Terrestrial and groundwater storage characteristics and their quantification in the Chitral (Pakistan) and Kabul (Afghanistan) river basins using GRACE/GRACE-FO satellite data

In Pakistan and Afghanistan, intensive groundwater abstraction has accelerated socioeconomic development, but it also endangers the long-term sustainability of groundwater resources. Sustainable water resource management throughout river basins requires a spatiotemporal analysis of groundwater storage changes, but continuous groundwater monitoring is critical while there are few observation wells in the Chitral Kabul River Basin (CKRB). Therefore, this study uses total water storage (TWS) data from the Gravity Recovery and Climate Experiment (GRACE) and its Follow-on (GRACE-FO) and the Global Land Data Assimilation System (GLDAS) model water storage components, such as surface runoff (Qs), soil moisture content (SMS), and snow water equivalent (SWE) to determine the characteristics of groundwater storage (GWS) variations from 2003 to 2021. The seasonal decomposition LOESS method (STL) was used to assess the long-term trend, seasonal trend, and associated uncertainty of TWS and GWS time-series, while Mann-Kendall and Sen's slope estimator was used to detect and quantify the increasing and decreasing trend values of TWS and GWS time-series. The results showed that TWS indicated a general decreasing trend of − 3.67 ± 0.98 mm/month while GWS indicated a harsh declining trend of − 7.83 ± 0.52 mm/month from 2003 to 2021 in CKRB. The validation of GRACE-derived GWS results showed a correlation of R2 = 0.47 in comparison to in situ GWS. Spatially and temporally, according to sub-basins of CKRB, the more severe decline of TWS in Chitral-Kunar (− 2.66 mm/year) and GWS in Swat (− 4.34 mm/year) was observed. This research would be insightful to estimate the agroeconomic impact of the intensive groundwater in CKRB and its sub-basins.