Determination of Groundwater Storage Variation, Deficit, and Abstraction in Afghanistan and the Assessment of the Evolution of Vadose Zone in Kabul City

Abstract

Groundwater is Afghanistan's main water supply resource, but the insufficient information and mismanagement of the surface and groundwater system have resulted in an alarming shortage of this precious resource. The monthly groundwater storage variation (Δ GWS) has been calculated in millimeter (mm) with a trend (mm/month) for the time interval of April 2002-October 2021 using the Gravity Recovery and Climate Experiment (GRACE) dataset for five major river basins of Afghanistan. A maximum and a minimum deseasonalized Δ GWS are observed at Amu Darya (246 to -253 mm) and Hari Rud (89 to -102 mm) basins, respectively. Subsequently, the GWS deficit (GWSD) and GWSD index (GWSDI) were calculated, and a negative GWSDI value signified the groundwater drought. Analysis of the GWS abstraction (GWSabs) has also been carried out for the entire country. The estimated GWSabs trend gives a maximum value of 12.60 mm/year in the northeast and southwest parts of the country. A spatiotemporal analysis showed the maximum GWSabs variation up to 23.12 mm in 2021. Two phases of land deformation were determined in Kabul City using the interferometric synthetic aperture radar (InSAR) technique. In phase-I (2015-2017), there is a gentle negative trend [-20.66 mm/year in Upper Kabul (UKBL) and -18.54 mm/year in Lower Kabul (LKBL)], but in phase-II (2018-2020), there is a high negative trend (-151.34 mm/year in UKBL and -145.32 mm/year in LKBL). Overall, the entire country is experiencing a severe groundwater decline, apparently from the interplay of hydroclimatic and anthropogenic factors, which are most dominant in the Southern and Western parts of Afghanistan.