Bi-decadal groundwater level trends in a semi-arid southindian region: Declines, causes and management

Abstract

Study region: Three districts in crystalline aquifer region of semi-arid south India.Study focus: India, world’s largest groundwater user (250 billion m3yr−1) has been reportedto experience declining groundwater levels. However, the statistical significance of thedecline has not been analyzed to separate human effects from natural variability. Trendsin groundwater levels in three administrative districts of south India were analyzed andexplained through changes in irrigation, rainfall, and agricultural power subsidy.New hydrological insights for the region: Contrary to common perception of widespreadgroundwater declines only 22–36% of the wells showed statistically significant declines.The use of well depth during dry well periods may slightly underestimate the number ofdeclining wells (by 1%) and rate of decline. Increase in groundwater irrigated area combinedwith rainfall and power subsidy policy, were the main causative factors for the decline.Groundwater decline after implementation of free-electricity policy in 2004 confirmed thenexus between power subsidy and groundwater. These declines are likely to worsen due tofuture well drillings. Trends in other regions with similar hydro-geologic conditions needto be analyzed to verify groundwater declines and its linkages with power subsidy. Onceestablished, reforms in power subsidy and well permit policy along with conversion toefficient micro–irrigation may be needed to maintain or enhance groundwater availabilityin the crystalline aquifer region of India (240 million ha).