RAINWATER HARVESTING FOR FARMLANDS AND PLANTATION

In India agriculture contributes 40% to our country’s GNP and gives subsistence to 70% of our population. And yet 1/3 of our total geographical area is drought –prone because we are dependent upon the monsoons which can be erratic. Drought-prone areas have to be provided water not only for human and cattle consumption but also for irrigation. Whereas even after good monsoons water is not available only because of lack of proper management and storage. Water Management is the cheapest and purest source of water is rain water. Harvesting of the water in pond, lakes, wells, tanks and reservoirs helps to preserve this water so that it can be put to varied uses later on. One of the most effective ways of water management is through farmponding.

In case of farmlands and plantation sites, there is a huge water potential.The water collected in such areas can be conserved in a systematic and scientific way.The downpour during the monsoons can be arrested in low lying depressions called farmponds. The farmponds can be cultured in different agricultural lands irrespective of their soil strata and plot area. Bunds constructed around these ponds prevent the overflow. The surface run-off from all the corners of the site can be diverted to such ponds through trenches. The silt that is carried off by the surface run-off within these trenches is trapped building silt traps. These silt traps are of dimension 2X2X2 cft depending upon the water potential. The size stone jally in these silt traps arrest the silt and allow relatively clean water into the ponds.

These farmponds can be construsted with lining to prevent seepage through soil from the bunds.Use of cast- in-situ concrete, bricks, stone-slabs, precast tiles, precast concrete slabs etc. Introduction of plastics sheets in the form of LDPE film below the hard cover lining is effective in improving water tightness of lining.

Groundwater excavation in India has gone haywire. It is predicted that groundwater is to deplete by 2015 and India is to become water stressed. Digging of Bore wells and Tube wells on a large scale has dried the fractures. This has a devastating effect on agriculture. Defunct Tube wells in farmlands is a common scene. Food production is decreased and has brought drastic changes in demand supply chain therefore increasing foodprices.Thus, there is an immediate need to recharge groundwater. There are different methods to recharge ground water on a large scale. recharging defunct Bore wells is one method among them. Long trenches trenches dug in agricultural fields carry water to such defunct borewell for recharge.

The next immediate option will be the cement ring wells. The sloping gradients have to be cut-down for such wells. The depth being 25ft and the diameter 4ft. after the excavation, few precast cement rings are inserted into the pit with boulders around. The boulders can be of 40mm thickness. This will allow for easy percolation of surface water into the wells.

The surface run-off flowing with high velocity can be checked at check dams and stored in farm ponds. This not only harvests water for farming but also helps keep soil moisture for dry seasons.