Groundwater Trends and Availability Under Current and Future Groundwater Withdrawals and Climate Scenarios in Semi-arid India

Abstract:

Irrigation withdrawals have caused groundwater depletion, decreased surface flows and water quality problems in many parts of the world including India. Anticipated increase in groundwater demand and climate change is likely to exacerbate the problem. This study investigated long term (1990-2012) groundwater level trends in hard rock aquifers of semi-arid south India and used an integrated hydrologic model MIKE SHE/MIKE 11 to analyze the effects of changes in groundwater withdrawals and climate on groundwater and surface water flow and levels. Contrary to the common perception of widespread groundwater declines, statistical trend test results showed significant declines in only 22-36% of the wells in a three district region (3.15 million ha). Free electricity policy for farmers, implemented in 2004, and increased irrigated area were the two main causal factors. Groundwater levels in up to 76% of these wells showed significant decline after the subsidy (2005-2012) indicating the nexus between energy and groundwater. An integrated hydrologic model, developed using long-term monitoring data for a watershed (320 ha) in the region, performed well in simulating surface and groundwater levels. Compared to the current withdrawal scenario, prolonged hydrologic drought and decreased surface flows were predicted under future withdrawal scenarios. Future (2040-2069) climate scenarios from five General Circulation Models (GCMs), showed increased rainfall and flooding in the watershed. Although, projected increase in rainfall under the climate change scenarios is likely to provide opportunities for capture and reuse of surface flows, earlier well drying, and increased frequency and duration of hydrologic drought is likely to affect livelihoods of millions of small-scale farmers in this hard rock aquifer region. Several management options including changes in power subsidy and implementation of efficient irrigation systems, effective institutional mechanism to regulate groundwater, and storage and use of excess runoff, were evaluated to maintain or enhance the future groundwater availability.