Spatial Variability of Groundwater Storage in Pakistan

In recent years, the use of Gravity Recovery and Climate Experiment (GRACE) data has emerged as a valuable tool for investigating groundwater resources in data-scarce regions. This chapter reports on a study carried out to investigate and understand trends in the spatial variability of groundwater storage of Pakistan. We used three sets of GRACE data in this study: the data of Center for Space Research (CSR); Jet Propulsion Laboratory (JPL); and GeoforschungsZentrum Potsdam (GFZ). These datasets cover the period 2003 to 2016 at a spatial resolution of 1.0° × 1.0°. The rate of change in groundwater storage was assessed using Sen’s slope and the significance of the change was estimated using a modified version of the Mann-Kendall (MK) test. The results showed that the degree of groundwater storage change was different across different regions. The decline in groundwater storage was noticeably higher in areas of intensive agriculture, with a range of −9.02 to −11.3 cm/year, and was higher in the south of the country compared to other parts. The MK test revealed the declines were significant for 35 grid cells across different parts of the country. The findings confirm the need for measures to be taken to prevent overuse of groundwater resources to avert a crisis in the near future.