Conservation of water in the agricultural sector
is essential since water is necessary for the growth of plants and crops. A
depleting water table and a rise in salinity due to overuse of chemical fertilizers
and pesticides has made matters serious. Various methods of water harvesting
and recharging have been and are being applied all over the world to tackle the
problem. In areas where rainfall is low and water is scarce, the local people
have used simple techniques that are suited to their region and reduce the
demand for water.
In India’s arid and semi-arid areas, the
‘tank’ system is traditionally the backbone of agricultural production. Tanks
are constructed either by bunding or by excavating the ground and collecting
rainwater.
Rajasthan, located in the Great Indian
Desert, receives hardly any rainfall, but people have adapted to the harsh
conditions by collecting whatever rain falls. Large bunds to create reservoirs
known as khadin, dams called johads, tanks, and other methods were applied to
check water flow and accumulate run-off. At the end of the monsoon season,
water from these structures was used to cultivate crops. Similar systems were
developed in other parts of the country. These are known by various local names
¾ jal talais in Uttar Pradesh, the haveli system in Madhya Pradesh, ahar in
Bihar, and so on.
Reducing water demand
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.
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.
Soil covered by crops, slows down run-off
and minimizes evaporation losses. Hence, fields should not be left bare for
long periods of time.
Ploughing helps to move the soil around.
As a consequence it retains more water thereby reducing evaporation.
Shelter belts of trees and bushes along
the edge of agricultural fields slow down the wind speed and reduce evaporation
and erosion.
Planting of trees, grass, and bushes
breaks the force of rain and helps rainwater penetrate the soil.
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.
Contour farming is adopted in hilly areas
and in lowland areas for paddy fields. Farmers recognize the efficiency of
contour-based systems for conserving soil and water.
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
freshwater sources. Thus, this is a good water conservation strategy.
Transfer of water from surplus areas to
deficit areas by inter-linking water systems through canals, etc.
Desalination technologies such as
distillation, electro-dialysis and reverse osmosis are available.
Use of efficient watering systems such as
drip irrigation and sprinklers will reduce the water consumption by plants.
