .......................................................................................................... 2
1.1.1 Large scale oscillation systems ..................................................................................... 3
1.1.2 Global climate change .................................................................................................. 3
1.1.3 Effects of climate change............................................................................................... 4
1.2 CLIMATE MODELS................................................................................................................. 7
1.2.1 Downscaling.................................................................................................................. 8
1.2.2 Emission scenarios........................................................................................................ 8
1.3 CLIMATE PROGNOSIS IN THE SPANISH PYRENEES .............................................................. 10
1.3.1 Temperature ................................................................................................................ 10
1.3.2 Precipitation................................................................................................................ 11
1.3.3 Run-off......................................................................................................................... 11
1.3.4 Annex........................................................................................................................... 13
Complex 2 : The Yesa System .........................................................................................................17
2.1 ORIENTATION ..................................................................................................................... 17
2.1.1 Topography and geology............................................................................................. 17
2.1.2 Climate ........................................................................................................................ 18
2.1.3 Hydrology and flow regimen....................................................................................... 18
2.1.4 Vegetation ................................................................................................................... 19
2.1.5 Population and economy............................................................................................. 20
2.2 ACTUAL YESA RESERVOIR ................................................................................................. 20
2.2.1 The operation of the Yesa reservoir from 1959 to 2000.............................................. 21
2.2.2 Data quality................................................................................................................. 22
2.3 YESA ENLARGEMENT PROJECT ........................................................................................... 23
2.3.1 Spanish water policy ................................................................................................... 23
2.3.2 History of the project................................................................................................... 24
2.3.3 Valuation of the project............................................................................................... 25
2.4 MODEL OF THE YESA RESERVOIR....................................................................................... 27
2.4.1 Run-off scenarios......................................................................................................... 28
2.4.2 Modeling of the actual reservoir ................................................................................. 29
2.4.3 Hypothetical enlarged Yesa reservoir from 1959 to 1995 .......................................... 31
2.4.4 Future Yesa reservoirs ................................................................................................ 32
2.4.5 Conclusions ................................................................................................................. 33
2.5 CHANGING OF THE YESA SYSTEM ...................................................................................... 33
2.5.1 Socio-economical system............................................................................................. 34
2.5.2 Ecological system........................................................................................................ 35
Complex 3 : Strategies against Climate Change ....................................................................37
3.1 HISTORY OF INTERNATIONAL CLIMATE PROTECTION ........................................................ 37
3.2 GLOBAL STRATEGIES AGAINST CLIMATE CHANGE AND ITS EFFECTS ................................. 38
3.2.1 Prospects ..................................................................................................................... 38
3.3 LOCAL STRATEGIES AGAINST CLIMATE EFFECTS ............................................................... 39
3.3.1 Areas of conflicts......................................................................................................... 39
3.3.2 Supply-Management based solution............................................................................ 40
3.3.3 Demand-Management based solution ......................................................................... 41
Summary........................................................................................................................................................43
Conclusions .................................................................................................................................................44
References ....................................................................................................................................................45
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COMPLEX 1 : CLIMATE PROGNOSIS
1.1 THE CLIMATE SYSTEM

Climate is defined as the average condition over a sufficiently long period of time of the
atmosphere at a fixed place on the Earth’s surface (Meyers Lexikon 1992). A climatic condition is
composed of air-pressure, radiation, temperature, precipitation, air humidity, wind, lightning, etc..
The main driver for the climate system is the solar energy received as short-wave radiation on the
Earth’s surface. The climate system can be subdivided into the following sub-systems:
Atmosphere is defined as the mantle of air surrounding the Earth.
Hydrosphere is defined as the mantle of water covering the Earth (oceans, groundwater,
inland water, water existing in the atmosphere).
Cryosphere is composed of inland ice, glaciers, snow fields and permafrost.
Lithosphere is defined as the Earth’s crust and upper mantle of rocks.
The topmost layer of the soil is called the Pedosphere.
Biosphere is the totality of the terrestrial living space of plants and animals.
Figure 1: The Natural Earth system
Looking at the climate system over a long period of time there is an equilibrium of energy between
incoming and outgoing energy. But different time-scales of the ongoing processes within and
between the various climatic sub-systems are disturbing this equilibrium. The processes passing
within the atmospheric sub-system have the shortest time-scale ranging from months to several
years. Therefore the atmosphere is called the fastest climatic sub-system (M. Clausen 2001). Processes
however occurring in the deep layers of the oceans range at a time-scale between 100 and 1000
years. The lithosphere has the longest time-scale with up to 108 years for the drifting of the
continents.
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1.1.1 LARGE SCALE OSCILLATION SYSTEMS
Looking for systematic structures within the global climate system several regional climate system
were discovered. In the sixties of the 20. century a connection was established by Jacob Bjerknes
between one of these regional climate systems, i.e. the Southern Oscillation, and the periodical
appearance of the El Niño phenomenon. He detected not only a warming of surface water at the
west coast of South America causing the El Niño phenomenon but also a temporary corresponding
warming of surface water some thousand kilometres away in the middle of the Pacific Ocean. The
El Niño and the contrasting La Niña phenomenon, causing an extreme cooling of the surface water
at the west-coast of South America, are the result of dynamic interactions between ocean and
atmosphere attempting to establish an equilibrium condition. After 20 years of investigation on the
El Niño phenomenon one begun to identify more of these large-scale oscillations. Till today several
oscillations were discovered, namely the North-Atlantic, Arctic, Antarctic and the Pacific Oscillation
(Lippsett 2002).
Figure 2: Surface temperatre changes between 20°N Figure 3: El Niño phenomenon

and 90° N associated with the North Atlantic
Oscillation (NAO); the Southern Oscillation; and
combined – (NAO + SO)
The North-Atlantic Oscillation (NOA) is the “weather making machine” for Europe, in charge of
large-scale high and low pressure areas. The NAO index describes the difference in pressure
between the low pressure area over Iceland and the high pressure area over the Azores. A positive
NOA index stands for high difference in pressure; a negative NAO index stands for a low
difference in pressure. This index can be seen in figure 2 varying from positive to negative values or
reverse within some weeks or months. The reasons for the fluctuation of the NAO still remains
unknown, but according to latest scientific research “water islands of different temperature” in the
North-Atlantic are presumably responsible (L. Lippsett 2002). Since 1980 the NAO index remained
positive, except in 1995, accompanied by additional rainfalls in the Scandinavian region, droughts on
the Iberian Peninsula and heavy storms in Northern Europe.
1.1.2 GLOBAL CLIMATE CHANGE
The climate is the result of the complex ensemble of processes within or interacting between the
various sub-systems and boundary conditions, all contributing to a condition of equilibrium. Each
alteration influencing this condition of equilibrium has climatic effects, therefore might change the
climatic parameters (F. Zimmerl 2001).
Changes within the climate system have been observed. Burning fossil fuels, land-use changes and
the agricultural sector have changed the concentration of greenhouse gases and aerosols in the
atmosphere (IPCC 1995). These rapid disturbances of the radiation balance, relative to a reference
condition before the occurrence of the disturbance, is called a driver of climate (U. Schurath et al.
2002). This driver of climate causes a warming of the Earth’s surface in case of the higher
concentrations of greenhouse gases in the atmosphere. The IPCC already emphasised in 1995 the
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cooling effects of anthropogenic aerosols in the atmosphere, but the capability to lower the warming
process still remains unknown.
The IPCC reported observations made about systematic trends in climatic conditions. The global
mean temperature has increased about 0,3 to 0,6 °C since the end of the 19th century. In correlation
with increased mean temperatures satellite measurements detected a decrease of snow-covered areas
of about 10 % since the end of the sixties (F. Zimmerl 2001). Higher precipitation patterns in high
northern latitudes and lower precipitation patterns over subtropical latitudes (10°N to 30°N) were
observed. Some African or Asian regions experienced several periods of droughts in the last decades
with an increase in frequency and intensity. Particularly the extreme events of temperature and
precipitation caused by the El Niño phenomenon since the seventies were clearly capers of weather
to be observed by everyone. In 1982 the strongest El Niño period of the last century took place
with droughts in Australia, flooding in Peru and Ecuador and heavy storms in California claiming
thousands of casualties and causing damages of around 13 billion dollars.
On the other hand the climate system was always subject to changes of non-anthropogenic
background. The main task of research will be to separate natural fluctuation of the oscillation
systems and external effects (fluctuation of solar radiation and volcanic activities) more precisely
from anthropogenic influences on the climate system. Despite the fact that no ultimate natural
scientific analysis and explanation is available, serious science does not dispute the existing climate
change due to anthropogenic activities anymore.
1.1.3 EFFECTS OF CLIMATE CHANGE
M. Claussen (2001) defines the complete Earth’s system to be composed of the climate system (or
natural Earth system) and the anthroposphere. Humans may be considered as part of the biosphere
but many aspects of human actions like the psychic and cultural components cannot be described
quantitatively. It is possible to sketch future scenarios of physical effects of climate quantities like
wind, temperature and precipitation by applying climate models. But to design future scenarios of
the anthroposphere more non-deterministic quantities (human decisions) must be considered. These
future scenarios of climate quantities constitute the data base for making decisions in order to
weaken or to prevent the expected physical effects on the anthrosphere. But already now the
vulnerability of human society and natural systems to climate extremes is demonstrated by the
damage, hardship, and fatalities caused by events such as droughts, floods, heat waves and
windstorms.
1.1.3.1 SOCIAL AND ECONOMIC SYSTEM
The climate change will have devastating effects on the socio-economic sector. The rising of the
sea-level will threaten coastal areas and islands. Cities like New York, Boston or Tokyo are just some
examples for possible victims of the flooding. In third world countries like Bangladesh extensive
migration movements are expected due to loss of residential areas and farmland. More frequent and
longer drought periods will increase the extraction of water from groundwater reservoirs. The
groundwater table will drop with the effect of salinity of groundwater reservoirs situated in coastal
areas. In addition lower precipitation in some regions will endanger the water supply of about 3
billion people worldwide according to information of the Worldwatch Institute (1999). Inevitably
this will cause social tension within societies as well as it will increase the political tension between
neighbouring nations of water resources (groundwater reservoirs, rivers, lakes). Furthermore lower
run-off in rivers will affect the efficiency of water-power plants. Higher risks of flood events will
increase the damage on infrastructure subsequently increasing the premium for insurances. M.L
Parry (2000) states that especially the insurance sector is sensitive to changing patterns of extreme
events, particularly through their impact on property damage.
Also on the human health climate change will have direct and indirect effects. Heat waves strain the
human circulation and a general warming and shifting of the climate zones facilitate the spreading of
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infectious diseases like Malaria or Cholera.

Occasional positive effects can be observed. For example higher temperatures will have a positive
effect on the agriculture sector increasing the periods of cultivation in some regions or lowering the
costs for heating. But all these positive effects are not valid on a global scale.
The Hans Seidel Stiftung (2000) states that the climate change is first of all a problem of the none-
western world with high dependency on the agricultural sector. The industrial world might be able
to provide sufficient financial resources to moderate the negative effects of the climate change. But
in a long-term view environmental catastrophes and the possible socio-economical destabilization in
chiefly affected countries will endanger their economical development and their important trade
relations with the industrialized countries. In the worst case a destabilized situation might expand
into international conflict of worldwide significance.
1.1.3.2 ECOSYSTEMS
The ecosystem is defined as the local biological community and its pattern of interaction with its
environment. The ecosystem is directly affected by climate change in terms of a higher CO2
concentration, temperature and precipitation as well as indirectly by human impacts caused by the
effects of climate change.
Ecosystems have a high diversity due to a complex regional climatic pattern and it is known for sure
that two different local ecosystems will react differently to the effects of climate change. Generally,
warming and CO2 enrichment are likely to increase productivity in most ecosystems assuming no
significant changes in temperature and precipitation. A change of precipitation as well as a
temporary shifting may have negative consequences for the productivity due to water shortage in
the growing season. Furthermore a change in the temperature pattern will shift the spatial limits of
ecosystems. Particularly endangered are sensitive high specialised ecosystems like the high-alpine
vegetation. GLORIA (Global Observation Research Initiative In Alpine Environments)1 is a pilot
scheme to investigate the changes within alpine environment. Therefore a European wide
observation network has been assembled from the Spanish Sierra Nevada to the polar Ural in order
to collect data material.
According to the Manning M. et al. (2001) the marine ecosystems are very sensitive to climate
change. Large scale impacts of climate change on oceans are expected to include increases in sea
surface temperature and changes in salinity, which will strongly affect fish abundance and
population dynamics. Rising sea levels will affect costal ecosystems like coral reefs, atolls and
mangroves
But there are more indirect climate effects changing environmental conditions for ecosystems.
Higher temperature accelerates the generation of pest, which threatens the forestall ecosystem. Also
a changing of the hydrosphere, lithosphere and cryosphere will have an effect on the further
development of the ecosystem.
As a rough summary change in the composition of species is expected within the ecosystem. More
adaptable species will displace more inflexible ones. Furthermore it is expected that very sensitive
ecosystems with a low capability of adjustment will disappear, e.g. corals, polar and alpine
ecosystems.
1.1.3.3 SOIL AND LAND RESOURCES
The lithosphere is impacted directly and, through land use change, indirectly on a wide range of
soil processes and properties that will determine the future ability of land to fulfil the key functions
that are important for all terrestrial ecosystems and the agricultural sector (M.L. Parry 2000). Already
1 More information available under (http://www.gloria.ac.at)
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in the last decades human activities were causing a large scale physical degradation of soils
worldwide. These land degradations processes are salinization, peat wastage, acidification, erosion /
desertification and soil compaction and are seen to increase in the future under more arid
conditions.
As a result of the degradation of high-mountain permafrost and shifts in precipitation patterns slope
stability will decrease and enhance rockfalls and mudslides will occur more frequently. The
magnitude of any change however will vary between geographical locations and will depend on
precipitation distribution and intensity. There is uncertainty in the possible effects of climate change
on the future nutrient state and the response of soil organisms, which is affecting the future
development of the vegetation. The lithosphere is integrated into the climate system and therefore
every change may have at least indirect effect on the future development of the global climate.
Furthermore the future development of the soil is of great importance for the agricultural sector.
Climate change will perturb the geographic distribution of agricultural land use.
1.1.3.4 WATER RESOURCES AND RESERVOIRS
The changes in future availability of water resources with sufficient quality depends on climate
change as well as the future water demand, the latter dependent on population growth and
economic development. Today the agricultural sector is using about 70 % of the total consumption
and according to estimations the total water consumption will be six times higher in 2025 than it
was in 1900 (Hauchler I. 2000). The growing world population intensifies the agricultural sector, soil
degradation increases the pressure to cultivate farmland of poor quality in arid zones and higher
temperature increases the evapotranspiration. Altogether the pressure on the water resource will
become stronger, especially in third world countries located in arid and semi-arid regions (Hauchler
I. 2000).
Higher temperatures have a strong effect on the hydrological cycle, particularly the Cryosphere is
affected. Where snowfall has currently great importance on the flow regime a more intensive peak
streamflow may occur, which in addition would move from spring to winter. A change in the flow
regime of river will have implications for erosion and sedimentation. Flood magnitude and
frequency could increase as a consequence of heavy precipitation events and land use changes.
Lower run-off and higher water temperatures especially during summer months impairs the water
quality and affects the aquatic ecosystem, particularly were quality is already under threat. Higher
evapo-transpiration reduces the regeneration of groundwater resources and the soil moisture.
Water resource management techniques must adapt themselves to the changing hydrological
situation. Large reservoirs were constructed to provide sufficient water resources during periods of
water scarcity, to generate hydro electrical power or to control floods. M.L Parry (2000) states that
adaptation to climate change will involve a combination of supply-side (altering the water) and
demand-side (altering the demand for the resource or exposure to hazard) actions.
Reservoir systems are sensitive with regard to changing climate impacts. Higher flood events
generated by heavy rainfalls or in combination with rapid snowmelt threaten the dam safety.
Methods to design the spillways vary from country to country but in general they are designed to
carry flows with a return period of 1000 years to the Probable Maximum Flood (PMF) (WCD
report). The PMF is based on the Probable Maximum Precipitation (PMP), which can be defined as
“theoretically the greatest depth of precipitation for a given duration that is physically possible over
a given size storm area at a particular geographical location at a certain time of year” (World
Meteorological Organisation 1986). Just one single study into potential effects of climate change on
the very extreme floods used in dam safety assessment has been published. The general statement
was that increasing magnitudes of extreme precipitation events due to global warming would, of
course, lead to an increase in the magnitudes of extreme floods (N. Arnell et al. 2000).
Climate change has a great impact on the performance of a reservoir. The ability to meet its design
objectives is a function of the inflow, reservoir evaporation and the water demand; all three are
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subjected directly or indirectly to impacts of climate change. “Other things being equal, the larger
the reservoir storage relative to both inflows and releases, the less sensitive the reliability of the
reservoir is to changes in inputs” (N. Arnell et al. 2000). Furthermore the higher stress on the
available water resources might endanger the guarantee to admit an outflow higher than the
ecological flow to the natural river.
Increased soil erosion as an effect of climate change increases the amount of sediments available to
rivers. In conjunction with higher flows equivalent to higher sediment transport rates this would
aggravate the sedimentation in many reservoirs. Also with regard to this aspect no studies into the
implications of climate change for reservoir sedimentation has been published, largely because there
have been few investigations into potential changes in soil erosion (N. Arnell et al. 2000).
The reservoir water quality depends on the quality as well as quantity of the inflows. The further
development of water quality stored in reservoirs largely depend on the temperature profile of the
water (G. Bergkamp et al. 2000) In temperate climates lakes and reservoirs are subjected to seasonal
cycles of the thermal stratification. These annual mixing events have a positive effect on water
quality in deep layers. Water in deep layers, called hypolimnion water, are of poor quality with little
or no dissolved oxygen. Reservoirs in hot climates however are not subjected to this physical
structure. Therefore releasing hypolimnion water could adversely affect the ecosystem of
downstream areas.
It could be seen in the previous discussion that the future performance of reservoirs depends on
impacts of climate change as well as it has to be seen “in the context of other changes affecting
reservoir reliability, such as changes in water demands, efficiency of use and operating, and
organisational characteristics. Land use changes can also affect the resource base”. (G. Bergkamp et
al. 2000).
1.2 CLIMATE MODELS

“Global Climate Models (GCMs) are mathematical representations of atmosphere, ocean, ice and
land surface processes based on the known laws of physics describing the motion of energy and
moisture” (M.L. Parry 2000). These models are discrete solving the equations in a 30 min (typically)
interval on a grid typically between 250 km and 600 km. This rough resolution creates problems.
Most of the climatic phenomena are of smaller scale than the grid resolution, for example clouds
with an extension usually smaller than some hundreds of kilometres reflect a great part of the
incident solar radiation back to the space and are of great significance for the temperature. GCMs
represent these small scale effects not as individual phenomena but as a collective. This method is
called “parameterisation” (M. Clausen 2001).
In order to simulate the entire mode of action of the climate system all interlinked sub-systems as
well as the influence of feedback effects have to be taken into consideration. An effect of higher
temperature, for example, is that sea-ice starts melting. This will reduce the amount of sunlight
reflected and thus enhance the warming in high latitudes – a positive feedback. “The greatest
uncertainties in model prediction come from these feedbacks and in particular possible changes in
the behaviour and characteristics of clouds in a warmer world; we do not even know if these
feedback will be positive or negative” (M.L. Parry 2000). Climate sensitivity can be seen as a
measure of uncertainties in the way of simulation of these feedbacks or better “sensitivity is the
degree to which a system is affected, either adversely or beneficially, by climate related stimuli”
(IPCC 2001). In actual climate modelling this sensitivity spans a range of temperature in °C
approximately between 1.5°C and 4.5°C.
Reducing the temporal horizon of the prediction leads to more exact results because a lot of slow
reacting sub-systems of the climate system can be neglected. Implementing a climate model for
short-term weather forecasting the long-term reacting vegetation-system or a changing of the
chemical composition of the atmosphere (e.g. CO2 concentration) can be neglected. Increasing the
temporal horizon of the climate prediction, higher uncertainties due to long-term reacting climatic
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sub-systems can be observed in the obtained results. “The climate changing of today results from
sins done 30 or 40 years ago” (M. Latif 2002).
Current climate models are still based on numerical input of projected future emission rates. Future
climate modelling, however, with the development of the vegetation and the socio-economical
system will obtain feedbacks therefrom. The vegetation has a strong effect on future climate as a
sink or a well for CO2. The future development of economy and world population will have a strong
effect on the output of greenhouse gases.
1.2.1 DOWNSCALING
The climate change scenario information for Europe presented by the (M.L. Parry 2000) shown
in chapter 1.2.2 was depicted at the spatial scale of GCMs. GCMs are regarded to be reliable for
modelling global or continental scales. Due to the low spatial resolution with grid widths between
250 km and 600 km the results cannot directly applied to achieve information on a regional scale,
because within a single grid box there may in reality be different climate responses to anthropogenic
forcing. Modern computers are still not providing sufficient power to run GCMs on grids of a
regional scale. The way out of this dilemma is the Downscaling technique. There are three options for
downscaling:
Single interpolation: One of the crudest ways of adding spatial detail to GCM-based climate
change scenarios is to interpolate GCM-scale changes to a finer resolution and then
combine these interpolated changes with observed climate information at the fine
resolution. (M.L. Parry 2000)
Regional climate models (RCM): Here a regionally limited climate model driven by a
boundary condition from GCMs is used to generate a finer resolution, e.g. 30 km to 50 km
grid to cover an area of the size of Europe. These RCMs are totally dependent on the
boundary condition given by the GCM. Therefore the RCM scenarios greatly depend on
the validity of its driving GCM. The disadvantage of RCM is the high and expensive
computational effort.
Statistical downscaling: Applying regression methods, circulation typing schemes and

stochastic weather generators, climate scenarios obtained by GCMs, can be downscaled to a
regional grid. Necessary input for Statistical Downscaling are extensive observational data at
several sites covering the region of interest – daily/hourly weather data for the surface and
the air
1.2.2 EMISSION SCENARIOS
Figure 4: The four SRES scenarios of the IPCC

The purpose of scenarios is not to predict the future based on a set of quantified probabilities,
but to set out a broad range of possibilities in order to provoke societal discussion and debate (M.L.
Parry 2000). Scenarios were developed by the IPCC Special Report on Emissions Scenarios (SRES)
relying upon two orthogonal axis, representing social values (ranging from Consumerist to
Conservationist) and level of governance (ranging from local to global). The four quadrants are
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indicating four different storylines, i.e. each a combination of a political and economical state with a
social value. The characteristics of these four scenario families are described by IPPC (2001) as follows:
A1 / World Market: An increasingly globalised world with short-term and materialistic-
consumerist social values. The gap between rich and poor will grow, leading to rising crime
and social tension. States will lose external power but then multinational firms steadily
achieve greater power. The ecological system experiences a trend towards general
deterioration. Emission trading will be part of the global strategy to stop the climate change.
A2 / Provincial Enterprise: This world takes its policy decision on a national or even on a
sub-national level. Characteristics of this world is a protectionist economy and trade policy,
that will cause more global inequality between the first world and the developing countries.
Environmental quality has a much lower priority than protecting national economy and
meeting short-term consumer demands. Therefore no international climate convention
might be expected and the ecological system suffers the greatest deterioration of all four
scenarios.
B1 / Global Sustainability: Here a high level of environmental and social consciousness

combined with a globally coherent approach facilitates a more sustainable development. In
contrast to the A1 scenario the B1 scenario invests a large part of its gains into improved
efficiency of resource use, social equality and environmental protection. This implies an
improvement of the condition of the ecological system. The globalised economic system is
strong and the international community will agree on strong climate regime to protect the
world climate.
B2 / Local Stewardship: Environmental problems will be solved by applying longer-term

based solutions, which are seen to be more attuned to local needs and circumstances. The
world is more heterogeneous because governance is seen to shift down to the national and
local level in accordance with the principle of subsidiary. The environmental system
benefits under this scenario, but not as much as under the B1 scenario because of the
limited extend of spatial co-ordination.
CO2 Global.mean
ACACIA Climate Global-mean sea
Concentration temperature
Scenario sensitivity [°C] level [cm]
[ppmv] increase [°C]
B1-low 1.5 491 0.97 13
B2-mid 2.5 502 1.58 37
A1-mid 2.5 547 1.63 38
A2-high 4.5 572 2.64 68
Table 1: The four ACACIA (2000) scenarios and their estimates of changes for the 2050s (i.e. 2055)
Each of the above described scenario families must be considered as an “umbrella organisation”
uniting fine-tuned individual scenarios. The scenario families is a description of the future condition
of the Earth. First the individual scenarios are of quantitative character, utilizable as a numeric input
for models.
To relate the above described scenarios to climate change the climate-relevant outcome in terms of
greenhouse gas emissions was determined for each of the four scenarios. Table 1 shows the
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greenhouse gas emissions used in the ACACIA project to predict the European climate change. On
account of the higher environmental consciousness the emissions of greenhouse under the B1 low /
Global Sustainable scenario, for example, is much lower than under the A1 mid / World Market
scenario.
1.3 CLIMATE PROGNOSIS IN THE SPANISH PYRENEES

The Pyrenees are ranging from the Gulf of Biscaya / Atlantic Ocean to the Mediterranean Sea. This
mountain range with peaks up to 3400 m height forms a natural as well as a political boarder
between Spain and France. The large-scale grids of GCMs are not able to represent the pattern of
local climate, topographic or hydrological characteristic of the Pyrenees. Therefore the climate
scenarios obtained from GCMs hold a high level of inaccuracies.
1.3.1 TEMPERATURE
J. M. García Ruiz et. al. (2001) carried out a trend analysis of temperature using the data of
meteorological stations all located within the Spanish Central Pyrenees. The period of time which
was analysed is ranging from 1940 to 1999.
According to J. M. García Ruiz et al. (2001) the history of temperature can be subdivided into three
phases. From 1942 to 1948 with higher temperatures than normal, between 1959 to 1978 a cooler
phase and as of 1970 till 1990 a period with constantly increasing temperatures. Figure 5 shows a
high variability with strong temporary trends, positive as well as negative, but no long-term trend in
temperature in the Spanish Central Pyrenees can be detected.
Figure 5: Regional index of mean annual temperature of meteorological station located in the Aragon’s Pyrenees
In contrast to the observations made all ACACIA climate scenarios (refer to figures 9 and 10)
predict an increase in the mean temperature and the probability of hot summers and warm winters
for the grid box including the mountain range of the Pyrenees, no statements about the
development of single temperature extremes were published. Comparing the ACACIA climate
scenarios with the observed data base attention must always be paid to the fact that the climate
scenarios are calculated by GCMs using a resolution of some hundreds of kilometres. Regional
climatic effects have a great impact on the local climate in the Pyrenees and the study area for the
temperature analysis is much smaller than one grid box in the GCM. On the other hand the regional
observation cannot be used to invalidate the ACACIA climate scenarios. For that, the statistical
analysis carried out is too weak and regionally focused. Again the variability of regional climate
effects and long-term climate variability could have hidden a existing trend in temperature.
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1.3.2 PRECIPITATION
J. M. Garcia Ruiz et. al. (2000) carried out a trend analysis of precipitation (1919 – 1999) using the
data of meteorological stations all located within the Spanish Central Pyrenees. Like for temperature
no long-term trend can be observed but a high variability with strong short-term trends. Again the
history of precipitation can be subdivided into several phases of dry and wet years. Since 1960 a
decrease in precipitation can be observed but as of 1990 a strong positive trend lifts the index into a
positive zone. Over the last decades a higher variability in the succession of dry and wet years can be
recognized from the analysis.
The B1-low ACACIA climate scenario predicts for the Pyrenees no significant changes in the
precipitation pattern during the winter months and a 16 % reduced mean precipitation in summer.
The A2-high scenario for precipitation, which might cause the most serious changes in the climate
system, shows during winter (figure 12) for the north-western Pyrenees a slight decrease in
precipitation; in the south-eastern Pyrenees, however, an increase. During the summer months
(figure 11) a drastic decrease in precipitation must be expected. Comparing the results of both tudies
attention must be paid again on the regional character of the statistical analysis carried out by J. M.
Garcia Ruiz et al. (2000) and the low spatial resolution of ACACIA climate scenarios.
Figure 6: Regional index of mean precipitation of meteorological station located in the Aragon’s Pyrenees
1.3.3 RUN-OFF
J.Garcia Ruiz et. al. carried out a trend analysis of run-off (1919 – 1999) using the data of gauging
stations all located at different rivers within the Spanish Central Pyrenees. The index shows since
1961 a decreasing trend in run-off. This trend can just be explained by a continuous changing of the
covering vegetation as no climatic changes have been identified as underlying cause. S. Begueria et
al. confirmed this in a study about the catchments of various rivers in the Central Spanish Pyrenees.
They stated that “the regional climatic indices (Figures 5 and 6) confirmed a climatic cycle of 15 –
20 years”, but they did not find any “evidence of a clear annual climatic trend since the middle of
the 20th century. They found the reason for the negative trend in discharge to be major changes in
land management. “Since the middle of the 20th century most cultivated fields in the hillslopes (22 %
of the study area) were abandoned and progressively covered by dense shrub and forests. At the
same time, man-induced fires have been reduced drastically.”
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Figure 7: Regional index of mean annual run-off at several gauging station at different rivers all located in the
Aragon’s Pyrenees
The ACACIA Project (M.L. Parry 2000) published for each future world scenario a corresponding
run-off scenario. All these run-off scenarios show a negative trend for the Central Spanish Pyrenees
of about 10 % – 25 % relative to the 1961 – 1990 mean due to lower precipitation and higher
evapo-transpiration; possible changes in land use and vegetation have not been considered. The
climatic input for the hydrological model came from GCMs. The WCD report concludes that
translating a given climate time series into a hydrological response in general adds relatively little
additional uncertainty (WCD 2000).
Figure 8: Change in average runoff across Europe 2050s relative to the 1961 – 1990mean
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1.3.4 ANNEX
Figure 9: (left panel) Change in mean winter (DJF) temperature for the 2020s, 2050s and 2080s with respect to
1961 – 1990 for the A2-high scenario; median of eight GCM simulations. (right panel) Inter-model range in mean
winter temperature change.
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Figure 10: (left panel) Change in mean summer (JJA) temperature for the 2020s, 2050s and 2080s with respect to
summer temperature change.
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Figure 11: (left panel) Change in mean winter (DJF) precipitation for the 2020s, 2050s and 2080s with respect to
winter precipitation change.
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Figure 12: (left panel) Change in mean summer (JJA) precipitation for the 2020s, 2050s and 2080s with respect to
summer precipitation change.
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COMPLEX 2 : THE YESA SYSTEM
2.1 ORIENTATION
The Yesa reservoir is located in the Central Spanish Pyrenees close to the French boarder. The
study area belongs to the Spanish Region of Aragon with the capital Zaragoza. In the west the dam
of the Yesa reservoir is situated on the boarder to the adjacent Region of Navarra. The size of the
Yesa catchment area is about 2181 km² and the water surface of the reservoir at maximum filling
level amounts to 2098 ha.
2.1.1 TOPOGRAPHY AND GEOLOGY
The topography of the catchment area includes various zones. The northern landscape shows the
form of a high-alpine relief. The more southern landscape shows extensive areas with hilly or a
plane relief. The relief of the catchment area can be divided into five zones with an east – west
orientation, which are coincident with the different geological units.
Figure 13: Topography Figure 14: Geological units
The characteristics of the zones are, starting from the north, as follows
Pirineo Axial: Formed out of granitic material from the Palaeozoic. Due to the great
lithotomic variability the area must be considered as very homogeneous. The topography
can be described as partly smooth and partly very steep and rugged. The highest peak is the
Anayet with a height of 2559 m.
Sierras Interiores: Formed out of Mesozoic limestone and sandstone. The relief is very
irregular with very high vertical rocks and karstified areas. Here are the highest peaks of the
Yesa – catchment with up to 2886 m (peak Collarada).
Flysch Sector: South of the Sierras Interiores follows a sector, consisting of Eocene flysch.
The relief is smooth and homogeneous with elevations up to 2000 m. Contact with the
marls of the Inner Depression is at about 800m, by means of an overthrusting fault.
La Depresion Interior: The Inner Depression can be described as a large corridor forming
a large valley from the west to the east with varying altitudes between 600 m and 850 m. It
is composed of Eocene marls. Most of the landscape is occupied by fluvial terraces and
short pediments (glacis).
El area meriodional: This zone is composed of conglomerates and clay with a hilly relief.
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Management
2.1.2 CLIMATE
Temperature shows a clear upward trend from the north to the south. Precipitation increases
towards the north along the altitudinal gradient. The regional climate can clearly be subdivided into
two zones. The northern and western zone is influenced by Atlantic climate with precipitation of
more than 1500 mm / year, the southern and eastern zone including the Inner Depression is
influenced by Mediterranean climate with lower precipitation of e.g. 720 mm / year in Artieda. A
0°C isotherm has been detected in an altitude of about 1549 m for the catchment area of the Rio
Aragon (J. M. García Ruiz et al. 2001).
Downstream the Yesa reservoir the Rio Aragon reaches a large plane area with arid climate
conditions. According to J. Herrero et al. (1996) the Ebro Valley is the most arid inland valley with a
the mean annual precipitation of 337 mm in contrast to a mean evapo-transpiration of 1069 mm.
2.1.3 HYDROLOGY AND FLOW REGIMEN
A good network of gauging stations covers this catchment. The available time series are up to 90
years long with a daily resolution. Figure 15 indicates the locations of the network.
Figure 15: Network of gauging station in the Yesa system
J. M. García Ruiz et al. (2001) have characterised the discharge behaviour of the Rio Esca as a clearly
oceanic-influenced regimen with maximum discharge between December and April. Oceanic
influence means discharge behaviour coincident with the incoming low-pressure fronts from the
Atlantic. A mix of Oceanic and Mediterranean influence determines the discharge behaviour of the
Rio Aragon. In upper parts the snow influences the regimen with high flows during the thaw-period
in spring. In lower parts the pluvial influence increases and determines the discharge behaviour. The
flows in the period December to April are increasing in comparison to the relation between the
winter and spring flows at the gauging station Canfranc. Momentary the hydrological systems
undergoes profound changes. The progressively recovering of abandoned fields with dense shrub
and forests decreases the run-off generation due to higher interception rates and lower surface run-
off (Beguería Portugués S et al. 2002)
Further downstream the flow regime of the Rio Aragon is strongly influenced by the Yesa reservoir.
The remaining discharge into the Rio Aragon is subjected to the agricultural demand relative to the
actual storage volume. Fluvial-ecological aspects are of secondary order, the ecological flow was set
to be about 8 m³/s but in extreme situations the flow was just about 2 m³/s.
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2.1.4 VEGETATION
Figure 16: Progressively covering fields located in the Sierras Interiores / Aragon Pyrenees
The vegetation lower than 1600 m must be described as strongly influenced by human activities.
The south of the so-called Sierras Interiores, the Inner Depression and the slopes of the Flysch
sector are dominated by cereal agriculture. Since the middle of the 20th century most of the
cultivated fields, predominant located in the slopes of the Flysch sector, were abandoned. As already
mentioned in the previous chapter the abandoned fields were progressively covered by dense shrub
and pine-forest in the process of succession. Some abandoned fields have been re-forested.
Moreover willowed areas have replaced large areas of the cereal agriculture.
Figure 17: Actual vegetation Figure 18: Actual land use
Natural forests are forming wide but not overall coherent areas, which are discontinued above
1400m. Above 1800m the sub-alpine zone of vegetation starts, speckled with small forests of black
pines. Areas with an altitude higher than 2300m have to be assigned to the alpine zone of
vegetation. There, periglacial activities explain the scarcity of plant cover and geomorphic processes
linked to frost-thaw processes. Further downstream connects the Ebro valley. This zone is subjected
to the influence of aridity, as can be seen in most of the area surrounding Zaragoza, which is either
bare or covered by natural desert-like vegetation.
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2.1.5 POPULATION AND ECONOMY
The population in the area of the Pre-Pyrenees shows a strong decreasing trend. In 1950 there
were about 8363 inhabitants registered, in 1981 however, only just 2370. The regional economy is
composed of an agricultural and touristic sector. Above the reservoir in the adjacent hillslopes most
cultivated fields were abandoned since the middle of the 20th century. The fields in the hillslopes are
steep and machines could hardly be used to cultivate them. Differently in the region of Cincovillas,
50 km south of the reservoir, where large areas (around 61000 ha) are industrially cultivated using
modern agricultural methods. The water for irrigation comes from the Yesa reservoir. J.Herrero et
al. (1996) describe the conditions for agricultural activities as follows:
“Winter cereals (barley and wheat) are the only feasible crops to grow on unirrigated lands, and crop
production is often low or nil. Bad production years impact on the whole society, and successive
Spanish governments have responded by increasing the area of irrigated land. Irrigated crops
include: alfalfa, winter cereals, maize, sunflower, deciduous fruit tree, horticultural crops, and rice.
Agricultural production from these lands is an important component of the regional economy.”
ENCUESTA DE POBLACIÓN ACTIVA, 2000

(media anual)
Yesa Reservoir
7,02
25,96
55,06
9,12
Region of
Cincovillas AGRICULTURA INDUSTRIA CONSTRUCCIÓN SERVICIOS
Figure 19: Regional economics of the Spanish Pyrenees and Figure 20: Labour market distribution in [%] for the
the Ebro Valley – brown marked areas are irrigated fields Region of Aragon
From an economical point of view the agricultural sector is a non-profitable business. In recent
years the prices for the cultivated food products were progressively dropping on the world market.
EU-subsidies and artificially low water prices are necessary to secure the survival of the farmers.
The skiing resorts, which were set up in the mountains near Canfranc, and the Santiago’s Way, a
World’s Cultural Heritage, are the most important source of income in the touristic sector.
Throughout the year many people are travelling along the Santiago’s Way, which runs along the Rio
Aragon and the banks of the Yesa reservoir. Along this way there are many hotels and restaurants
and two camping sites are situated at the Yesa reservoir.
2.2 ACTUAL YESA RESERVOIR

The construction of the 47m high dam wall has been finished in April 1959. The opening
celebrations were held by General Franco. The Yesa reservoir has a storage capacity of 471 Hm³. A
bathymetry study in 1986 estimated a remaining storage capacity of 450.3 Hm³ due to sedimentation
(Ministerio de Obras Públicas y Urbanismo 1993). According to the Ministerio de Medio Ambiente
(2000) the total capacity in December 2000 was about 447 Hm³ where 411 Hm³ are utilizable.
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Management
Figure 21: Arial picture of the Yesa reservoir
The reservoir is fed by three inflowing rivers: the Rio Aragon, Rio Esca and Rio Regal. The total
inflow volume of the last named Rio Regal is small in comparison to the other two rivers. The Rio
Aragon has a medium inflow volume of 1019 Hm³ / year (32.6 m³/s) for the years 1959 - 1995, the
Rio Esca a medium inflow volume of 353 Hm³ / year ( 12,1 m³/s) for the years 1951 - 1995.
Figure 22: In- / Outflow streams of the Yesa reservoir (Rio Reral is missing)
The Yesa reservoir is a single-purpose reservoir. The stored water capacity is used exclusively for
irrigation of about 61.000 ha farmland, located nearby in the area called Region Cincovillas. Mainly
the water of the Bardenas Canal, which is directly fed by the Yesa reservoir, supplies this farmland.
The remaining discharge flows into the Rio Aragon, which in turn flows into the Rio Ebro. At the
dam site hydroelectric power is generated just for own consumption.
2.2.1 THE OPERATION OF THE YESA RESERVOIR FROM 1959 TO 2000
The Yesa reservoir is operated according to a constant pattern. Water is stored during the wet and
thaw period to provide sufficient supplies for the dry season when the agriculture is requesting the
highest water demand for irrigation. Figure 23 shows the hydrograph of the storage content with a
peak in June. End of September the reservoir has the minimum content, in dry years sometimes it is
nearly empty.
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Figure 23: Mean inflow and outflow balance of the Yesa reservoir
Executing a cluster analysis three types of management conditions of the Yesa reservoir have been
detected in which the third type, representing a low reservoir content and inflow situation,
exclusively appeared during the period 1990 – 1996 (J. I. López Moreno et al. 2000). This analysis
was used as an opportunity to run further investigations into the possible management practice of
the Yesa reservoir under the conditions of changed flow regimes.
2.2.2 DATA QUALITY
Time series records of daily resolution of the storage volume and in- and outflows of the Yesa
reservoir are available since the start of its operation in 1959. Additional run-off time series with a
daily resolution but with some longer interruptions of the Rio Aragon at the Yesa dam site are
available since 1913. According to information of the IPE Institute / Zaragoza these old records
may include a systematic error in measurement. The in- and outflow data from 1959 – 1996 do not
contain any significant error which could endanger the consistency. In all probability from 1997 the
data of the outflow into the Bardena Canal contain a systematic failure2. Therefore all analysis have
been performed without data recorded after 1996. Furthermore the daily measured storage volume
is of poor quality due to the following reasons:
The reading of the actual water level contains errors due to undulation of the water surface
and reading errors. Specially with high filling levels errors in the range of centimetres are
causing large uncertainties.
Missing records of the inflow from the Rio Regal. The annual balance of the total run-off
volume is small in comparison to the other two inflow rivers. But in daily balances during
heavy rainfall events over Yesa the inflow volume of the Rio Regal cannot be neglected.
Storage volume data collection at 8.00 in the morning, mean discharge between 0.00 and
24.00.
Obliquely positioned water surface due to wind forces
Changing bathymetry due to sedimentation
Furthermore missing records of actual evaporation, precipitation over the Yesa reservoir and the
unknown rate of infiltration complicates a correction of the storage volume.
2 The position of the comma was shifted out of 23.345 became 2.3345
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2.3 YESA ENLARGEMENT PROJECT

For a better understanding of the project’s background chapter 2.3.1 provides a short introduction
into the Spanish water policy from the beginning of the 20th century till today.
2.3.1 SPANISH WATER POLICY
The history of Spanish water policy reaches back to the beginning of the 20th century. Spain lost
its lasts overseas possessions (Cuba, Puerto Rico and the Philippines) in 1898 after a war against the
United States of America. At this time Spain was a backward country with 60% of the people
working in the agricultural sector. The productivity of both land an labor was low (in part because
of poor soils and climatic extremes), there were high levels of poverty and illiteracy. Joaquin Costa,
the leading figure of a social and political movement that wanted “ to reverse the Spanish “race”
through public works, particular irrigation systems”.
To the political parties: Irrigate our fields if you want to leave a memory of your public tenure.
These opening words of Joaquin Costa´s book “La mission social de los riegos en España” (The social
mission of irrigation in Spain) are still nowadays the guideline for the Spanish water policy. Today
the agricultural sector, which employs only 6% of the working population, is no longer the leading
sector of the economy. Spain has “the largest and most complex water distribution network” and a
more than 1196 large reservoirs to supply this network. The agricultural sector consumes about 80%
of the entire water consumption.
The first National Hydraulic Works plan was drawn up in 1902. The aim of this plan was to create
1.5 million hectares of irrigated land, supplied by 205 large hydraulic infrastructure projects. In 1933
the Spanish government approved a new plan called the Pardo plan after its author Lorenzo Pardo,
who considered expanded irrigation as part of a solution to the persistent social conflicts in rural
areas.
Figure 24: Estimated number of large dams worldwide
The Spanish civil war (1936-1939) finished the period of the Second Republic and the dictatorship
under General Franco came into power. In 1939 General Franco designed a new water plan in
which the industrial consumption of water was given a higher priority than to the agricultural sector.
“The 1939 plan failed to meet its goals for irrigation, but the construction of dams to generate electricity went forward
at a feverish pace. As a result, the quantity of water stored in reservoirs rose from 4.2 billions cubic meters in 1939 to
almost 8 billions cubic meters in 1952.”
Before the Franco era water policy was the preferred solution to diffuse social conflicts. Under
Franco water policy acted as one of the major means of legitimising the dictatorial regime.
Nowadays the extensive expansion of the hydraulic infrastructure cannot be continued because
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of exhaustion of the potential sites for new reservoirs and the recognition of the socio-
environmental impacts of large-scale projects.
In 1985 the Water Law was legislated by the Socialist Party which claims a planning at two different
levels, that of the individual river basins and that of the country as whole. The National Water Plan
of 1993 is a reaction to the extreme droughts and flood events in the early nineties; furthermore that
plan is required by the Water Law of 1985.
Although this plan called for greater efficiency in water use as well as a new sensitivity to environmental issues, in the
end it fell back on the old model of expansion through a massive program of new reservoirs and extensive water
transfers.
In the elections of 1996 the Socialist were defeated and the Popular (Conservative) Party came into
power and they shelved the original National Water Plan of 1993. In 2000 the new National Water
Plan passed the parliament. The Popular Party promised to make the water policy more sensitive to
economic, regional and environmental aspects but the plan of the year 2000 is being controversially
discussed. Innumerable manifestations took place, e.g. in Zaragoza with more than 400.000
participants. In particular the projects of traverses with its complete spectra of consequences
generate heavy resistance in the general public and in the affected Spanish Regional governments.
2.3.2 HISTORY OF THE PROJECT
Since the beginning of the seventies the combined regulation of the Rivers Rio Aragon and Rio
Irati were under discussion. The aim of the regulation was to provide additional water quantities for
new irrigation areas. Three optional versions, including new reservoirs and traverses between several
storages, were presented, one included the enlargement of Yesa to a total storage capacity of
1090 Hm³. Because of growing resistance in the population, coincident with the change of Spain
into a democratic system, against all three proposed alternatives the project was virtually cancelled in
1980.
In 1982 a new project was started. This project did not synthesize anything with the first mentioned
project of the seventies. It envisioned the enlargement of Yesa up to a total storage volume of
1525 Hm³, the second largest reservoir in the Ebro basin after Mequinenza (1528 Hm³). After
several modifications the project was presented to the public in November 1986. Hundreds of
objections have been expressed since the publication of the detailed plans. In 1992 the project was
presented again. P. Arrojo et al. (1999) give a good description of the proximate public reaction:
More than 3000 objections were expressed; from everywhere in Aragon, professors of the University of Zaragoza,
approximately hundred communities of the surrounding area, political parties like the Chunta Aragonesista and
Izquierda Unida, all environmental groups from Aragon, etc. None of these objections were answered.
The presentation of the modified plans for an enlargement of the Yesa reservoir was attended by a
campaign “Agua que has de beber”3 with the motto “Recrecimiento de Yesa” . This must be considered as
a direct innuendo to enlarge the Yesa reservoir in order to supply the planned traverse to Valencia
with water. This is in contrary to the present purpose to use the additional water quantities for the
regional consumption for irrigation and the water supply for the City of Zaragoza. Accusations of
corruption against the president of the CHE (Confederación Hidrographica del Ebro), one of the
biggest supporter of the enlargement of Yesa, are burdening the circumstances of this project.
In 1998 the City of Zaragoza, the DGA (Diputación General de Aragón) and the CHE
confirmed a convention to support the Ebro-basin with water from Yesa. In December 2000 several
companies were requested to submit an offer for the enlargement of the Yesa reservoir. The
3 This cannot be translated. The sense this wordplay wants to place that Aragon should provide surplus water to other
regions.
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construction work has not yet started. The project is still in the approval procedure due to many
raised objections requiring additional expert opinions.
2.3.3 VALUATION OF THE PROJECT
The history of the Yesa project reflects all historical intentions on making water policy in Spain
and at this point it is important to cite the opening words of Joaquin Costa one more time:
To the political parties: Irrigate our fields if you want to leave a memory of your public tenure.
Not only the project itself is heavily disputed even the supporters are at odds with each other on
account of the various intentions about the use of the new water quantities. The enlargement of the
reservoir of Yesa has become a political issue with more than regional character. This dispute takes
place across all political levels in Spain, starting with the National Government in Madrid ending
with local communities. Except for the communities directly affected by the enlarged Yesa reservoir
all political institutions on national and regional level are supporters of the project. The strongest
opposition against this large scale project has come from environmentalist groups and unions of
affected people with its umbrella organisation COAGRET (Coordinadora de Organizaciones de
Afectados por Grandes Embalses). Right after the announcement of the project, the opposition
started pointing out to the future negative effects induced by flooding additional landscape.
2.3.3.1 CONTRA-ARGUMENTATION
The Yesa dam, built in 1959, had already flooded the villages Tiermas, Ruesta and Esco. At this time
1439 people had to be displaced, which account for about 24 % of the total drop of the population
in this area. Today the enlargement of Yesa would cause the displacement of additional 400 people,
resident in the villages of Artieda, Mianos and Sigües. According to COAGRET nearly the total
population including public infrastructure in the area between Yesa and Berdun (around 35 km)
would disappear; the remaining village of Salvatierra would be totally isolated. Large areas of the so-
called Foz de Sigües, a protected nature reserve, and 771 ha of ecologically valuable vegetation will
be lost. Additionally the proposed runs of the reconstructed roads will affect areas of high natural
value. Also victim of the Yesa enlargement are objects of high cultural value, i.e. 15 km of Santiago’s
Way (World’s Cultural Heritage) and five Middle Age churches which will be flooded. With the
enlargement of the Yesa dam several camping grounds will disappear. The local tourisms is an
important source of income for the resident population. At the moment the effects on the
development of the future tourism can just be roughly assessed.
Impacts on the microclimate cannot precisely be predicted, but with regard to an expected
evaporation of around 52 Hm³ / year cannot be excluded. Furthermore some expert opinions are in
doubt as to safety aspects. The Yesa reservoir is located within a zone with tectonical activities; hot
springs prove these activities. A geological report (P. Arrojo et al. 1999) draws the conclusion that
the additional weight due to additional water volume increases the seismic risks within this area.
Finally the project’s opposition refers to the poor efficiency of the current irrigation systems and
thus the potential of reducing the demand by improved techniques. The irrigated area of Bardena I,
together with those of Monegros, have the lowest returns and lowest irrigation efficiency (40%) in
the whole of the Ebro valley (COAGRET 2000). There is also the problem of Zaragoza’s water
distribution network, one of the oldest and worst working all over Spain (COAGRET).
Furthermore the opposition refuses various calculated water demands and quotas for human and
agricultural consumption which were used to verify the need of the enlargement of the Yesa
reservoir.
2.3.3.2 PRO-ARGUMENTATION
The pro-argumentation for an enlargement of the Yesa reservoir, lead by the supportive entities,
is based on calculated future and present water demands. The CHE states that the actual
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Management
reservoir is not sufficient to guarantee existing water demands in the agricultural sector. Only an
enlarged storage volume of the Yesa reservoir is able to guarantee sufficient water resource for
irrigation and an ecological flow downstream of Yesa.
Furthermore, the current drinking water supply4 capability of Zaragoza cannot guarantee year-
round water of quality that complies with the EC-Directives, therefore requires additional supply
with water of good quality from Yesa. Recapitulating the above arguments the enlargement of the
Yesa reservoir is necessary to guarantee a maximum reserve of the scarce resource of water. There is
water demand for an envisaged traverse to Valencia that would require respective resources to
support the economy’s growth in the region around Valencia. Finally, an enlarged reservoir would
facilitate the production of additional electricity and better the chances to control high flood events.
2.3.3.3 DISTRIBUTION OF THE ADDITIONAL WATER VOLUME
Precipitation and run-off data show a highly diverse spatial pattern over the Iberian Peninsula.
Moreover this pattern has high temporary variability. At regular intervals drought periods require
higher specification in the distribution of the available water resources. Several traverses are
designated within the actual National Hydrological Plan to balance the existing water deficiencies.
Leandro del Moral et al. (1999) state:
“Humans adaptation to these rather chaotic patterns of precipitation may be the most important aspect of the evolving
relationship between nature and society in the Iberian Peninsula.”
At this point the aspect of the relationship within the society have to be considered too. After many
years of strict central control under the Franco regime the Constitution of 1978 assured the
autonomous regions of more political power towards Madrid. This led to opposition by water-rich
regions to the designated traverses, which transfer part of their resources to water-scarce areas. The
Yesa Project became subject of this struggle on account of different purposes in respect of the
future use of the additional water resources. According to COAGRET (2000) the following
objectives are under consideration:
Newly irrigated areas in the Bardenas II (48.500 Ha) and Bardenas III ( 27.000 Ha) areas.
Supply of the City of Zaragoza and the Ebro Corridor (100 Hm3)
General supply of the Ebro basin
The general supply of the Ebro basin implies that Yesa will deliver water for a nationwide use.
Criticising the actual National Hydrological Plan the government of Aragon expresses their
opposition against the central government in Madrid and their intention to have the water resources
of Aragon largely at their disposal (Gobierno de Aragón 2000).
“The justification for the transfer from the territorial point of view is irritatingly simple, since it consists of
posing the question , in a subliminal manner, as to whether a territory with surpluses is entitled to refuse to
release its surplus water to another territory in need of it. In this approach there is an enormous underlying
fallacy which is precisely in the basic foundation of it effectiveness, since the question takes two things for
granted.
That there are surpluses in the source territory.
That the recipient territory needs this water and, at the same time, has no possibility of getting it within its
own territory.”
4 At the moment Zaragoza covers its drinking water supply from the Rio Ebro
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2.3.3.4 AUTHOR’S CONCLUSION ON THE ARGUMENTATION
The overall political intention of this project is to gain additional water resources, but the future
distribution of the water is still under dispute. The environmental and social effects of the
enlargement of Yesa are grave and will have a massive impact on the local environmental and social
system. In addition there are doubts on the economical profitability. It seems that E. Naudascher
(2001) is right in his philosophic assessment that economy and technology (here: a large-dam project
and the agricultural sector) replace natural values by financial values.
Three types of groupings of interests can be outlined. The first group is mainly composed of the
directly affected local population and environmentalists from all over Spain. They refuse the
enlargement of Yesa due to the above listed negative social and environmental effects. The second
group is a regionally settled group, composed of the Regional Government, the agricultural sector
and the industry. They are interested in the availability of additional water resources but are refusing
the transfer of water into other territories. The third group is the Central Spanish Government and
the other Regions suffering water-scarcity and their respective Regional Governments.
As a preliminary valuation of the pros and cons it must be concluded that a very important
argument within this discussion is totally missing. There is no appropriarte consideration of the
future effectivenes of the performance of an enlarged Yesa reservoir.
Today the Yesa reservoir can be considered as a one-year storage. The total annual volume of the
inflowing rivers Rio Aragon & Rio Esca is on average much larger than the storage volume.
Whereas the enlarged Yesa reservoir cannot be considered as a one-year storage anymore. The
average total inflow volume amounts to around 1300 Hm³, the enlarged reservoir however offers a
storage capacity of around 1500 Hm³. A successful managing strategy of the enlarged Yesa reservoir
strongly depends on the future water availability. The future water availability must be judged
against the background of climate change and change of land-use within the catchment above the
Yesa dam. Already the water availability in the recent decades gives rise to doubts for successful
managing of the additional storage volume. These hydrological aspects were the cause to start
further investigations of the reservoir management with regard to changed water availability.
2.4 MODEL OF THE YESA RESERVOIR

From the previous chapters it can be derived that the enlargement of the Yesa reservoir is a
project of interdisciplinary character. The Yesa project turned into a political issue on the regional
level as well as on the national level. In the previous chapters this study has presented a summary of
the continuous discussion and the actual scientific background of some argumentation.
The purpose now is to take up again a more engineering based approach which has been totally
neglected in the discussion about the enlargement of the Yesa reservoir. It has been argued a lot
about existing water demand quantities and the implementation of water saving programs. But the
aspect of sufficient annual inflow volume into the Yesa reservoir with respect to climate and land-
use change in order to satisfy the water demands has not been given consideration till now. For that
reason a computational model of the actual and enlarged Yesa reservoir was tested against the
known hydrological situation from 1959 –1999 and two future scenarios.
The application of models facilitates a prediction of future situations based on present conditions. A
model is never an exact reproduction of the real system; it imitates the behaviour or copies the
structure of a real system. Due to always prevailing uncertainties a modelling process never delivers
a unique result. Several scenarios are necessary to cover the possible future developments of the
input parameters for the modelling. Therefore the obtained result is a broad range of predicted
conditions, limited by worst and best case conditions. This range facilitates to adapt the present
status of planning to future developments.
In the case of the Yesa reservoir a simulation is able to check the sustainable criteria by quantifying
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the future water resources that are available. The range of the maximum and minimum future water
availability outlines the potential of the enlarged dam to contribute to the improvement of the
human welfare in terms of serving water quotas. The WCD outlines rough conditions which must
be fulfilled to approve the construction of large dams (N. Arnell et al. 2000).
“The WCD concluded that the ‘end’ that any project achieves must be the sustainable improvement of human welfare.
This means a significant advance of human development on a basis that is economically viable , socially equitable and
environmentally sustainable. If a large dam is the best way to achieve this goal, it deserves support.”
Modelling helps to provide a firm foundation of facts on which the process of weighting the positive
against the negative effects can be put on. This report wants to emphasize the need to determine
such a firm foundation in terms of a maximum and minimum water availability for the Yesa reservoir
with the help of modelling technique. This presupposes the estimation of future trends respective to
the effects of climate and land-use change on the run-off generation as well as higher evapo-
transpiration rates.
2.4.1 RUN-OFF SCENARIOS
Remembering the short essay about the history of the enlargement-project the storage volume of
about 1500 Hm³ has been fixed in the early 80ies based on data showing a higher total annual run-
off volume than nowadays. According to studies of S.Beguería et al. (2002) the mean annual run-off
in recent years shows a 30% decrease in comparison to the 1913 – 1959 mean due to land-use
change. This has been confirmed without ambiguity because no climatic trend in the study area has
been detected which could have caused the decrease in run-off generation.
It can be assumed that nowadays the development of the natural vegetation on 60% of the
abandoned fields has come to a point were future developments are not going to have any further
influence on the run-off generation anymore. 40 % of the abandoned fields are still in the process of
impacting on the run-off generation. Also the further development of the soil-system due to the
changing vegetation might have an impact on the run-off generation. Due to a lack of investigations
no further statements about the possible development can be made. A further decrease of the
annual run-off volume up to about 40% is expected till 2050. Presumably after 2050 this trend will
stop.
The second process affecting the annual run-off volume is the possible climate change with the
predicted effect on the run-off generation according to figure 8. N. Arnell et al. 2000 state that
climate change is superimposed on natural multi-decadal climatic variability, and within the next 30
years the effect of climate change in a catchment may be small relative to natural variability,
assuming no non-anticipated changes. Therefore climate prognosis change presented by the
ACACIA project will play an important part in the run-off scenarios to determine a worst-case
scenario. The fact that no significant change in the regional climate has been detected does not
mean that there is no climate. All scenarios show a 10 % to 25 % decrease in average annual run-off.
This negative future trend of the annual run-off volume was the trigger to start further investigation
into the future operation of an enlarged Yesa reservoir under two scenarios:
Scenario 1: assuming a 40% decrease in 2050 of the annual inflow volume into Yesa
reservoir due to land-use changes and a 25% decrease in 2050 due to climate change.
Scenario 2: assuming a 40% decrease of the annual inflow volume into Yesa reservoir due
to land-use changes and a 10% decrease in 2050 due to climate change.
A linear progression of the decrease due to climate change beginning in 1990 and a logarithmic
progression beginning in 1950 has been assumed.
A time series for the hydrological years 2000 – 2050 for each scenario 1 & 2 was originated. For that
purpose the daily values of the recorded times series from 1.10.1979 to 30.09.96, equivalent to 25
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years were modified according to the specifications of the scenario. Interlinking two of the so
modified time series are forming the 50 years time series for the scenario 1 and 2.
A rough estimation of the future water-demand the Yesa reservoir has to supply is more
complicated than the estimation of the possible inflows. Temperature increase of about 1°C might
cause a 5 % - 10 % higher water demand in the irrigation of farmland. On the other hand better
irrigation techniques like trickle irrigation and the cultivation of products with lower water need
could moderate the losses. Therefore the future water demands rather depend on political decisions
than on a higher evapotranspiration due to climate change. But it is certain that higher temperatures
will reduce the economical productivity of a volume unit of water in agriculture. To outflank this
problem the unchanged time series from the 1.10.1979 to 30.09.96 of the outlet flow into the
Bardena Canal was used as a predetermined outflow for irrigation. The evaluation was carried out by
means of the remaining storage volume, which was available for additional consumption.
The shifting of run-off volumes from spring to winter months due to a temperature rise in winter
has not been considered. Strong negative effects on the operation of the reservoir are not expected
because winter is the time where the storage process has started and enough storage capacity is
available to absorb this temporarily shifted water volume.
2.4.2 MODELING OF THE ACTUAL RESERVOIR
The applied model is a simple one-reservoir model making up the temporary balance of the
storage volume according to equation 1:
d (storage volume) / dt =
inflow volume – outflow volume (eqn 1)
introducing discrete time-steps of the length of one day equation 1 can be rewritten as
(reservoir volume)day i+1 = (reservoir volume)day i + (inflow volume) day i +1 – (outflow volume) day i +1 (eqn 2)
The outflow volume is composed of three single flows, in which again the outlet flow into the Rio
Aragon (flow 2) is composed of two sub-flows:
1. Outlet into Bardena Canal
2. Outlet into Rio Aragon
a. Ecological minimum flow
b. Additional outlet flow
3. Outflow volume out of the spillway into the Rio Aragon
Chapter 2.2.1 showed that there are no extensive management (outlet into Bardena Canal and Rio
Aragon and the position of the adjustable contactor in front of the spillway) rules in the operation
of the Yesa reservoir. In the model the outlet into the Bardena Canal is by definition predetermined,
using the original Bardena Canal outflow time series, but the other two flows remain unknown. This
is why the model is not able to predict the exact outflow volume downstream of Yesa using the
inflow information in the period between 1959 and 1996. It just intends to imitate the management
behaviour of the reservoir.
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To implement a model of the Yesa reservoir the position of the contactor was set at a fixed position
equivalent to 422 Hm³ storage capacity. This corresponds to the maximum storage capacity in order
to control floods during autumn and winter. This assumption facilitates to determine the spillway
outflow volume.
The discharge into the Rio Aragon is composed of two flows (flows 2a and 2b). The first flow is the
ecological minimum flow, which was set to be about 8 m³/s. The original outflow time series shows
flows with a lower discharge down to around 2 m³/s, mainly in the late summer months. Therefore
the model reduces the ecological flow to 5 m³/s, approximately the mean of all reduced flows, if the
storage volume falls below 55 % in dry months. The second flow into the Rio Aragon is a variable
flow related to conditions, whose are described by four indices. The value of the second flow is the
product of a fixed basic flow and the four indices according to equation 3:
Qsec.flow = basic flow * Index 1* Index 2 * Index 3 (eqn 3)
The first index relates the monthly mean discharge of the Rio Aragon into the Yesa reservoir to the
1959 – 1999 mean. A lower mean reduces the outlet flow into the Rio Aragon, a higher mean
increases the outlet flow into the Rio Aragon in order to reproduce the natural flow regime. The
second index relates the actual storage volume to the historical mean of the appropriate month. This
reduces the outflow when the available volume runs low. The third index imitates the flow regime
of the Bardenas Canal. Higher flows in the Bardenas Canal cause higher discharge into the Rio
Aragon in order to simulate the water demand in agriculture.
Figure 25: Modelling result versus original data
Furthermore the model increases the outflow into the Rio Aragon when the actual storage volume
exceeds the 80 % of maximum capacity. This makes storage volume for sequencing floods available
and prevents the spillway to be activated with a high frequency.
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Taking the original Yesa inflow and Bardena Canal time series, setting the value of the basic flow
(eqn 3) to be 1 m³/s and applying the above-described model the result shown in figure 25 was
obtained.Figure 25 shows that most of the results in terms of a daily storage volume obtained by the
model are in agreement with the recorded time series of the Yesa storage volume. The higher
maximum storage volume results from the vertically adjustable contactor which has not been
considered in the model. As a consequence the simulated minimum storage volume is lower. The
remaining deviation between model and reality must be attributed to poor quality of original data
(refer to chapter 2.2.2), extraordinary circumstances, loss of storage capacity due to sedimentation
and non-conformity in the reproduction of the management rules in detail.
2.4.3 HYPOTHETICAL ENLARGED YESA RESERVOIR FROM 1959 TO 19955
This chapter is to discuss the question how an enlarged Yesa reservoir with a storage volume of
about 1500 Hm³ could have been operated during the period 1959 – 1999. Again the model,
described in the previous chapter, was strained with the original Yesa inflow and Bardena Canal
time series. The basic flow was set to be 12 m³/s, which is not equivalent to the twelve fold
operating efficiency. Comparing the total volumes of the second flow (flow 2b) into the Rio Aragon,
estimated by equation 3, of both simulations (regular Yesa and enlarged Yesa) the three-times larger
Yesa 1500 reservoir produces just about 30 % more second flow, which can be considered as a
measure of capability. Figure 26 shows the obtained results in terms of daily storage volume.
Figure 26: Hypothetical enlarged Yesa reservoir from 1959 - 1996
A periodically decreasing trend with years of recovery (1978 and 1993) can be indicated. But it
can be seen that each wet year generates less run-off to fill up the reservoir to the initial storage
volume of the previous period. During the hydrological year of 1978 the storage volume exceeded
the 1400 Hm³ line for the last time. In the last 20 years the 1200 Hm³ line must be considered to be
the maximum storage level due to changes in the hydrological system in the catchment (change of
land-use). Remembering the history of the project the planning process started in the early 80ies,
5 Simulation had to be stopped end of the hydrological year 1996 on account of defective Bardena Canal outflow and Yesa
storage volume data
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where the enlarged storage volume of about 1500 Hm³, based on the analysis of time series recorded
before, was dimensioned.
The results shown in figure 25 are a very strong indication that the storage volume of 1500 Hm³ is
totally overdimensioned as a result of the land-use changes having taken place within the
hydrological system of the Rio Aragon.
2.4.4 FUTURE YESA RESERVOIRS
The process of land-use will continue and certainly be intensified by climate change effects. The
previous chapter showed that already nowadays an enlarged storage volume would be
overdimensioned from the hydrological aspect. Two scenarios have been designed to simulate the
operation of the Yesa reservoir till 2050. Figures 26 and 27 show the obtained results for the future
scenarios.
The results (scenario 1 and scenario 2) for the actual Yesa reservoir with a maximum storage
capacity of 411 Hm³ indicate serious problems to provide the required water demand in the future.
These problems already have been experienced in the recent years, e.g. 1988 where in August the
average discharge into the Bardena Canal was reduced to 26.6 m³/s in comparison to 49 m³/s in
1959 – 1997.
Also the enlarged Yesa reservoir is not able to provide sufficient security for the demanded water
volume in both scenarios. The simulation of Yesa 1500 for the Years 1959 – 1999 showed that the
remaining water volume, stored in wet years, the reservoir had sufficient supply to fulfil the water
demand quotas for a following very dry year. This absorbing capability is disappearing and every dry
year becomes a time of shortage.
Figure 27: Future Yesa 1500 Hm³ reservoir
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Management
Figure 28: Future 411 Hm³ Yesa reservoir
2.4.5 CONCLUSIONS
Increasing the maximum storage capacity is not equivalent to increasing the available water
volume. This has clearly been shown in the above-presented simulations of the Yesa reservoir with
two storage capacities. The future and the actual annual run-off volume of the Rio Aragon
catchment are not sufficient to fill the enlarged reservoir. The enlarged reservoir is overdimensioned
under the present and future existing hydrological conditions.
On the other hand increasing the storage capacity and keeping the water demand quotas constant
would increase the security to fulfil the existing demand. The intention to increase the available
water volume and the security of water supply by enlarging the Yesa reservoir must be rejected as
not achievable. Even the fulfilment of the actual demand in the future with an enlarged reservoir is
not secured.
The preceeding modelling has to be considered as a first, preliminary study. All utilized bases and
assumptions of the model are rough estimations, but the very strong trend in the results towards
water scarcity emphasizes the need for further investigations and resolution.
2.5 CHANGING OF THE YESA SYSTEM

The Yesa system is defined as being composed of two different areas. From a hydrological point
of view the first area can be defined as the catchment of the Yesa reservoir, as shown in figure 15.
Here the decision to construct the Yesa reservoir has already caused great impact with profound
changes in the socio-economic system as well as in the ecological system; particularly in terms of
the flow regime and the aquatic ecosystem of the Rio Aragon. The possible decision to enlarge the
Yesa reservoir will cause again profound changes in the socio-economic and ecological system. A
third impact is the predicted global climate change with effects on the management of the Yesa
reservoir and the sensitive ecosystems of the high alpine zone as well as the aquatic ecosystem.
The second area is defined to be the water receiving area, located downstream and called Cincovillas
(refer to figure 19). The agricultural sector is totally dependent on the water supply provided by the
Yesa reservoir due to the arid climatic conditions which requires irrigation systems. Every change in
the hydrological source system have effects on the socio-economical system downstream.
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2.5.1 SOCIO-ECONOMICAL SYSTEM
In general the construction of the Yesa dam had a positive effect on the socio-economic of the
water-receiving area and negative effects within the catchment area. An extensive analysis of
possible positive and negative social impacts during the living phases of large dams was prepared for
the WCD as part of its information gathering activities. An extract is shown in figure 28.
Figure 29: Part of an indicative framework for the analysis of equity and distribution issues associated with large dams
The most profound social impacts on the catchment are occurring particularly during the
construction phase of the dam site. The construction has been completed in 1959. The positive
effect of additional construction jobs and increased local economic activities were of short-term
duration. After the dam and all other structure works were finished this effect became shallow.
More than 1400 people were displaced (COAGRET 1999) followed by a further decrease of the
population in the area. The newly created reservoir facilitated fishing activities, reservoir navigation
or recreation activities to strengthen the local tourisms sector. But this additional potential to
develop tourism was not able to stop the migration.
The planned enlargement of the Yesa reservoir would flood the villages of Sigües and labour land of
the villages of Artieda and Mianos. This will cause again the displacement of additional 400 people
(COAGRET 1999) and remaining villages around Yesa become isolated. Maintaining the social
infrastructure like health services, communication or cultural activities would be more complicated
or impossible. The consequence will be that more people, particularly the younger generation, will
emigrate to the cities; the old generation will remain. The WCD (2000) states that most of the
resettlement programmes have focused on physical relocation rather than the economic and social
development of the displaced. Furthermore the enlargement of Yesa will destroy some kilometres of
the Santiago’s Way and five Middle Age churches (COAGRET 1999), a cultural and touristy loss.
People far away form the Yesa reservoir in the areas of Cincovillas, Zaragoza or Valencia would
receive most of the economical benefits in terms of additional water resources.
Mostly affected by the climate effects, with lower precipitation and higher temperatures, is the
agricultural sector of the downstream area of Cincovillas. M.L. Parry (2000) evaluates the effects for
the agricultural sector in the southern countries of Europe as follows:
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In the southern areas the benefits of the projected climate change will be limited, while the disadvantages will be
predominant. The increased water use efficiency caused by increasing CO2 will compensate for some of the negative
effects of increasing water limitations. The possible increase in water shortage and extreme weather events may cause
lower harvestable yields, higher yield variability and a reduction in suitable areas of traditional crops. The increase in
water shortage may be caused by reduced rainfall, higher evapo-transpiration and reduced availability of irrigation
water.
Higher temperatures increase the evapo-transpiration rates and therefore the water demand. This
implies a lower profitability per hectare of land. The already existing problem of salinity will become
worse due to higher evapo-transpiration. J. Herrero et al 1996 state that growing rice may improve
soil salinity, but the higher water application within the range 14,000 to 16,000 m³/year will
additionally increase the pressure upon the shrinking Yesa water resources. Already now many fields
are cultivated with rice. In general the socio-economical development of the Cincovilla region
strongly depends on the future water availability.
In the touristic sector mostly the ski resorts will be affected by higher temperatures and lower
precipitation. F. Zimmerl (2001) carried out an investigation regarding the effects of climate change
on winter tourism in Kitzbühl, a traditional ski resort in Austria. Temperature already shows a
positive trend. Under two future climate scenarios the days potentially usable for ski-tourism
decrease and the ski areas becomes less attractive due to worse snow conditions. This causes a
decrease in tourist overnight stays between 20 % and 27 %. (F. Zimmerl 2001). Finally the human
health could be affected due to spreading of infectious diseases, chiefly in areas close to the
reservoirs.
2.5.2 ECOLOGICAL SYSTEM
As an introducing comment it is beyond the scope of this report to mention all the possible
negative environmental effects due to large dams which have been elaborated on by Bergkamp et al.
(2000). Reviewing the available material with regard to impacts on the ecological systems due to the
actual or enlarged Yesa reservoir no comprehensive studies are available. Therefore just qualitative
statements about the actual or future condition of the aquatic ecosystem can be made.
The main ecological systems are the aquatic system of the Rio Aragon, the ecosystem of the
Pyrenees, particular high sensitive ecosystem of the alpine life zone and the man made ecosystem of
the reservoir. Climate change affects all ecosystems, the construction and future enlargement will
affect or already has affected the aquatic system and flow regime of the Rio Aragon. But on the
other hand the construction of the dam has created a man-made lake, which is a new ecosystem
totally different to the adjacent ecosystems. The construction of a dam has downstream as well as
upstream effects on the river system. The most negative effect of a dam for the aquatic ecosystem
and ecosystem close to the shore is the adjustment of river flow regime; subesequently producing
negative effects on the quality of water. Furthermore dams prevent broodstocks from reaching their
spawning grounds during the breeding season, resulting in massive failure of recruitment and
eventual extinction of the stock above the dam. Global estimates of endangered freshwater fish
reach 30 % of the known species (Bergkamp et al. 2000). The regulation of the flow regimes reduces
the flood intervals downstream, which causes a reduction in groundwater recharge and in removal
of parasites by natural flooding. Reductions in sediment transport is leading in several deltas to
coastal erosion between 5 and 250 m/year, requiring millions of dollars investments in coastal
defence (Bergkamp et al. 2000). Reduced sediment transport already has caused a retreat of the
Ebro-delta.
A positive impact on ecosystems could be the creation of reservoir, which has lead in several cases
to the development of productive and species-rich riparian ecosystems along reservoirs. But in many
cases the habitat gains in and around the created reservoir do not compensate nor outweigh the loss
of habitats either upstream or downstream. The actual Yesa reservoir already has flooded 2089 ha
land; the enlarged dam would inundate about 4804 ha additional land. COAGRET (2000) describes
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the environmental impact as follows:
A large part of the Foz de Sig, protected by Decree 85/1990, will be flooded. 771 ha of vegetation, including 69 ha
of riparian vegetation, which is of outstanding ecological interest, will disappear. There will be serious alteration to the
landscape in an area of growing tourist potential, with enormous quagmires in the summer. The habitat of
lammergeyers and other protected birds will be seriously affected.
Now the effects of climate change on relevant ecosystem for Yesa will be discussed. In general
reduced water availability will have an effect on the composition for ecosystems. The ecosystem of
the alpine life zone is the most sensitive of all with respect to climate change. Recent predictions of
atmospheric warming may lead to drastic changes of the biosphere’s pattern. All ecosystems will
experience climate changes, but ecosystems of the alpine zone are considered to be particularly
sensitive to warming because they are determined by low temperature conditions. This ecosystem
reacts very sensitive to changes in temperature and snow cover. If the temperatures are rising the
species will climb to higher altitudes; some species up to 4m per decade. If the climate change is too
fast some species are not able to keep the velocity of changes and will die on a large scale (F.
Zimmerl 2001). The forests of the Pyrenees are subjected to climate change effects, too. Higher
temperatures and lower precipitation will enhance the danger of forest fire, particularly during the
summer months. Insect and pest population are expected to increase but the extent to which they
may be held in check by natural enemies or may require management control is not known. But
momentaryly the forests of the Pyrenees are subjected to a man-made process. Abandoned fields are
in a stage of recover towards pine forests.
Figure 30: Forest fire and the Yesa system
The aquatic ecosystem of the Yesa system will be affected by climate change, too. According to the
climate scenarios presented by ACACIA the run-off will decrease and this effects the aquatic system
as well as the vegetation immediately at the river banks. Higher water temperature can be expected
due to lower run-off and higher air temperatures. This has a negative effect on the water quality and
consequently on the aquatic ecosystem. Furthermore the lower run-off volume into the Yesa
reservoir will increase the conflict between the outflow into the Rio Aragon, in order to guarantee a
minimum ecological flow, and the outflow into Bardena Canal to meet the water demand for
irrigation. In the recent years the minimum outflow was set to be 8 m³/s, reduced in times of
extreme water scarcity. For the enlarged Yesa reservoir, however, the ecological flow was reduced to
5 m³/s (CHE 2000).
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COMPLEX 3 : STRATEGIES AGAINST CLIMATE CHANGE
In the days before “global climate change” all planning processes were carried assuming that the
relevant characteristics will be similar to those of the recent past. But climate change has turned this
“stationary world” into an “instationary world” because it has the power to change socio-
economical, ecological and hydrological characteristics globally as well as locally. Preventive
measures try to keep the world climate in a stationary condition. Measures of adaptation, however,
intend to prepare the natural system for the effects of the “instationary world”. Many adaptations
have the potential to reduce adverse impacts of climate change and to enhance beneficial impacts,
but will cause cost and will not prevent all damages. The ability of human systems to adapt to and
cope with climate change depend on such factors as wealth, technology, education, information,
skills, infrastructure access to resources and management capabilities.
3.1 HISTORY OF INTERNATIONAL CLIMATE PROTECTION
In 1898, Swedish scientist Svante Ahrrenius warned that carbon dioxide emissions could lead to
global warming but it was not until the 1970s that scientists developed an understanding of the
atmosphere.
During the “United Nations Conference on Environment and Development” (Rio de Janeiro, 1992)
154 nations signed “The United Nations Framework Convention on Climate Change”. The aim of
the convention is the stabilisation of greenhouse gas concentrations in the atmosphere on a level,
which enables to prevent dangerous anthropogenic disturbances of the climate system. In 1997 the
1992 framework of climate was supplemented by the Kyoto-Protocol, which includes obligations
for the Industrial Nations to reduce the emission of greenhouse gases. 55 Industrial Nations causing
altogether 55 % of the worldwide greenhouse gas emissions have to sign the Kyoto-protocol so that
it comes into force; Third World countries are held to take actions on voluntary base.
The majority of the Industrial states, which have signed the Kyoto protocol, acknowledge the
reports of the IPCC to confirm the scientific base on climate change. The IPCC released its First
Assessment Report in 1990 and was approved after “ a painstaking peer review process by hundreds
of leading scientist and experts” and “ had a powerful effect on both policy makers and the general
public and strongly influenced negotiations on the Climate Change Convention.” (United Nations
Environment Programme 1997). Despite the scientific background providing sufficient facts to
predict massive climate change in the natural system, within the world community of states there is
no agreement about measures to be taken against the threatening climate change. On the one hand
there are the nations fearing for their economical development, on the other hand many nations
tend to focus on vulnerability and negative impact on their economies. For example, China and
others have enormous coal resources that are vital to their economical development. The AOASIS
(Association of Small Island States) are particularly vulnerable to the risk of sea level rise.
In 2001 the Conference of Parties to the Framework Convention on Climate Change (COP 7) was held in
Marrakesh / Morocco. The central result were the “Marrakesh Accords” a package of 15 decisions
concerning the arrangement and implementation of the Kyoto Protocol. Most states of the world,
among them the European Union, Eastearn Europe countries including Russia and Japan are willing
to ratify the Kyoto protocol against this background till the World Meeting for Sustainable
Development in South Africa in September 2002; the United States will refuse this agreement With
that the prerequisite of 55 Industrial states with 55 % of the worldwide emissions would be fulfilled
in order to let the Kyoto Protocol come into force. It would open a new era of international climate
protection because it would be the first time that states commit themselves according to
international law to reduce the emission of greenhouse gases.
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3.2 GLOBAL STRATEGIES AGAINST CLIMATE CHANGE AND ITS

EFFECTS
The only strategy to stabilize the world climate is the reduction of greenhouse gas emissions. The
Kyoto Protocol designates a 5% reduction of the 1990 greenhouse gas emissions level till 2008 –
2012. Science is aware of the fact that the present results, which were reached during lengthy
international negotiations of the last years, are not sufficient; further reductions have to be agreed to
avert or lower the negative impacts of possible climate scenarios on the natural system. For the time
being the Kyoto Protocol provides four flexible instruments to reach the reduction of greenhouse
gas emissions.
States which have ratified the Kyoto Protocol can form groups, so-called bubbles, in
order to reach commonly the reduction. Within the group the emission rates of each
member may be negotiated.
The Kyoto Protocol allocates quotas of emissions to every participating industrial state.
These quotas can be sold to others states requiring additional quotas of emissions.
The principle of Joint Implementation facilitates industrial states to achieve additional
emission quotas for the own use. Therefore they have to invest in projects, which are
aimed on the reduction of emissions and located abroad in other industrial countries.
The next possible way to achieve additional emission quotas is the Clean Development
mechanism. Therefore industrial states have to participate in climate protection projects
in Third World countries.
Finally the Kyoto Protocol contains the regulations to consider the integration of carbon into
national ecosystems like forests or soils (so-called sinks of carbon) in terms of the allocation of
additional emission quotas.
3.2.1 PROSPECTS
The Kyoto Protocol is the international framework for preventive climate protection. But the
extent of the planned reduction of greenhouse gas emission was more a compromise in favor of an
economically acceptable redcution than desirable from the scientific point of view. The Hans Seidel
Stiftung (2000) describes four fundamental problems for an extensive climate protection.
There is not state, except the AOASIS states, where the public is sufficiently sensitive with
regard to the negative effects of climate change in order to accept far reaching measures.
Many effective measures to reduce the emissions would have negatively short-term effects
on the economical development and therefore would impair the problem of
unemployment; one of the main publicly focused problems.
Even if one or a group of Industrial States would seize further measures to reduce their
emission quotas, they would remain isolated within the international arena.
The Hans Seidel Stiftung (2000) does not see a real consensus within the group of the most
important protagonists with regard to farther reaching measures of climate protection.
Therefore the prerequisite for an international consensus including the Third World
countries is missing.
The problem of the prevention becomes more difficult due to the existing uncertainties
with regard to the effectiveness of the measures to be seized. Still the scientific
understanding of the climate system is not sufficiently comprehensive to estimate the
necessary reduction of emissions to reduce or lower the global warming.
Despite of the here presented problems the earlier actions will be undertaken, including a portfolio
of emission mitigation, technology development and reduction of scientific uncertainty, the more
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increases the flexibility in moving towards stabilization of the world climate system. It must be
noted that despite the reduction of scientific uncertainty the climate decision making will remain a
sequential process under general uncertainty.
A framework for measures necessary to reduce or lower the global warming and consequently the
negative effects of the climate change has to be agreed upon by an international community of
countries that includes the emitters of most of the greenhouse gases. The Kyoto Protocol represents
the first framework for climate protection. But the degree of the intended reduction of greenhouse
gas emissions is seen to be insufficient to avert global warming. Additional measures have to be
seized in order to lower the risks and costs caused by climate change.. As a first step possibly socio-
economical and ecological effects ranging from international to local significance have to be
identified as a starting point for a decision making process.
3.3 LOCAL STRATEGIES AGAINST CLIMATE EFFECTS

Strategies of adoption can be developed on a local level to preserve the socio-economical and
ecological system. Every global strategy leads to local measures, too. But due to the global
dimensions of the climate system every local preventive strategy without a nationwide or better a
global coordination program, like the Kyoto protocol presented in chapter 3.2, would be ineffective.
Therefore this report wants to confine itself to corresponding local strategies.
Chapter 2.5 presented a summary of possible socio-economical and ecological effects for the Yesa
system. In this context it has to be noted that the future development of the Yesa system will not
only be influenced by climate change but also by land-use changes. Chapter 1.3.3 states that
momentarily the land-use change has a greater effect on the reduction of the total inflow volume
into the Yesa reservoir than the climate change. A rough estimate of the future performance of the
actual Yesa reservoir as well as the enlarged Yesa reservoir showed hardly encouraging results. The
actual size of the reservoir will not be sufficient to guarantee the momentary water demand never
mind the additional one. On the other hand the simulation showed that the three-times increased
storage volume of the Yesa project is overdimensioned due to decreasing run-off volume; it never
run full and in the period 1950 – 1996, it would have just provided theoretically around 30 % more
water resources in comparison to the actual Yesa reservoir. Furthermore in simulations of future
scenarios the effect of increased storage volume is rated even less efficient than in the period
mentioned above (refer to Chapter 2.4.4.)
3.3.1 AREAS OF CONFLICTS
Summarizing the facts, decision makers are confronted with the following scenario for the future
Yesa system:
An increased water demand faces a decreased water availability
Possible measures of adaptation have to consider the existing areas of conflicts. Therefore this
chapter is to systemize these areas of conflict in order to embed them into the complete spectrum of
the issue.
Water has an overall meaning for the socio-economical development of the Region of Cincovilla.
This water demand is covered by the water supply provided by the Yesa reservoir. Here the overall
area of conflict becomes visible. It can be summarized to an upstream – downstream conflict. With
regard to the dispute concerning the national distribution of additional water resources, as described
in chapter 2.3.3.3, the local area conflict can be expanded to a national area conflict between surplus
regions and regions suffering water scarcity. But the further discussion will focus on the local
conflict between Cincovilla and the Yesa catchment and not go into this national issue.
To overcome the expected difficulties in water supplies either a demand-management based or

supply-management based solution has to be found. Solutions between both extremes are
39
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possible, too. As a result, two new areas of conflicts can be identified. A supply-management based
solution presupposes an increase of water availability. For the Yesa system that could be an
enlargement of the Yesa reservoir. Like most of the supply-management based solution this causes
profound conflicts with environmental and social aspects. Demand-management based measures,
however, cause less environmental or social problems. But often they run into politically installed
barriers. The investment for a more efficient irrigation system, for examples, is often unprofitable
for the farmers due to artificially low water prices and subsidies for agricultural products.
3.3.2 SUPPLY-MANAGEMENT BASED SOLUTION
According to current planning the preferred solution is exclusively a supply-management based

measure. The enlargement of the Yesa storage volume should increase the water supply capability as
well as the reliability of water demand quotas. The planning does not contain any demand-
management based elements, which would increase the efficiency of water use. The simulations for
the reservoir already enlarged in 1950 showed an additional water availability (equal to the total
sum of the flow 2b over the period) of only 5045 hm³ by 1999. For the period 1999 to 2044 the
further increase would be to 500 Hm³ (scenario 1) respectively 820 Hm³ (scenario 2).
The total costs for the project are estimated at 141.5 Mill €. This includes cost of replacing large
parts of the existing regional technical infrastructure due to the rise of the maximum water level, e.g.
about 20 km of the national road N-240, which runs along the Yesa-reservoir, must be relocated as
well as local supply and communication lines. Applying a simple straight-forward calculation the
investment on a “per m³ base” for the additional water volume would result at 0,03 € / m³ for the
period till 1999, for the period 2000 – 2044 in case of scenario 1 at 0.28 € / m³ and for the period
2000 – 2044 in case of scenario 2 at 0.17 € / m³ respectively. In comparison to that the mean water
price for irrigation amounted to 0.004 € / m³ (equal to 0.67 Pesetas) in 1999 (Instituto Nacional de
Estadistica 1999), the highest price was noted at 0.09 € / m³ in the Región de Murcia.
Table 2: Spanish water prices in 1999
This simple straight-forward calculation showes that the current water price for agricultural
consumption would not even be sufficient to cover the cost of the investment only. Additional cost
resulting from the operation, i.e. staff, maintenance etc. were neglected. Furthermore the given total
cost for the project contains great uncertainty like for all large projects. According to investigations
the WCD (2000) concluded that “large dams in the Knowledge base have marked tendency towards
schedule delays and significant cost overruns.” And finally “large dams designed to deliver irrigation
services have typically fallen short of physical targets, did not recover their cost and have been
40
Management
less profitable in economic terms than expected”. The more intensively the future decrease in run-
off will occur the less the higher the non-profitability of this project will be. Even hydrological
conditions similar to those of the recent past (1950 – 1999) would not facilitate project economics
of an increased Yesa reservoir.
Therefore measures to increase the generation of run-off within the Yesa catchment, are not able to
guarantee an increase in profitability. Re-cultivation of the abandoned fields could strengthen the
social structure, but the low profitability of the cultivatable crop due to poor soils and the hilly relief
and the low number of population thwart this measure in its efficiency. On the other hand,
chopping down the vegetation on a large scale would be costly because it requires a lot of man
power and has to be repeated frequently. Apart from the cost, this radical measure would massively
amplify the sedimentation of the reservoir.
Always a necessary measure to increase the efficiency in the operation of the actual reservoir as
well as the enlarged reservoir is the modernization of the management facilities. At the moment no
meteorological information system is used to gain short-term as well as long-term weather forecasts.
In combination with such meteorological system a “precipitation / run-off generation” model
should be implemented. More precise short-term as well as long-term hydrological information, i.e.
expected inflow volume and evapo-transpiration losses, facilitate the optimisation of the reservoir’s
operation strategy as well as the adaptation of the irrigation system towards available water volume.
Chapter 2.1.3 showed that snow has a very strong impact on the flow regime especially during the
thaw period in spring and early summer. More detailed information about the snow conditions up in
the mountains would reduce the uncertainties about the available storage volume in June, equivalent
to the annual peak of water storage. The earlier the June-maximum can be estimated the more time
remains for the agricultural sector to adopt itself to the expected situation of water supply during the
summer months, especially in case of water scarcity. Furthermore operating the reservoir with the
support of modern computational systems enables to handle different hydrological conditions (e.g.
extreme flood events) outside those for which the actual Yesa reservoir is currently built and
operated. In order to run this model the continuous availability of meteorological and hydrological
data must be guaranteed by a network of measuring stations to be established or to be extended in
the Yesa system as follows:
a. Extent the network of existing meteorological measuring stations in order to gain more
details about climate data (precipitation, wind, temperature, evapo-transpiration etc.) in the
catchment area of the Yesa reservoir as well as in the region of Cincovilla.
b. Establishing a network of measuring stations for snow heights
c. Establishing a gauging station at the mouth of the Rio Regal
3.3.3 DEMAND-MANAGEMENT BASED SOLUTION
The current planning does not feature any demand-management based solution. According to the
WCD (2000) the conventional approach to water resource management known as “predict and
provide” has been replaced by demand-site approaches. “Demand-driven approaches include
attempts to encourage more efficient water use through water pricing and by treating water as a
commodity, as recommended in the World Bank’s (1993) policy paper on water management” The
extreme low water prices in comparison to most of the other Spanish regions prevent any
investments into the modernisation of irrigation systems. As already mentioned in chapter 2.3.3.1
the contra argumentation responds to the poor efficiency of the current irrigation system. Modern
demand-management is not only based on technical solutions like trickle irrigation systems or the
reuse of wastewater. Water pricing mechanism and river-basin integrated water resource planning
are organizational measures for a sustainable development of the ecological as well as socio-
economical sector. These general frameworks have to coordinate water-relevant planning and
decision making processes on a local, regional, national and European level. Political guidelines and
41
Management
tendencies will have a great impact on the further local development of the Yesa system. As long as
subsidies for agricultural products and water for irrigation distort the real cost – benefit relation a
clear economical valuation of the Yesa enlargement project is impossible. But it would be beyond
this report to go into the particulars of the ongoing discussion on the National Hydrological Plan,
the National Irrigation Plan and finally the European Politics of subsidies for the agricultural sector.
42
Management
SUMMARY
Climate variability is a natural phenomenon, yet current scientific investigation shows that there is
the existence of anthropogenic influences on the climate system. Despite of existing uncertainties
GCMs are powerful instruments to predict future climate scenarios. Global climate change may
inflict devastating changes within the socio-economical and ecological system.
The Yesa-system was analysed with regard to current and future socio-economical, hydrological as
well as ecological conditions. It was shown that the development of the Yesa-system highly depends
on water supply. All climate scenarios are showing for the project area increased temperatures, no
change or just slight changes in the precipitation pattern during winter months and a decreased
precipitation pattern during summer months. These changes have the effect of a 10 % to 25 %
decreased run-off generation in the 2050s. According to the analysis of regional time-series no
significant trend neither in temperature nor in precipitation was detected. Run-off time series,
however, show a 30 % decrease; without question this negative trend was related to massive land-
use changes within the catchment area of the Yesa reservoir.
According to current planning the enlargement of the Yesa reservoir shall provide additional water
supply. The contra-argumentation is mainly based on negative effects within the local social-
economical and ecological system; an analysis of the future performance of the projected enlarged
Yesa reservoir under changing hydrological conditions is missing. Therefore the future performance
under two scenarios as well as the theoretical performance of a storage volume, enlarged already in
1950, for the 1950 – 1999 hydrological conditions were simulated applying a simple reservoir model,
based on daily storage balances. The additionally gained water supply is small in comparison to the
increased reservoir size.
Global climate change and the enlargement of the Yesa reservoir will cause profound changes
within the Yesa system as presented in chapter 2.5. According to the pro-argumentation the
enlargement of the Yesa reservoir is a necessary measure to support the socio-economic
development of the regional agricultural sector. On the other hand in case of the project’s approval
high social, cultural and ecological cost are expected – a typical example for the omnipresent conflict
between economical and political interests on the one side and a sustainable development on the
other side. Even from the economic analysis of the modelling results, in terms of additional water
resources, doubts have risen with regard to the economic viability of the project. First, the calculated
water price is much higher than the current water price, which however is kept artificially low.
Secondly the development of the agricultural sector highly depends on EU-subsidies. This shows
that the decision making process is strongly impacted by political conflicts regionally within Spain,
by EU-subsidy policies and economical lobbyism.
Chapter 3.3 discusses alternative solutions, which can ensure socio-economic development as well
as sustainability under the effects of climate change and land-use change. The introduction of
meteorological and hydrological forecast systems are proposed to increase the effectiveness of the
today’s reservoir operating. These measures are aimed at a more effective use of the present water
supply, especially in the agricultural sector. Demand-management is not only based on technical
solutions like the modernisation of irrigation systems. The issue of distorted pricing due to
subsidizing of irrigation water and crops requires new policies and political structures in order to
ensure a sustainable development.
43
Management
CONCLUSIONS
The valuation of the facts and the results of the simulation comes to serious doubts with respect to
sustainability. The Yesa enlargement project is still in the stage of planning, therefore a
comprehensive assessment should be carried out according to the proposed guideline presented by
the WCD (2000):
There are many dam projects today at various stages of planning and development. It is never too late to improve the
outcomes of projects – even ones this large in scale and scope. Dams and Development calls for an open participatory
review of all ongoing and planned projects to see whether changes are needed to bring them into line with the WCD
strategic priorities and policy principles. In general, regulators, developers and, where appropriate, financing agencies
should ensure that such a review:
uses a stakeholder analysis based on recognising rights and assessing risks, in order to identify a
stakeholder forum that is consulted on all issues affecting them.
enables vulnerable and disadvantaged stakeholder groups to participate in an informed manner.
includes a distribution analysis to see who shares the costs and benefits of the project.
develops agreed mitigation and resettlement measures to promote development opportunities and benefit
sharing for displaced and adversely affected people.
avoids, through modified design, any severe and irreversible ecosystem impacts
provides for an environmental flow requirement, and mitigates or compensates any unavoidable ecosystem
impacts
designs and implements recourse and compliance mechanisms
This process of review implies added investigations or commitments, the re-negotiation of contracts and the
incorporation of a Compliance Plan. But additional financial costs will be recouped in lower overall costs to the
operator, to government and to society in general as a consequence of avoiding negative outcomes and conflicts.
The here presented simulation must be regarded as a preliminary study of the future performance of
the Yesa reservoir under scenario-dependent inflow volume and water demand quotas. More
comprehensive studies should be adopted for the assessment of future recourses and risks. These
studies should be scenario-based and not rely on historic climatic and hydrological statistics. The
impacts of global climate change must be seen in the context of land-use changes affecting reservoir
reliability, such as changes in water demand, efficiency of use and operation, and organisational
characteristics.
44
Management
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Challenges For Regional Development Under The Impact of Global Climate Change

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Challenges for Regional Development under

the Impact of Global Climate Change

The Yesa Reservoir in the Spanish Pyrenees as an example

Author: Axel Winterscheid

Darmstadt University of Technology / Institute of Hydraulics and Water Resources Engineering

I want to thank J. M. García Ruiz and López-Moreno J. I. for the

COMPLEX 1 : CLIMATE PROGNOSIS

1.1 THE CLIMATE SYSTEM

Cryosphere is composed of inland ice, glaciers, snow fields and permafrost.

Lithosphere is defined as the Earth’s crust and upper mantle of rocks.

The topmost layer of the soil is called the Pedosphere.

Figure 1: The Natural Earth system

1.1.1 LARGE SCALE OSCILLATION SYSTEMS

Figure 2: Surface temperatre changes between 20°N Figure 3: El Niño phenomenon

1.1.2 GLOBAL CLIMATE CHANGE

1.1.3 EFFECTS OF CLIMATE CHANGE

1.1.3.1 SOCIAL AND ECONOMIC SYSTEM

infectious diseases like Malaria or Cholera.

1.1.3.3 SOIL AND LAND RESOURCES

1 More information available under (http://www.gloria.ac.at)

1.1.3.4 WATER RESOURCES AND RESERVOIRS

1.2 CLIMATE MODELS

Statistical downscaling: Applying regression methods, circulation typing schemes and

1.2.2 EMISSION SCENARIOS

Figure 4: The four SRES scenarios of the IPCC

B1 / Global Sustainability: Here a high level of environmental and social consciousness

B2 / Local Stewardship: Environmental problems will be solved by applying longer-term

B1-low 1.5 491 0.97 13

B2-mid 2.5 502 1.58 37

A1-mid 2.5 547 1.63 38

A2-high 4.5 572 2.64 68

1.3 CLIMATE PROGNOSIS IN THE SPANISH PYRENEES

COMPLEX 2 : THE YESA SYSTEM

2.1.1 TOPOGRAPHY AND GEOLOGY

Figure 13: Topography Figure 14: Geological units

2.1.3 HYDROLOGY AND FLOW REGIMEN

Figure 15: Network of gauging station in the Yesa system

Figure 17: Actual vegetation Figure 18: Actual land use

2.1.5 POPULATION AND ECONOMY

ENCUESTA DE POBLACIÓN ACTIVA, 2000

2.2 ACTUAL YESA RESERVOIR

Figure 21: Arial picture of the Yesa reservoir

2.2.1 THE OPERATION OF THE YESA RESERVOIR FROM 1959 TO 2000

2.2.2 DATA QUALITY

Obliquely positioned water surface due to wind forces

Changing bathymetry due to sedimentation

2.3 YESA ENLARGEMENT PROJECT

2.3.1 SPANISH WATER POLICY

Figure 24: Estimated number of large dams worldwide

2.3.2 HISTORY OF THE PROJECT

2.3.3 VALUATION OF THE PROJECT

2.3.3.3 DISTRIBUTION OF THE ADDITIONAL WATER VOLUME

General supply of the Ebro basin

That there are surpluses in the source territory.

2.3.3.4 AUTHOR’S CONCLUSION ON THE ARGUMENTATION

2.4 MODEL OF THE YESA RESERVOIR

2.4.1 RUN-OFF SCENARIOS

2.4.2 MODELING OF THE ACTUAL RESERVOIR