History meets hydrology in a South Indian district's perilous water gap

Kolar district, in India’s southern state of Karnataka, has been known for centuries as a district of tanks: its landscape is dotted with nearly 3,000 surface reservoirs excavated by successive ancient kingdoms to secure water for household use, livestock, irrigation and groundwater recharge. These tanks, together with shallow open wells, were the predominant sources of irrigation water up until 1985.

Then the flow began to diminish, and farmers started extracting groundwater from deeper aquifers to irrigate fields. By 2000, farmers could no longer rely on Kolar’s mostly dry ancient tanks; irrigation had shifted to borehole wells. Now a district of boreholes, Kolar has also become one of the most water-stressed districts in South India, with the gap between groundwater supply and demand growing by the year…