Simple techniques can be used to reduce the demand for water. The underlying principle is that only part of the rainfall or irrigation water is taken up by plants, the rest percolates into the deep groundwater, or is lost by evaporation from the surface. Therefore, by improving the efficiency of water use, and by reducing its loss due to evaporation, we can reduce water demand.
There are numerous methods to reduce such losses and to improve soil moisture. Some of them are listed below:
i. Mulching, i.e., the application of organic or inorganic material such as plant debris, compost, etc., slows down the surface run-off, improves the soil moisture, reduces evaporation losses and improves soil fertility.
ii. Soil covered by crops, slows down run-off and minimizes evaporation losses. Hence, fields should not be left bare for long periods of time.
iii. Ploughing helps to move the soil around. As a consequence it retains more water thereby reducing evaporation.
iv. Shelter belts of trees and bushes along the edge of agricultural fields slow down the wind speed and reduce evaporation and erosion.
v. Planting of trees, grass, and bushes breaks the force of rain and helps rainwater penetrate the soil.
vi. Fog and dew contain substantial amounts of water that can be used directly by adapted plant species. Artificial surfaces such as netting-surfaced traps or polyethylene sheets can be exposed to fog and dew. The resulting water can be used for crops.
vii. Contour farming is adopted in hilly areas and in lowland areas for paddy fields. Farmers recognise the efficiency of contour-based systems for conserving soil and water.
viii. Salt-resistant varieties of crops have also been developed recently. Because these grow in saline areas, overall agricultural productivity is increased without making additional demands on fresh water sources. Thus, this is a good water conservation strategy.
ix. Transfer of water from surplus areas to deficit areas by inter-linking water systems through canals, etc.
x. Desalination technologies such as distillation, electro-dialysis and reverse osmosis are available.
xi. Use of efficient watering systems such as drip irrigation and sprinklers will reduce the water consumption by plants.