Groundwater storage change estimation using GRACE satellite data in the Helmand River Basin of Afghanistan

Understanding dynamic changes of groundwater storage and quantifying the trends of groundwater fluctuations in the Helmand River Basin (HRB) aquifers, where the groundwater is the main source for drinking and irrigation applications is significantly important for effective management of groundwater resources. This case study quantifies the changes in groundwater storage over 18 years (i.e., from 2003 to 2021) in the HRB by employing the Gravity Recovery and Climate Experiment (GRACE) observations and Global Land Data Assimilation System (GLDAS) data due to sparse groundwater monitoring networks and lack of ground-based information. The data of observation wells was used to validate the results of the GRACE and GLDAS outputs. The results indicate that changes in groundwater storage on average from 2003 to 2021 are equal to (-112.4 ± 237.14 mm or -2.048 ± 4.32 km 3 /year). In average, during 2003 to 2021 groundwater table decline was -6.10 m in the HRB. The study indicated relatively strong correlation (0.75) between the GRACE derived data and direct in situ measurements. This study highlights the effectiveness of the GRACE-derived data for the reliable estimation of groundwater storage changes in the HRB and may contribute to sustainable groundwater resources management in the region.