Over-extraction from shallow bedrock versus deep alluvial aquifers: Reliability versus sustainability considerations for India's groundwater irrigation

The excessive exploitation of groundwater aquifers is emerging as a worldwide problem, but it is nowhere as dramatic and consequential as it is in India, the world's largest consumer, where hundreds of millions of people depend on it. Usually the problem is framed in terms of a long-term decline in water tables and its consequence for extraction costs, resource depletion, and the sustainability of irrigated agriculture. Here a comparative analysis is provided of coupled groundwater, energy, and irrigation dynamics in two groundwater intensive regions in India that differ in their underlying hydrogeology-the Indian Punjab with its deep alluvial aquifers and the Telangana region in south-central India with its shallow hard rock aquifers. Using a simple modeling framework and piezometric and agricultural time series, we show that in shallow aquifers the sense in which extraction is excessive is different, and is related to the short-term reliability of water supply rather than long-term sustainability. This has important repercussions for irrigated agricultural economies.