Integration of Altimetric Lake Levels and GRACE Graimetry over Africa
Newcastle University, UNITED KINGDOM
Satellite altimetric measurements over lakes and reservoirs provide the water level variation which when combined with the areal extent give a time series of water storage change. In this study we consider the major lakes in Africa, namely Lake Victoria, Lake Tanganyika, Lake Malawi, Lake Turkana, Lake Albert etc. For major lakes the change in water storage has the potential to provide a gravitational signal that can be observed by the GRACE gravity field mission. In this study we utilise ENVISAT altimetry both directly from the GDRs and from retracking to provide a measure of the water storage change with the altimetric lake heights compared against available gauge data. The water storage change is subsequently converted to a surface mass change to simulate the gravitational signal sensed by the GRACE mission. Removal of the lake variation signatures and hydrology from the GRACE time varying gravitational field is then interpreted in terms of subterranean groundwater change.