Abstract:
The groundwater systems of northwest India and central Pakistan are among the most heavily exploited in the world. However, recent, and well-documented, groundwater depletion has not been historically contextualized. Here, using a long-term observation-well dataset, we present a regional analysis of post-monsoon groundwater levels from 1900 to 2010. We show that human activity in the early twentieth century increased groundwater availability before large-scale exploitation began in the late twentieth century. Net groundwater accumulation in the twentieth century, calculated in areas with sufficient data, was at least 420 km3 at ~3.6 cm yr–1. The development of the region’s vast irrigation canal network, which increased ground water recharge, played a defining role in twentieth-century groundwater accumulation. Between 1970 and 2000, groundwater levels stabilized because of the contrasting effects of above-average rainfall and the onset of tubewell development for irriga tion. Due to a combination of low rainfall and increased tubewell development, approximately 70 km3 of groundwater was lost at ~2.8 cm yr–1 in the first decade of the twenty-first century. Our results demonstrate how human and climatic drivers have combined to drive historical groundwater trends.
