Impact of rainwater harvesting on groundwater recharge in water stressed Aravali hill ecosystem

Alarming ground water extraction to expand irrigation in Aravali hill ecosystem disregarding low rainfall, sandy soils and harsh climate created water crisis in this region. Under a corporate supported initiative, 194 earthen dams were constructed and 1250 ha of waste lands were leveled to harvest rainwater to recharge ground water between 2006 and 2013 in 40 villages of Alwar district of Rajasthan. hi one typical village, 15 earthen dams were constructed and 85 ha of private waste lands were leveled. The reservoir areas were contour surveyed to find storage capacities. Daily rainfall and fortnightly observations from seven wells were recorded to find out changes in groundwater level. The records of all the tube wells were compiled by household survey to assess the level of ground water extraction. Between 1982 and 2012, the number of tube wells increased from 2 to 128 lowering mean water table by 3.6 m. 64 shallow tube wells had to be converted to submersible motors from 2007 to 2012. Though 15, 03, 800 cu m rainwater was harvested from 884.89 ha of rocky Aravali hills but this effort could not reverse the trend of ground water depletion. Data revealed that when there was no reservoir in nearby area of observation wells but number of submersible motors were installed on nearby reclaimed lands and cropping pattern changed in favour of vegetable crops; there was clear drop in water table making the scenario unsustainable for irrigated agriculture. Where there were number of reservoirs nearby, the drop was much less in spite of two to three submersible motors nearby indicating chances of sustainability. Out of seven observation wells, only one indicated the chances of sustainability, two showed partial and four no chances of sustainability. The land reclamation activity not only promoted installation of more bore wells on reclaimed land but also reduced water inflow to the reservoirs thus reducing the scope of rainwater recharge. Reducing area under summer vegetable crops, retaining sufficient area under traditional Pearlmillet and Mustard, expanding area under drip and sprinkler irrigation and regulation to control the number of new bore wells appeared the only way out of this complex problem.