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<Sourcebook of Alternative Technologies for Freshwater Augumentation
in Some Countries in Asia>

5.2 India

The National Water Policy of India states that water is a prime natural resource, a basic human need and a precious national asset. It recommends that water resources planning be done for hydrological units, such as drainage basins or sub-basins. As far as possible, the projects should be planned and developed as multipurpose projects. Provision for drinking water should be given priority over other uses of water. The integrated and coordinated development of surface and ground waters and their conjunctive use should form an essential part of all water resources development projects, with recycling and re-use of water being an integral part of water resources development. Emphasis is placed on the preservation of the quality of the environment and ecological balance in planning, development and operation of water resources projects. The National Water Policy stresses the use of freshwater augmentation technologies as one means of alleviating India's chronic water shortages.

Water conservation may be achieved by modification of technologies and industrial processes in order to reduce the rate of water consumption. Better maintenance, interception and recovery of process water, and recycling can significantly contribute to water conservation efforts. Use of water of lesser quality, such as reclaimed wastewater, for cooling and as fire water can be an attractive option for large and complex industries to reduce their water costs, increase production and decrease the consumption of energy. This conserves better quality waters for potable uses. These technologies can be further complimented dew water harvesting or by constructing "dew ponds". The climatic conditions of some parts of Assam in Brahmaputra Valley and in hill areas hold promise for use of dew ponds. Public information programmes also contribute to water conservation in urban areas.

Agricultural water sources can be supplemented by small structures (pick ups) built across seasonal or perennial streams to check the flow of water at appropriate locations by constructing bunds using locally available materials like stones, boulders or even mud bunds turfed with a grass locally available (Maane hullu). Use of these structures results in water storage, groundwater recharge, prevention of soil erosion, and availability of water for other activities in areas where water would typically not be available for much of the year. In contrast, in the Krishna Delta, large demands for water from the Nagarjuna Sagar Reservoir have reduced the volume of freshwater reaching the Delta, and it has become necessary to utilize the groundwater supplies. In order to achieve an acceptable quality, however, groundwater must be used conjunctively with the limited surface water resources in a mix of 28:72, groundwater:surface water. Blending these waters should result in the conservation of storage in the reservoir of about 751 Mm3 for the first stage and 1 016 Mm3 for final stage, for a year with average inflows. In a more general sense, technological developments in the pumping methods and well construction have resulted in large-scale exploitation of groundwater throughout India which exceed the natural rate of replenishment of these resources. Thus, replenishment of the groundwater reservoirs by artificial recharge is essential.

TABLE 3. Water Evaporation Retardation (WER) Projects

Table 3

In many parts of the country, which have to face the vagaries of the monsoon, dependance on groundwater has increased tremendously, particularly in those areas where surface water resources are either lacking or inadequate, and storage of surface water is uneconomical because of high evaporative losses. Water loss due to evaporation has led to serious problems including acute shortages of drinking water for human consumption in some parts of India. Considering the huge loss of precious water, use of Water Evaporation Retardants (WER) on open surfaces of lakes and reservoirs is now being promoted by various State Governments and Local Authorities. Various substances capable of forming mono-molecular layers on a water surface have been investigated, and fatty alcohols in their pure form were found to be most suitable and effective in retarding evaporation with no known side effects. Water savings resulting from the prevention of evaporative losses using cetyl and stearyl alcohol have been reported to be as high as 50%, but are generally between 20% and 40%. Table 3 shows a list of projects where the evaporation retardants have been used. In India, rainfall is confined to about four months in a year and is inconsistent both in space and time, causing severe drought. In this context, whatever the source water used, irrigation is a must for agriculture in the country. However, there is an urgent need for efficient use of present available water so as to irrigate the maximum possible gross cropped area.

In India, sprinkler irrigation is being adopted in hilly terrains, for irrigation of many plantation crops. The use of sprinkler systems, which mimic natural rainfalls, was introduced in the State of Hariyana in 1970, and other states like Rajasthan, Uttar Pradesh, Karnataka, Gujarat, Maharashtra have since implemented sprinkler irrigation systems. In the State of Hariyana, it has been found that, the use of sprinkler irrigation has saved about 56% of water for the winter crops of Bajra and Jawar, while for cotton it has saved 29% as compared to the traditional gravity irrigation. Drip irrigation systems, a variation on piped irrigation that delivers water directly to the root zone of the crops, are of very recent origin, and are used on a limited scale in Tamil Nadu, Karnataka, Kerala and Maharashtra mainly for irrigation of coconuts, coffee, grapes and vegetables. Experimental studies on sugarcanes, banana and other fruits have shown a very high profitability in addition to water conservation.

TABLE 4. Water Loss Under Various Irrigation Methods.

Temperate Climate Hot Climate
Surface Irrigation 30 - 45% 35 - 50%
Gate pipe Irrigation 15 - 20% 20 - 25%
Sprinkler Irrigation 6 - 9% 10 - 20%

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