Qualitative Approach for On-farm Water Conservation in a Semi-arid Region

Conservation of available surplus water has been dealt with a qualitative approach. The investigations have been carried at the Najafgarh Block in West Delhi, a semi-arid, peri-urban area, getting an average rainfall of 451 mm. The block is currently facing water shortage due to lowering of water table and deterioration in ground water quality. Past studies in this region revealed an average natural recharge of only 13%, indicating vast possibilities of conserving part of the remaining 392mm (average), which is lost either as run-off or evaporation. Qualitative conservation has been based on the quality of both, the available surplus and that of the ground water of the area under study. Ground water samples collected from 31 villages during the year 2001–2002 representing different geographical locations of the block were analyzed for major ions and were finally classified in two groups on the basis of EC (electrical conductivity) and SAR (sodium adsorption ratio) values. The first group corresponds to the villages with ground water up to 4.62 dS m⁻¹ EC and 18 SAR (the limits obtained by merging acceptable and the tolerable values of both, in relation to irrigation). The second group corresponds to all other villages having ground water of very poor quality i.e. exceeding 4.62 dS m⁻¹ EC and 18 SAR ie limits of both, beyond which it is unfit for irrigation for most of the crops. The villages with ground water of the first group were designated as fit for both, for irrigation as well for receiving water for artificially recharging of the aquifer, provided, available surplus for conservation also belonged to the first group. Similarly, if the ground water as-well/or the available surplus, were of the second group, i.e. of rejection level, the conservation was suggested only by storing the water at the surface. Following the information received through the landsat remote-sensed pictures about availability of excess runoff water during the monsoons, an old pond situated in such a location at the village Mitraun (ground water EC 8.91 dS m⁻¹) was adopted for conservation of excess water available. In the absence of enough surplus during the non-monsoon period, waste water from the village was also directed to collect in this pond, with joint efforts. The quality of the conserved water was monitored from time to time and subsequently used for sustaining the crops grown around this area.