A study of lakes and wetlands in Africa from land surface modeling

Lakes and wetlands are of great importance to the socio-economics of the African continent. However, information about variations in surface water storage in event the largest lakes is surprisingly sparse. Satellite altimeters now provide some information about variations in lake surface elevation and surface extent information is available from visible and other sensors. But for most lakes the variations of lake water storage (regardless of size) at interannual and interseasonal time scales is mostly unknown, and the variations due to long term climate change are beyond the present state of knowledge. We use a modified version of the Variable Infiltration Capacity (VIC) macroscale hydrology model, in combination with remote sensing data, to help understand the water storage variation of lakes and wetlands across Africa. We use a 55-year (1952-2006) record of land surface climate data to produce hydrological simulations with the VIC model, including changes in lake/wetland extent and storage as well as the basin-wise water budget over Africa. The model is calibrated to observed runoff data wherever available. For representative large lakes (e.g., Lake Chad, Lake Victoria) the variations of water surface elevation and/or lake surface area as simulated by VIC are evaluated using remote sensing data and gauge observations. We also evaluate the contribution of lake storage to aggregate continental water storage variations over the half-century simulation, and the nature of decadal scale variations within the simulated record.