Rainfall‐induced ground deformation in southern Africa

Abstract

We present an analysis of ground deformation induced by large‐scale seasonal rainfall in Southern Africa, based on GPS and GRACE time series and on simulations of elastic flexural response to hydrological loading. This large‐scale study including South Zambia, South Angola, North Namibia and North Botswana displays a latitudinal precipitation gradient between tropical to semi‐arid conditions. GRACE data display annual variations in water mass decreasing drastically southwards. GPS time series of three permanent stations located in Zambia, Namibia and Botswana show seasonal synchronous vertical displacements with amplitude decreasing southwards from 4 to 2 cm, with a shift of 2–3 months from the main rainfall season. Flexure simulations integrating rainfall, evapotranspiration, water storage, flood migration and river output produce a ground flexure up to 6 cm with timing in agreement with the GPS time series. It highlights the hydrological buffering of surface aquifer located in the Kalahari sands.