Observation-based analysis of groundwater storage in Vietnam’s Central Highlands: influence of hydro-climatic variability

Abstract

This study explores the impact of climatic variability on groundwater storage dynamics in the Central Highlands of Vietnam, focusing on the Sesan and Srepok River Basins. Different from traditional analyses with groundwater levels, groundwater storage variations are derived here from (i) the G3P Gravity-based Groundwater Product based on satellite gravimetry with GRACE/GRACE-FO and (ii) a network of in-situ groundwater level observations converted to basin-average storage with lithology-dependent specific yield estimates. The results show the dominant impact of rainfall variability on groundwater storage variations. Beyond the seasonal scale, non-seasonal storage anomalies can primarily be explained by the accumulated rainfall and evapotranspiration of the previous 9 to 12 months. Weak correlations with ENSO variability indicate lower groundwater storage in the study area during El Niño periods. The evaluation by in-situ observations indicates reasonable performance of G3P for assessing the regional-scale groundwater storage dynamics in the Central Highlands of Vietnam.