GSA Connects 2021 in Portland, Oregon

Paper No. 9-6
Presentation Time: 9:30 AM


MACALLISTER, Donald John, British Geological Survey, Lyell Centre, Edinburgh, EH14 4BA, United Kingdom, KRISHAN, Gopal, Water Resources, River Development, Ganga Rejuvenation, National Institute of Hydrology, Groundwater Hydrology Division, Roorkee, 247667, India, BASHARAT, Muhammad, International Waterlogging and Salinity Research Institute (IWASRI), Pakistan Water and Power Development Authority (WAPDA), Lahore, NA, United Kingdom, MACDONALD, Alan, British Geological Survey, Edinburgh, EH14 4AP, United Kingdom and CUBA, Daniela, University of Glasgow, Glasgow, NA, United Kingdom

Northwest India and central Pakistan are vital for food production in South Asia. The region has a long history of major surface and, more recently, groundwater development for irrigation and have become global hotspots of groundwater exploitation. The Gravity Recovery and Climate Experiment (GRACE) satellites, launched in 2002, provide evidence of the scale of groundwater depletion. More recently studies have shown that groundwater depletion is regionally heterogenous and is influenced by a combination of human and climatic factors, including changes in monsoon precipitation and recharge from the regions vast canal network. The areas of most concern for the long-term sustainability of the transboundary aquifer are within the states of Punjab and Haryana in India and Punjab Province in Pakistan.

Recent depletion is set within a much longer history of groundwater level variation spanning the last 150 years. Using a unique long-term dataset, we investigated groundwater level change throughout the 20th century and the first decade of the 21st. The dataset contains time-series from 4028 observation wells and includes 110 years of groundwater level data from 1900 to 2010. Our aim was to: 1) examine changes in post-monsoon groundwater levels during the 20th century and; 2) unravel the influence of canal construction, tubewell development and precipitation on long-term groundwater storage in northwest India and central Pakistan.

We found that for the majority of the 20th century groundwater levels were rising and estimated net groundwater accumulation of c.350 km3 (150-450 km3). Large scale irrigation development via canal construction played a defining role in groundwater accumulation during the early twentieth century. The groundwater depletion that occurred in the first decade of the 21st century, and which we estimate at c.75 km3(estimated range: 25-100 km3), was driven by the superimposed effects of low rainfall and large-scale tubewell development. However, between 1970–2000, when large increases in tubewell irrigation began, groundwater levels stabilised as a result of higher than average rainfall. Our study clearly demonstrates that human activity in the early 20th century increased the total volume of groundwater available prior to the large-scale exploitation that began in the late 20th century.