Environmental hydraulics: integrated water management solutions from cloud to coast

Rivers 2011 6th – 9th December 2011, Penang, Malaysia Environmental Hydraulics: Integrated Water Management Solutions from Cloud to Coast ROGER A. FALCONER, Halcrow Professor of Water Management, Hydro-environmental Research Centre (HRC), Cardiff School of Engineering, Cardiff University, The Parade, Cardiff, CF24 3AA, United Kingdom. Email: falconerra@cardiff.ac.uk KUNLE AKANDE, Associate Director and Leading Specialist, Halcrow Group Ltd., Burderop Park, Swindon, Wiltshire, SN4 0QD, United Kingdom BRIAN A. BOYE, Research Student, Hydro-environmental Research Centre, Cardiff School of Engineering, Cardiff University, The Parade, Cardiff, CF24 3AA, United Kingdom ABSTRACT This paper reviews the traditional approach of linking models to cover integrated water management from the upper reaches of catchments through river basins, into estuaries and then into the marine environment. It highlights some of the deficiencies in the approaches currently being adopted in many of non-integrated studies, where artificial boundaries are included in the system and then highlights the need for a more integrated conceptual approach. Two example studies are discussed, namely the non-compliance of bathing waters along a UK coastal site from riverine inputs, with the inputs arising from agricultural and urban runoff, and the proposed Severn barrage project where a large barrage is proposed across the Severn estuary to provide 5% of the UK’s electricity needs. In this latter case study the barrage will have a major impact on the turbidity levels upstream, which will significantly impact on the levels of light penetration through the water column and potentially faecal indicator organisms. An integrated approach shows that the lower turbidity levels leads to improved water quality, through increased light penetration. Keywords: Environmental hydraulics, computational hydraulics, integrated water management, water quality, turbidity 1 river or in the estuary etc. as depicted in Figure 1. It is the modeller who creates the boundary and we need to ensure that such boundaries are as smooth and as transparent as possible. For example, it is imperative that when a 1-D model is linked to 2-D model there should not be a sudden change in the bed friction or the diffusion/dispersion values included in the integrated model, unless the sudden change can be justified. Thus the challenge is to have a truly integrated water management system for accurate and effective solutions and this paper seeks to develop appropriate solution methods for implementation of a Cloud to Coast C2C solutions approach. Introduction In the current environment where nations increasingly accept that climate change is happening and more countries are experiencing the impact of climate change, in the form of increased floods and more intense storms or more droughts etc., there is a growing interest worldwide in adopting a more integrated approach to river basin management, particularly when rivers cross state boundaries and countries. For example, within Europe there is the EU Water Framework Directive, wherein member states are required to set up river basin management plans. Integrated water management is not new; many research teams and companies have been modelling the system from the cloud to the coast for many years, but in many of these instances there have been different teams or individuals modelling and monitoring environmental hydraulics parameters through the catchment, river, estuary and coastal basin. However, all too often different parameters and formulations have been used in these studies for the various processes. When models are linked from catchments to rivers, and particularly rivers to estuaries and coastal basins, artificial boundaries are created in a natural system where, in general, no boundary exists in nature. When the raindrop falls from the cloud to the catchment, and moves from the stream to the river, to the estuary and to the sea, it does not know at any stage whether it is in the Figure 1 Water Cycle (Royal Academy of Engineering 2010) 4  3rd International Conference on Managing Rivers in the 21st Century: Sustainable Solutions for Global Crisis of Flooding, Pollution and Water Scarcity resilience and the associated economies of scope and scale. The C2C solutions approach embraces the findings of the US National Science Foundation report on revolutionising science and engineering through CyberInfrastructure” (see Atkins et.al., 2003), which identifies opportunities in integrated approaches linked to new developments in computing and communications technology. The purpose of this paper is to introduce an innovation in integrated water management for engineers and scientists with responsibility for water ecosystem and catchment and river basin management. Observation of movements and patterns between features in the water environment often suggest an underlying conceptual relationship. Within a C2C system, a component of a complex system is indeterminate until that component can be associated with other features of the system. The starting point for the application of the C2C solutions philosophy is the definition of the C2C boundary and its conceptualization in space and time, within the context of the C2C Decision Matrix shown in Figure 2. Within the defined C2C boundary, prediction of system behaviour, interaction between system components is achieved through the use of combined models facilitated by an OpenMI interface. Promotion of the C2C solutions concept to-date, has involved the development of a protocol for implementation, as a system based approach. The protocol generally involves Understanding integration requires an appreciation of systems. Systems thinking helps to understand the ‘big picture’ whilst still retaining the complexity of smaller systems. Considering a catchment (or other elements of the environment) as a system means taking account of multiple perspectives, stakes, purposes, boundaries, interdependencies, controversies and practices within it. Systems are best understood locally, however there is a risk that localism can threaten strategic priorities. Water sector needs, driven by climate variability, urbanisation and energy considerations, coupled with the challenges of investment planning, require innovative solutions. Halcrow and the HRC at Cardiff University in a strategic collaboration have developed such an innovative approach for integrated water management. This result, promoted as Cloud to Coast or C2C solutions, is described herein through two case studies. In the first study the HRC work started with a basic research of the C2C concept linking bathing water compliance of an estuarine basin. However, the requirements for practical application of the C2C approach are now being developed further through an on-going Halcrow supported Natural Environment Research Council funded collaboration with industry CASE research studentship. Although the term “C2C solutions” is new, as stated previously the concept of integrated water management is not new. There are three current Figure 2 Cloud to Coast Application Matrix a modelling component and a stakeholder participatory component, both dependent upon one another. An introductory case study used for the proof of the C2C concept, based on an investment planning project, is one of the conceptual examples being used as part of the on-going C2C proof of concept activities. The project is aimed at developing a sustainable water integrative approaches in the literature, each with different implementation problems. The approaches are: watershed or river basin management, adaptive management, and water resources management in the context of global environmental change. C2C solutions are aimed at developing water infrastructure and maintenance programmes that incorporate system 5  Rivers 2011 6th – 9th December 2011, Penang, Malaysia management strategy for a riverine special area of ecological conservation. In this application, whilst acknowledging that the C2C system is a continuum, the system was divided into two contrasting parts so that assessment and investments could be defined for the upper and lower parts of the system and for the system as a whole (see Figure 3). For the case study a comparison of the investment proposal with or without C2C solutions is given in Table 1. The river water highlighted in the above schematic is used for potable and non-potable water supplies. Two water treatment plants identified as WTW(1) and WTW(2) provide potable water. Wastewater collection and treatment is achieved through combined and separate sewer systems. The central wastewater treatment plant (WwTW) discharges treated flows to a depleted reach of the river, which is eutrophic with wildlife interests. Although the discharge of treated effluent upstream of WTW(2) provided a boost to the local water resource, it has also introduced a range of water quality problems. With the constraints of land space, the capacity of the storm tanks at the WwTW is inadequate under flooding conditions. Prior to the introduction of C2C solutions, the area marked A in the case study schematic was analysed. Without C2C solutions, the investment strategy called for additional and expensive treatment processes to be added to WTW (2), at a unit cost of 64p/m3, to address the water quality problems. With the introduction of C2C solutions, the boundary of the system was re-defined and conceptualised. Application of the C2C solutions approach resulted in the following: a) Development of control rules for upstream groundwater flow augmentation as a replacement water resource for WTW (2). b) Relocation of the WwTW outfall downstream of the raw water intake for WTW(2), with a large reduction in unit treatment costs at WTW(2) from 64p/m3 to 30p/m3. Lomborg (2007) in the publication titled “Solutions to the World’s Biggest Problems” stated that putting prices on such solutions make investment decisions better informed. This is one of the strengths of the innovative C2C solutions approach for the design and operation of water systems. The above example highlights that a C2C solutions concept is feasible. It ensures that the wider implications of interventions are understood for investment planning. New knowledge on when and where C2C solutions would be cost effective has been developed to increase visibility of risks. There are integrated benefits from the application of the C2C solutions philosophy for people and wildlife. Table 1 A comparison of aspects of Investment Proposal for the Case Study with or without C2C solutions Aspect 4 Approach to sustainable water management Control philosophy for operations Evaluation of climate change adaptation strategies Long term cost 5 Short term cost 1 2 3 With C2C Solutions Without C2C Solutions Holistic Reductionist Demand led (flexible) Yield led (rigid) Robust Weak Low Low to High depending on system complexity High Probably High 2 In applying the C2C approach to practical river and coastal basin studies, involving environmental and ecohydraulics problems, details are first given herein of the integrated modelling formulations used to simulate the hydrodynamic and solute transport processes in the river, estuarine and coastal system. The flow and solute inputs from the catchments are not included herein, but were provided from use of the field data and land-use management models as outlined later in the paper. The hydro-environmental models used by river and coastal basin engineers and environmental managers to predict the flow, water quality and sediment transport Figure 3 Conceptual basis of case study and flow profile 6  Integrated Modelling Details 3rd International Conference on Managing Rivers in the 21st Century: Sustainable Solutions for Global Crisis of Flooding, Pollution and Water Scarcity where Y = speed of earth’s rotation, I = earth’s latitude and g = gravitational acceleration. The main effects of the earth’s rotation, giving rise to the Coriolis acceleration, are to set up transverse water surface slopes across the river and to enhance the effect of secondary currents and meandering. For three-dimensional flow predictions, either the full three-dimensional governing equations are solved, which leads to a complex numerical formulation to evaluate the pressure P, or, more usually, a hydrostatic pressure distribution is assumed to occur in the vertical (z) direction, and leading to an expression for P of the following form: processes in river and coastal systems are based on first solving the governing hydrodynamic and solute transport equations. For a Cartesian co-ordinate system, with the main body of the flow in the x-direction, the corresponding 3-D Reynolds averaged equations for mass, momentum and solute in the flow direction can be written in a general conservative form as (Falconer and Lin, 1997): wu wv ww   wx wy wz wu wu 2 wuv wuw    wy wz wt wx , 1 (1) 0 X , 3 1 wP U wx P( z )  wu cu c wu cvc wucwc (2)   wx wy wz where u, v, w = velocity components in x, y, z co- wP wx wM wuM wvM wwM w w w     u cM c  vcM c  wcM c wt wx wy wz wx wy wz , 2 (3) 4 ordinate directions respectively, t = time, X = body force in x direction, U = fluid density, P = fluid pressure, u cu c , u cv c , u cw c = Reynolds (or apparent) stresses in the x direction on the x, y, z planes respectively. Similar equations to the momentum equation (2) can be written to evaluate the velocity components v and w in the y and z directions respectively. For the numbered terms in the momentum equation (2), these terms refer to: local acceleration (term 1), advective (or convective) acceleration(2), body force (3), pressure gradient (4) and turbulent shear stresses (5). Likewise for the solute transport equation (3) M = time averaged solute concentration, Ms = source or sink solute input (e.g. an outfall), Md = solute decay or growth term, and Mk = total kinetic transformation rate for solute, with the individual terms in equation generally referring to: local effects (term 1), transport by advection (2), turbulence effects (3), and source (or sink), decay (or growth) and kinetic transformation effects (4). In modelling estuarine flows in two and three dimensions then the effects of the earth’s rotation needs to be included giving, for the body force components: Y Z 2vY sin I ½ ° 2uY sin I ¾ ° g ¿ wH wP  Ug sin T  a wx wx ª wu wu º ½  u cu c Q t «  » ° ¬ wx wx ¼ ° ª wu wv º °°  u cvc Q t «  » ¾ ¬ wy wx ¼ ° ª wu ww º °  u cwc Q t «  »° ¬ wz wx ¼ °¿ (6) (7) where typically for a depth averaged flow the viscosity Q t can be estimated from field data of the vertical velocity profile or, assuming bed-generated turbulence dominates over free shear layer turbulence, then a logarithmic velocity profile can be assumed, together with field and laboratory data giving (Fischer et al., 1979): Q t 0.167U * H (8) where U* = shear velocity. For most practical riverine and coastal systems, even this value is low compared to measured data recorded in rivers, with values for Q t (U * H ) typically ranging from 0.42 to 1.61. For the bed friction, this term is also generally represented in the form of a quadratic friction law, as given by: (4) 7  Ug where T = angle of channel slope. Likewise, a similar representation can be written for the pressure gradient in the y direction. Apart from modelling flows in long rivers, the effects of the atmospheric pressure gradient are generally small and are neglected in the riverine part of the system. The only unknown terms remaining in equation (2) are the Reynolds stresses, which need to be related to the 3-D velocity field before solving for the water levels and the three-dimensional velocity components and are generally represented in a diffusive manner, giving: 3 Ms  Md  Mk X (5) where H = total depth of flow, z = elevation above the bed and Pa = atmospheric pressure. The corresponding derivative of equation (5), for inclusion in equation (2), gives: 5 1 Ug ( H  z )  Pa 4 2 Rivers 2011 6th – 9th December 2011, Penang, Malaysia (ii) Turbidity – important in governing the flow conditions and biological processes for many water quality constituents. (iii) Temperature – important in governing the flow conditions and biological processes for many water quality constituents. (iv) Other physical indicators – such as colour, conductivity and radio activity. Vs (9) C 2H where Vs = depth average fluid speed, qx = discharge per unit width in the x-direction, and C = de Chezy roughness coefficient, which can be expressed in terms of the Manning roughness formulation as: W xb C Ugq x H 1/ 6 n (10) 2. Chemical indicators of water quality: (i) Dissolved oxygen – which is important for water quality, since it is essential for supporting most forms of aquatic life. (ii) Biochemical oxygen demand – which is a measure of the consumption of bacteria during aerobic degredation of organic matter. (iii) Nitrogen – which is an essential nutrient for biological growth and a major constituent of domestic effluents. Nitrogen may be present in a variety of chemical forms, including: organic, ammoniacal, nitrite and nitrate nitrogen. (iv) Phosphorous – which is also an essential nutrient for biological growth and which appears exclusively as phosphate in aquatic environments. Phosphate may be present in several forms, including: orthophosphate, condensed phosphates (i.e. pyro-, meta- and poly-phosphates) and organically based phosphates. (v) Chlorides – commonly occurring in the form of salinity in estuarine reaches and an indication of sewage pollution in rivers. (vi) Metals – particularly those which are easily dissolved in water and are toxic, e.g. arsenic, cadmium, chromium, lead and mercury. These metals occur mainly as a result of industrial discharges, mine water tailings and agriculture. Although these contaminants are usually only present in low quantities, they can accumulate in the food chain and cause toxicity problems. where H = total depth of flow in a wide estuary or open coastal basin, or the hydraulic radius in a relatively narrow river and where side-wall effects are crucial and n = Manning roughness coefficient, with typical values of n being in the range from 0.012 for smooth lined channelised rivers to 0.04 or more for meandering rivers with vegetation etc. Although this approach is appropriate for most rivers, the Manning representation assumes that the flow is rough turbulent flow and that the local headloss is dependent only on the size and characteristics of the bed roughness, i.e. form drag dominates totally. However, for low velocity flows on shallow floodplains and wetlands, Reynolds number effects may be significant, reflecting the increased influence of skin friction. This complex hydrodynamic phenomenon can be represented using the more comprehensive friction formulation given by Colebrook-White (Henderson, 1966). For the solute transport equation The crossproduced terms u cMc etc. represent the mass flux of solute due to the turbulent fluctuations and, by analogy with Fick’s law of diffusion, it can be assumed that this flux is proportional to the mean concentration gradient and is in the direction of decreasing concentration. Hence, the terms can be written as: wM ½ ° wx ° wM ° vcM c  Dty ¾ wy ° wM ° wcM c  Dtz ° wz ¿ ucM c  Dtx 3. Biological indicators of water quality: (i) Pathogens – including the faecal coliform group, with the principal bacteria being Escherichia Coli. (ii) Other biological organisms – such as algae. (11) In modelling these various water quality indicator parameters in river and coastal basin systems, each process includes a range of different source terms and kinetic interactions. Details of these interactions are given in the US Environmental Protection Agency manual Bowie et.al. (1985). where Dtx, Dty, Dtz = turbulent diffusion coefficients in x, y, z directions. For riverine flows it is common to assume isotropic turbulence and to approximate the horizontal diffusion terms to the depth mean coefficients as given by Fischer (1973), whereby in the absence of field data, these terms are often equated to: Dtx Dty 0.15U * H 3 (12) 3.1 General In modelling water quality processes in rivers and coastal basins a range of indicator organisms are often modelled, including (Falconer and Chen, 1996): 1. Physical indicators of water quality: (i) Suspended solids – including inorganics, e.g. sand, and organics, e.g. sewage solids. The differential flow and water quality equations outlined above can be solved using a wide range of commercial or research orientated hydro-environmental software tools. The first author has been involved in 8  Integrated Model Applications 3rd International Conference on Managing Rivers in the 21st Century: Sustainable Solutions for Global Crisis of Flooding, Pollution and Water Scarcity the development of 3-D (TRIVAST), 2-D (DIVAST) and 1-D (FASTER) flow, water quality and sediment transport research based models and the details are given herein of the application of these models to flow in compound channels and, in particular, using a C2C approach to two recent studies in the UK, namely faecal indicator level predictions in the Ribble Estuary and sediment and bacteria levels in the Severn Estuary as a result of a barrage across the estuary to generate renewable energy. occasionally failed to comply with the EU mandatory water quality standards of the Bathing Framework Directive. A hydro-environmental modelling study was undertaken to establish the water quality of the EU designated bathing waters located at the mouth of the Ribble estuary. In order to reduce the possible inaccuracies caused by setting up the boundary conditions required by the numerical models, the upstream boundaries were set up at the tidal limits of the rivers Ribble, Darwen and Douglas (see Figure 4) and the downstream boundary was located around the 25 m depth contour in the Irish Sea. The length of the seaward boundary was 41.2 km, with the width of the river boundaries being generally less than 10 m. Such a great variation in the modelling dimensions made it impractical to use either a 1-D or a 2-D model alone. In applying either of these two models individually or linking the models statically would have introduced inaccuracies in the model prediction results and would also have required a considerable amount of effort in exchanging the data. Thus, in this study a 1-D and 2-D model (namely FASTER and DIVAST) were linked dynamically to create a single model, in which the numerical simulations of the hydrodynamic variables and bacterial indicators were undertaken simultaneously across the entire modelling region. More details regarding this linked model may be found in Kashefipour et al (2002). An extensive programme of data collection was also undertaken by the U.K. Environment Agency to provide data for model calibration and verification. Hydrodynamic and water quality data were collected at 6 sites during the winter period of 1998 and the summer period of 1999, to include a combination of different weather and tide conditions. During each survey measurements were taken at all discharge locations and upstream river boundaries (i.e. tidal limits) for two consecutive days. Comprehensive data sets were collected, including: water depths, current speed and directions, salinity levels and concentrations of suspended solids, faecal and total coliforms, and faecal streptococci. In total there were 34 input sources identified that contributed to the pollution loads of the estuary. These included: direct discharges of treated wastewater from treatment plants, inputs from the upstream boundary of the 3 major rivers, and inputs from several smaller rivers and combined sewer overflows. Four calibration points were chosen along the main channel of the Ribble, with these sites being referred to as: 11milepost, 7milepost, 3milepost and Bullnose (see Figure 4). Measurements at these locations were taken only for the second day of a survey. The 2-D area was represented horizontally using a mesh of 618 u 454 uniform grid squares, each with a length of 66.7m. A total of 1075 cross-sections was designed for the 1-D area with a minimum and maximum distances between two consecutive crosssections being 10m and 50m respectively. 3.2 Bathing Water Quality in the Ribble Basin The Ribble estuary is located along the north-west coast of England. At the mouth of the estuary there are two well known seaside resorts, namely Lytham St Annes and Southport, with both being designated EU (European Union) bathing waters. The Fylde Coast, which is bounded between Fleetwood in the north and the Ribble estuary in the south, includes one of the most famous beaches in England for tourism, namely Blackpool, with an average of more than 17 million visitors per annum. The area has four main centres of population, namely Blackpool and Lytham St Annes to the north of the Ribble Estuary, Southport to the south of the estuary, and the town of Preston, which is inland and straddles the river Ribble at the tidal limit (see Figure 4). BlackPool 433000 431000 429000 Fylde Coast St Anne’s North Preston Ribble Boundary Bullnose Lytham , St Annes St Anne’s Pier 427000 7milepost 11milepost Blue Bridge 3milepost Penwortham Darwen Boundary Upstream 2-D Boundary 425000 Downstream 1-D Boundary 423000 Measuring Water Elevation Tarleton Lock 421000 Tide Survey Point Measuring Discharge Douglas River 419000 Southport Southport Upstream 1-D Boundary Bathing Water Point 417000 415000 413000 Wanes Blades Bridge Douglas Boundary 411000 326000 330000 334000 338000 342000 346000 350000 354000 358000 362000 Figure 4 Fylde Coast, showing the Ribble Estuary and its Tributaries In order to enhance the bathing water quality along the Fylde coast, a major civil engineering investment programme was undertaken in recent years to reduce the bacterial input to the estuary. About £600 million was invested over the past 20 years in new sewerage works and treatment plants along the Fylde Coast and Ribble Estuary. Examples include:- upgrading the wastewater treatment works at Clifton Marsh from primary treatment to include UV disinfection; reducing storm water discharges from the wastewater network by constructing 260,000 m3 of additional storage. Although the reduction in input bacterial loads has resulted in a marked decrease in the concentration of bacterial indicators in the coastal receiving waters, occasional elevated faecal coliform counts were still measured. As a result, the bathing waters still 9  Rivers 2011 6th – 9th December 2011, Penang, Malaysia June 1999 were compared in Figure 6, using the original model. Due to the large variation in the values of faecal coliform concentrations, the results are plotted using a logarithmic scale. Relatively good agreement between both sets of data were obtained from this figure, with an average error of 35000cfu/100ml, i.e. 30.5%. Figure 7 shows an example of application of the original linked model application to the Ribble estuary, comparing the predicted and measured faecal coliform concentrations at 3milepost for the 19th May 1999 survey, which was carried out for a dry event and a spring tidal range. As can be seen from this figure both sets of data agreed well, with an average error of 477cfu/100ml, i.e. 27.6%. For this dry event the T90 Measured discharges at the upstream tidal limits of the rivers Ribble, Darwen and Douglas were used as the upstream open boundary conditions. The water levels for the seaward boundary conditions were acquired from the Proudman Oceanographic Laboratory (POL), predicted using their Irish Sea model. The main parameter used for calibration of the hydrodynamic model was the bed roughness. By changing the values of the bed roughness and comparing the model predictions with measured data, the model was calibrated by choosing the best fit between the predicted results and measured data. Different roughness values were used along different reaches of the model domain to reflect the local conditions. For the open coastal waters it was found that the most appropriate value for the Nikuradse equivalent sand grain roughness was 20 mm. For the 1-D model region the Manning roughness coefficient was used, with the optimum values ranging from 0.021 for the lower part of the river to 0.028 for the upper part of the river. M ode l 7mile p o st be 20.8hrs. All of these values were for a water temperature of 20qC. Wate r Ele v atio n M e asu r e d 4 2 0 (a) 1.0E+07 Concentration (cfu/100ml) Elevation (m ) 6 values for the 2-D area were found to be 14.7 and 20.2hrs for day- and night-time periods respectively. The corresponding values for the 1-D area were obtained and found to be 21.4 and 26.9hrs respectively. For this event an average T90 value was considered to -2 3 Cu r r e n t Sp e e d Speed (m/s) 2.5 2 1.5 1 Model Measured Faecal Coliform at 7milepost 03/06/1999 1.0E+06 1.0E+05 1.0E+04 1.0E+03 1.0E+02 1.0E+01 0.5 (b) 0 1.0E+00 30 32 34 36 38 40 42 44 Simulation time (hr) 46 48 50 -0.5 Figure 6 Comparison of predicted and measured faecal coliform concentrations at 7milepost, on 3 June 1999 C urrent D irection 400 300 1.0E+06 200 100 Concentration (cfu/100ml) Direction (deg) 500 (c) 0 30 32 34 36 38 40 42 44 46 48 50 S im u la tion tim e (hr) Figure 5 Comparison of predicted and measured: (a) water levels, (b) current speeds and (c) current directions at 7milepost, on 3 June 1999. Measured 1.0E+04 1.0E+03 1.0E+02 1.0E+01 1.0E+00 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 Simulation time (hr) Figure 7 Comparison of predicted and measured faecal coliform concentrations at 3 milepost, on 19 May 1999 As an example of the simulations for the original study are given herein where the results obtained for the survey on the 3rd June 1999 are discussed (Kashefipour et.al. 2002). This survey was carried out during a wet period with a mean tidal range. Figures 5a to 5c show comparisons at 7milepost between the predicted water elevations and current speeds and directions respectively. Figure 5a shows that good agreement was achieved between the predicted and measured water levels at this site, with an average error of 0.11m, i.e. 2.1% error, when compared with the measured tidal range. Figures 5b and 5c illustrate relatively good agreement between the predicted current speeds and directions with the corresponding measured data, with an average error of 0.13m/s (i.e. 8.8% error relative to the maximum measured speed) and 8.1q respectively. Predicted and measured faecal coliform concentrations at 7milepost for the survey on the 3rd In reviewing the original study, directed by the first author (Kashefipour et.al., 2002), in the context of a C2C solutions approach, the authors found a number of anomalies with the original study and some key lessons learnt for the future, particularly in the context of the principle that the raindrop – possible with attached pollution (either in solution or in particulate form) does not know whether it is in a catchment stream, river, estuary or coastal basin. Taking account of these anomalies the following observations were recently made with regard to the original studies: (i) different values of the decay rate were used in the 1-D and 2-D parts of the linked model (see Table 2), with the decay rate being higher in the 2-D part of the 2-D part of the linked model in comparison with the 1-D part. The length of day-time was assumed to be 12hr from sunset to sunrise; 10  Model Faecal Coliform at 3milepost 19/05/1999 1.0E+05 3rd International Conference on Managing Rivers in the 21st Century: Sustainable Solutions for Global Crisis of Flooding, Pollution and Water Scarcity (ii) (iii) model was nearly two orders of magnitude greater than that in the 1-D model at the same site. A similar comparison again showed that the peak concentration was not reached quite so closely as for the old model but that the lower values were much more closely predicted when an integrated C2C approach was adopted and a unified value of 100 was used for the dispersion constant J in the dispersion equation. different values of the dispersion coefficient were used in the 1-D and 2-D parts of the linked model (see Table 3); different values and formulations were used for the roughness coefficient in the 1-D (Ks=20mm) and 2D (n=0.021) linked models. Table 2 Differences in Decay Rate for 1-D and 2-D Model Domains Faecal Coliform Decay Rates 1-D 2-D Day time Decay Rate (per day) 0.85 1.0 Equivalent Day time t90 value(hr) 65.0 55.3 Night Time Decay Rate (per day) 0.5 0.68 110.5 81.3 Equivalent Night Time t90 value (hr) Table 3 Differences in Dispersion cCoefficients for 1-D and 2-D Model Domains Location Original Model Milepost 7 (m2/s) 1.44 m2/s Milepost 11 (m2/s) 1.63 m2/s Node 1 (m2/s) 256 m2/s Node 51 (m2/s) 240 m2/s Figure 8 Comparison of Faecal Coliform Levels with Time for the New and Old Models after Changes in Decay Rates In adopting a C2C solutions approach to this study site, the integrated catchment to coast model was re-run using the same formulations for the momentum correction coefficient, eddy diffusivity, Manning roughness coefficient, dispersion and diffusion coefficients and the kinetic decay rates (specified in the form of T90 values) along the whole river and coastal basin and with the various parameters only being changed where there were sound technical reasons for doing so. This differed from the previous study where the value of the parameter was very much based on whether the ‘water package’ was in the 1-D, 2-D or 3-D model domains. In the new model, the T90 value was set as 20hr for day time and 100hr for night time in both the 2-D and 1-D models. The equivalent daytime rate (2.76 per day) was therefore higher than the values in the old model (Kashefipour et.al., 2002). The equivalent night time decay rate (0.55 per day) is lower than that in the 2-D part of the previous model. A comparison of the resulting faecal coliform predictions is shown in Figure 8, both for the old and new models, with these values for the day and night time decay rates being found to give closest agreement with the field data. The results of this comparison show that whilst the old model, which was calibrated to a maximum in each reach, gave best agreement with the peak faecal coliform results, there is no doubt that the lower levels were much more accurately predicted using the more holistic systems based C2C solutions approach and hence provides a more accurate tool for decision planning for the future. Likewise similar results were obtained for the dispersion and diffusion coefficients, where in the old modelling study the dispersion coefficient in the 2-D Finally the resulting predictions for the faecal coliform concentration distributions are shown in figure 9 for the estuary using the old and new models, where a comparison of the C2C approach to modelling highlights the different concentrations predicted and the corresponding implications for investment strategies appropriate for the various treatment options and solutions in the river basin upstream. 3.3 Severn Tidal Power Water Quality Studies In recent years there has been growing international public concern about climate change, global warming, reducing the carbon footprint, increasing oil and gas prices and the rapid depletion of fossil fuel reserves. In addition to these challenges there is a growing global demand for energy. The UK is also committed to the EU renewable energy targets, with the UK being expected to produce 15% of its total energy from renewable resources by 2020, which corresponds to about 35% of the UK’s electricity demand. At present only about 5% of the UK’s electricity comes from renewable resources. More recently, the UK Committee on Climate Change recommended in October 2008 that the UK should aim to reduce greenhouse gas emissions by at least 80% by 2050 compared to 1990 levels. In the same timeframe, global emissions will need to fall by at least 50%. These issues, among others, have led to enthusiasm in the UK to look to increasing its generation of renewable energy from tidal sources, with tides having the advantage over wind and waves in that they are predictable. 11  Rivers 2011 6th – 9th December 2011, Penang, Malaysia because of its unique characteristics, the estuary is protected under a number of European and international legislative directives. The most attractive means of harnessing the tidal power from the Severn Estuary is therefore to build a barrage across the estuary. The UK Government has investigated this option and the most favourable alternative is the so called ‘Severn Barrage’. This barrage would span from Lavernock Point just south west of Cardiff, to Brean Down just south of Westonsuper-Mare (see Figure 10). (a) Old model Figure 10 Location of Severn Barrage (picture courtesy of Severn Tidal Power Group) (b) New model Figure 9 Simulations of Faecal Coliform in Ribble Estuary using (a) Old and (b) New (C2C) Approach to linked Modelling The traditional proposal for operating the barrage has been for the structure to be operated under ebb tide generation conditions only, wherein the sluice gates would be opened on the incoming tide and the turbines closed. The impounded area, of approximately 500km2, would be allowed to flood to high tide elevation, at which point during the tidal cycle the turbines and sluice gates would be closed. The impounded water would then be held for just over 2.5h to create sufficient head for generation, with the turbines then being opened and generating power over the next 5h. The main effects of the barrage would be to reduce the peak upstream tidal range from 14m to 7m. This would result in a significant loss of the intertidal habit areas, estimated to be a loss of 14,000h. The currents would reduce significantly upstream of the barrage, leading to reduced levels of suspended sediments and turbidity. There would be an increase in light penetration through the water column and an increase and change in the primary productivity of the benthic flora and fauna. The current and alternative proposals for the Severn Barrage have been studied extensively using hydro-environmental models, developed within the HRC at Cardiff University, to predict the hydrodynamic, sediment transport and water quality processes in the In considering the development of tidal renewable energy in the UK then the Severn Estuary and Bristol Channel is an ideal site. The estuary, including the Bristol Channel, is located some 240km (or 150miles) west of London and spans the South Wales coast from Milford Haven to Gloucester and the northern reach of the South West coast of England from Hartland Point, also to Gloucester. There is a weir at Gloucester and for most of the spring-neap cycle this defines the tidal limit of the estuary. The estuary, including the Bristol Channel, is approximately 200km long and has the second highest rise and fall of tide in the world, with typical spring and neap tidal ranges peaking at over 14m and 7m respectively at Avonmouth, which is just further upstream of the Port of Bristol. The spring tidal currents in the estuary are well in excess of 2m/s and there is a large area of intertidal mudflats. Suspended sediment levels are large, with the spring and neap loads being estimated at 30 Mt and 4Mt respectively. Light penetration through the water column is very limited and dissolved oxygen saturation levels are reduced. The estuarine regime is harsh and there is limited aquatic life in the water column. However, 12  3rd International Conference on Managing Rivers in the 21st Century: Sustainable Solutions for Global Crisis of Flooding, Pollution and Water Scarcity wastewater treatment works along the estuary and river (Environment Agency, 2007). Typical comparisons between measured and predicted water elevations and current speeds are given in Yang et.al. (2008), where good agreement has been obtained both sets of results. In particular, the results have been improved further following a C2C approach in terms of enhanced integration of the 1-D/2-D linking of the models. The model was then extended to refine the prediction of bacteria in coastal waters as part of an extensive research programme of field monitoring and numerical modelling to predict faecal contamination in the Bristol Channel and Severn Estuary where, despite extensive levels of wastewater treatment (including UV disinfection), high levels of enteric bacterial contamination were still found in some of the bathing waters along the estuary. In this study a new enteric bacterial–sediment transport interaction conceptual model was developed and measured data used to estimate the adsorption and desorption rates between the bacteria and the sediments. The data acquired through the field data monitoring studies showed that the bacteria can remain trapped within the sediments for considerably long periods, only to be released and transported potentially to bathing waters during storm or spring tide conditions. When the bacteria were adsorbed onto the sediments and deposited on the bed then the decay rate was found to be very low and the bacteria were regarded as almost conservative. Relatively good agreement was obtained between the measured and predicted levels of faecal coliform along the estuary, with the results highlighting considerable differences between the concentration levels measured and predicted when the interactions between the bacteria and the sediments were included in the model, see Gao et.al. (2011). Typical model predictions of bacterial levels in the estuary both with and without the barrage are shown in Figure 11. estuary, both without and with a barrage. The models used were similar to those used for the Ribble study and included both a 1-D/2-D linked regular grid model and an unstructured grid model, with the models being verified with field data and more recently tested against a small scale 1:25,000 physical model of the estuary. As part of the studies to refine the bacteriological model predictions for the estuary, experiments were undertaken from field data of faecal coliform levels to determine the T90 decay rate as a function of the suspended sediment levels and with another set of experiments being undertaken to establish the adsorption rates for the coliform levels on the sediments. The 2-D DIVAST and 1-D FASTER models were modified and set up to investigate the far-field impacts of the proposed barrage in the Bristol Channel and the Severn Estuary. Modelling studies were undertaken with the boundaries set from Milford Haven and Hartland Head along the western boundary and to Gloucester at the eastern extremity (Lin and Falconer, 1995). At Gloucester a flow rate varying between 60m3/s to 106m3/s was used for normal operating conditions. The 1-D model consisted of four reaches which were modelled using 351 cross-sections with an average distance of 240m between two consecutive cross-sections. The inflows for the four major rivers in the modelled area, namely the rivers Wye, Usk, Frome and Little Avon, were treated as lateral inflows. The 1D boundary was specified as a water level boundary and located close to the Severn Bridge, where water level data were used to drive the model, obtained from the 2-D model. To ensure stability in data transfer between the 1-D and 2-D models, and to ensure momentum conservation, the 1-D and 2-D models overlapped for a reach of over 4.5km between the old and new Severn Bridge crossings (Yang et al, 2008). In addition to flow and water elevation data being included at the open boundaries, discharges and enterococci inputs were included for all the main rivers and (a) (b) Figure 11 Predicted Coliform Levels in the Severn Estuary and Bristol Channel (a) Without and (b) With a Severn Barrage 13  Rivers 2011 6th – 9th December 2011, Penang, Malaysia agreement with the field data was obtained across a wider range of spatial and temporal measured data values, although the peak values were slightly under predicted. These model results could then be better used to give more informed and improved management decisions for more effective investment strategies for improved water quality in the river and coastal basin for the future. Finally, the authors are extending their C2C numerical modelling studies of the hydrodynamic, morphological, water quality and contaminant transport processes to the Severn estuary to predict the impacts of a proposed barrage across the estuary, for tidal energy provision, on the hydro-environmental characteristics of the basin. There is no doubt that such a barrage will have an adverse impact on a range of environmental and ecological aspects, and particularly upstream of the barrage, the model studies undertaken have shown that there will also be some positive hydro-environmental benefits associated with a barrage. In particular, there will be a general reduction in the magnitude of the tidal currents, leading to a significant reduction in the suspended sediment concentrations and turbidity levels. There will be a corresponding increase in the light penetration levels and reduced bacterial levels in the water column, due to the reduced input from bacteria adsorbed onto the sediments and the increased decay rate as a result of increased light penetration. The model predictions also show that there will be reduced peak water elevations, both upstream and downstream of the barrage, with the level upstream reducing by up to nearly 2 m at Gloucester. Using the C2C Solutions approach Halcrow and the HRC are currently investigating a range of options for this project, including two-way generation and low head turbine alternatives. In summarising the results from this study, including a C2C solutions approach, the key findings were as follows: (i) the peak high tide levels upstream of the barrage were approximately 1 m lower with a barrage and the high tide levels reduced typically of the order of 50 cm for a region up to about 15 km seawards of the barrage; (ii) the peak tidal currents exceeding 2 m/s were mainly in the main channel from a transect just seawards of Minehead to Aberthaw, to a transect upstream of the old Severn Bridge; (iii) the region upstream of the barrage is a region of high turbidity and high suspended sediment concentrations in excess of 1200mg/l, comparisons showed that if a barrage were built then the suspended sediment concentrations would be reduced significantly to about 200 mg/l, leading to increased light penetration in the water column and more rapid decay of enteric bacteria; (iv) the novel bacteria model showed that there was a strong interaction between adsorption and desorption of enteric bacteria with sediments, and particularly those sediments known to be high in organic content, with the resulting predictions showing that a barrage would lead to reduced bacterial levels in the water column in the region; and (v) the predictions of the peak water elevations have shown that the risk of flooding would be reduced both upstream and downstream if a barrage were built. 4 Conclusions The authors have introduced the concept of a systems based solutions approach to integrated water management in the form of Cloud to Coast C2C Solutions. The approach involves considering the water system in its entirety, rather than the current common practise of de-compartmentalising the basin into a catchment, river, estuary and coastal basin and treating each separately. Halcrow are currently applying a C2C approach to water projects and this approach is leading to improved and/or more efficient design solutions. In the context of modelling for C2C solutions, it is necessary to consider the raindrop as a water package, possibly with pollution, moving through the system (i.e. the catchment, river, estuary and coast), with the roughness, turbulence, diffusion, dispersion, decay etc, only changing if physically and/or bio-chemically appropriate and not based on the artificial boundaries imposed through modelling. In applying a C2C Solutions approach to hydroenvironmental modelling the authors have repeated a previous study (previously undertaken by the first author) using this concept, namely modelling the hydrodynamic and faecal indicator organism processes in the Ribble river and coastal basin in northern England. When applying the C2C approach the authors found inherent big changes in the roughness, dispersion and, to a lesser extent, the decay rates when transferring from the 1-D to the 2-D model in the original study. When removing these changes and re-calibrating the integrated linked models for unified parameters, better References 1. 2. 3. 4. 5. 14  The Royal Academy of Engineering (2010). Global Water Security: An Engineering Perspective. Published on line at www.raeng.org.uk/. Atkins, D.E., Droegemeir, K.K., Fieldman, S.I., Garcia-Molina, H., Klein, M.L., Messerschmitt, D.G., Messina, P., Ostriker, J. P. and Wright, M.H. (2003). Revolutionising Science and Engineering through CyberInfrastructure: Report of the National Science Foundation Blue-Ribbon Advisory Panel on CyberInfrastructure. Lomborg, B. (2007). Solutions for the World’s Biggest Problems. Costs and Benefits. ISBN-10 0511-36423-7. Cambridge University Press. Falconer, R. A. and Lin, B. (1997). Threedimensional modelling of water quality in the Humber Estuary. Water Research. 31(5), 10921102. Fischer, H.B., List, E.J., Koh, R.C.J., Imberger, J. and Brooks, N.H. (1979). Mixing in inland coastal waters. Academic Press Inc., San Diego, 483 pp. 3rd International Conference on Managing Rivers in the 21st Century: Sustainable Solutions for Global Crisis of Flooding, Pollution and Water Scarcity 6. 7. 8. 9. 10. 11. Lin, B. and Falconer, R. A., (1995). Modelling sediment fluxes in estuarine waters using a curvilinear co-ordinate grid system, Estuarine, Coastal and Shelf Science, 41(4), 413-428. 12. Yang, L., Lin, B. and Falconer, R. A. (2008). Modelling enteric bacteria levels in coastal and estuarine waters, Proceedings of Institution of Civil Engineers, Engineering and Computational Mechanics, 161(4), 179-186. 13. Environment Agency. (2007). Fate and transport of particles in estuaries, Vol. II: Estimation of enterococci inputs to the Severn Estuary from point and diffuse sources, Science Report SC000002/SR2, Environment Agency, 55pp. 14. Gao, G., Falconer, R. A. and Lin B. (2011) .Numerical modelling of sediment-bacteria interaction processes in surface waters. Water Research. 45(5), 1951-1960. Henderson, F.M. (1966). Open Channel Flow. Collier-Macmillan Publishers, London, 522 pp. Fischer, H.B. (1973) Longitudinal dispersion and turbulent mixing in open channel flow. Annual Review of Fluid Mechanics, Vol. 5, 59-78. Falconer, R.A. and Chen, Y. (1996). Modelling sediment transport and water quality processes on tidal floodplains. In: Floodplain Processes, M.G. Anderson, D.E. Walling and P.D.Bates (eds), John Wiley and Sons Ltd., Chichester, Chapter 11, 361398. Bowie, G.L. et al (1985). Rates, Constants and Kinetics Formulations in Water Quality Modelling, Environmental Research Laboratory, US EPA, Athens, GA, Report No. EPA/600/3-85/040, 475 pp. Kashefipour, S.M., Lin, B., Harris, E.L. and Falconer, R.A. (2002). Hydro-environmental modelling for bathing water compliance of an estuarine basin., Water Research, IWA, Vol. 36, pp.1854-1868. 15  View publication stats