Time‐lapse gravity as a water resource management tool — Applications to unconfined aquifers

Abstract

Time‐lapse gravity surveys involve gravity campaigns conducted at different times. Differences in gravity measured at given locations between the surveys, after corrections for barometric pressure changes, Earth Tides, and instrument drift, reflect changes in subsurface mass. In this study, we associated these mass changes to changes in groundwater storage. We demonstrate that, in unconfined surficial aquifers, water table elevation changes of ca. 70 cm can be detected, and, if drawdown data are available, specific yield, storativity, and specific storage can be estimated (although specific storage is poorly constrained). We present two case studies, one involving an artificial recharge project in which water table changes are mapped via time‐lapse gravity over a ca. 10 km2 region and a second in which estimates of specific yield, transmissivity, and specific storage are obtained at a single location during a pumping test.