AGE23 Lesson 2 LContent
AGE23 Lesson 2 LContent
AGE23 Lesson 2 LContent
Lesson 2
Drainage, objectives of drainage, familiarization
with the drainage problems of the state
CONTENT
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Drainage Engineering
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Drainage Engineering
Objective
i) to get well aquatints with basic of drainage, objectives of drainage and state
problem.
Irrigation and drainage constitutes a subset of water resources system and are
crucial for human survival Land drainage, or the combination of irrigation and
land drainage, is one of the most important input factors to maintain or improve
agricultural productivity.
To enlarge the present cultivated area, more land must be reclaimed than the
land that is lost due to urban/industrial development, roads and land
degradation. However, in some areas, land is a limiting resource, whereas in
other areas, agriculture cannot expand at the cost of nature.
Since drainage (land drainage) is necessary not only for the removal of excess
surface water or groundwater but also for removing salts from the soil, a precise
definition of drainage has been given by the constitution of the International
Commission on Irrigation and Drainage (ICID, 1979). According to ICID (1979),
land drainage is defined as follows:
“Land drainage is the removal of excess surface and subsurface water from the
land to enhance crop growth, including the removal of soluble salts from the
soil”.
The above definition of land drainage (or drainage) is well known and is used
worldwide.
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Drainage Engineering
for proper growth and yield of most food crops. Excess water and/or high salt
concentration in the root zone or at the land surface do not allow the plant roots
to function normally. As a result, the plant growth and yield are adversely
affected. In the extreme cases of water logging and salinity, the seeds may not
germinate and the plants may wilt permanently. The result is a loss of
agricultural production. Land drainage, as a tool to manage excess surface water
and groundwater levels, plays an important role in maintaining and improving
crop yields:
Drainage is the only way to reclaim the land which is not cultivated due
to waterlogging and salinity problems.
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Drainage Engineering
Waterlogging and salinity of agricultural lands are caused due to natural causes
or artificial causes (i.e., human interventions). Important natural causes are high
rainfall during the rainy season, unfavorable topography, backwater entry from
rivers, seawater intrusion, high evaporation during long dry periods, and the
salts present in the soil. On the contrary, important human factors are
unscientific management of land and irrigation water, use of poor-quality water
for irrigation, adoption of unscientific and non-sustainable cropping pattern,
and obstruction of natural outlets because of urbanization and construction of
highways and railways.
Table 1.1. Geographical, waterlogged and salt affected areas of some states
in India (Bhattacharya and Michael, 2003)
Madhya
7 44.20 0.057 0.242
Pradesh
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Drainage Engineering
The progress of the net sown area and its break-up into unirrigated and irrigated
areas in India is shown in Fig. 1.5 (FAI, 1998). Although the unirrigated area has
decreased with increasing irrigation development, about 80 M ha of the cropped
land is still unirrigated (rainfed). As the pace of irrigation development has
slowed down in recent years, much of the cultivated area may remain
unirrigated in the future. Thus, it is irrigation rather than drainage which should
be of concern for rained areas. However, due to the diversity of climate and soil,
even rainfed areas experience excess water during monsoon season and excess
salts during dry season (non-monsoon season). For example, land inundation
during the monsoon season and high soil salinity during the dry season prevent
cultivation in the coastal areas of Medinipur District, West Bengal. Vast flat lands
in southwestern Haryana and south-western Punjab, despite a low annual
rainfall, get waterlogged due to sudden rains and lack of drainage to clear out
the runoff fast. Lands in the plains of Bihar and Uttar Pradesh (U.P.) are
uncultivable during monsoon due to excess water. Thus, drainage is relevant
even in the unirrigated areas to ensure crop production.
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Drainage Engineering
Fig. 1.5. Progressive development of net sown, irrigated and rainfed areas in
India during 1950-2000 (the last values are extrapolated).(Source: FAI, 1998)
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Drainage Engineering
because of the fact that while land and the water resources are limited in
quantity and degradable, human population is gradually increasing in most Asian
and African countries. This necessitates more agricultural productivity per unit
of land and water, which will be possible only if further deterioration of land and
water resources is avoided or minimized, degraded lands are reclaimed and
these two vital resources are utilized judiciously.
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Drainage Engineering
References
Bower, B.T. and Husfschmidt, M.M. (1984). A conceptual framework fro analysis
of water resources management in Asia. Natural Resources Forum, 8(1): 343-
356.
FAI (1998). Fertilizer Statistics. The Fertilizer Association of India (FAI), New
Delhi, India.
FAO (1973). Drainage of Salty Soils. FAO Irrigation and Drainage Paper 16, Food
and Agriculture Organization of the United Nations, Rome.
Schwab, G.O., Fangmeier, D.D., Elliot, W.J. and Frevert, R.K. (2005). Soil and
Water Conservation Engineering. Fourth Edition, John Wiley and Sons (Asia) Pte.
Ltd., Singap
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Drainage Engineering