Prof (Dr) R.D. Gupta
Confronted with a grim prospect of an acute shortage of water both for drinking purpose and irrigating the crops, a number of experts have recommended for making rainwater harvesting and recycling of water mandatory. it is because arid and semiarid areas of the country experience with scarce and uncertain rainfall during monsoon. This as a result produces low, unstable and often uneconomical yields of various crops. Moreover, these lands owing to poor management practices are subjected to the process of degradation and as such these are unable to sustain the yield of arable crops particularly during drought years. Sometimes especially during severe drought, the yields of crops of such areas is so low that the farmers even can not get the cost of inputs they have used for cultivating these crops.
Thus, in light of the facts as stated above, rainwater harvesting which is a proven technology, must be utilized with letter and spirit for using its water for drinking purpose and irrigating the crops to increase food security in drought prone areas. Soil erosion control and recharge of ground water are the additional advantages of water harvesting technology. Adoption of rain water harvesting technology can be proved beneficial to the rainfed agriculture which extends over 85 million ha and constitutes about 60 per cent of the net cultivated area of the country.
A brief history of rainwater harvesting
Rainwater harvesting is an age old practice in India which traces its history in Biblical time. Rain water harvesting methods are known to exist more than 4,000 years ago in Palestine and Greece. In ancient Rome, residents were known to build with individual cisterns rainwater to angment water from city’s aqueducts. In the third millennium BC, farming communities in Baluchistan and Katch harvested rainwater, and used it for irrigation dams. In India during Indus Valley civilization most of the farmers used to irrigate their crops from the water of tanks which had already been filled with water after rain water harvesting technology.
What is meant by rain water harvesting?
Water harvesting means capturing of water usually from rains where it falls or it is the process of collection of runoff from treated or untreated land surfaces or catchments and taking all measures to keep that water clean by not allowing pollution to take place in the catchments. This happens naturally in open rural areas but in conjested over paved cities, we require to create methods to capture rainwater free from water pollution.
Rain water can also be harvested from roof tops and can be stored it in an open farm pond or closed water tanks, reservoirs or in situmoisture storage in the soil itself. Initially, an attempt should be rendered to retain as much water as could be stored in the soil where it falls, so as to provide a favourable moisture regime to the growing crops in rainfed areas. The excess rainwater that exceeds the infiltration and storage capacity of soil can be harvested nearby in the same field or at another convenient site in the watershed. In medium to high rainfall areas inspite of following the insitu moisture conservation practices, rainwater surplus do exixt which can be harvested and recycled. It is worth mentioning that up to January – March, 2009, India possessed about 209 per cent potential of rainwater harvesting against utilizing merely 6.9 per cent.
Aims and objectives of water harvesting
The main aim behind water harvesting is to channalise the remaining 13.1 per cent of the rain water to make whole of the country sufficient in water availability during non-monsoon months. To recharge the ground water table is another aim of the rain water harvesting. It is because the water table has gone down and the water has contaminated with heavy metals. Actually, the level of ground water has gone so deep that it touches with the underground rocks, thereby, causing a metal pollution including uranium and fluoride.
According to statistics available with the water resource ministry , long term analysis of ground water levels made by central ground water board indicated decline in ground water level of more than 4m in some parts of 274 district belonging to 16 states (meenakshi sundram , 2014). The main causes for ground water depletion are: rapid urbanization, increasing demand of water for agriculture, industrial and domestic purposes, change in cropping pattern, excessive withdrawal of ground water and poor rainfall. Lack of awareness among people towards water conservation is also one of the reason for depletion of water table. To improve the depleted water table, it becomes very necessary to build up check dams develop watersheds , desilt the ponds, streams and rivers. To develop appropriate land use system to increase the overall productivity of hydrological unit and to develop crop security/food security. For this purpose diversified agriculture is the need of the day.
(To be continued)