The Water Balance of the East African Lakes And its Application to the Study of Past Climates

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Nicholson9973150The large lakes of East Africa are sensitive indicators of climatic change. Fluctuations of these lakes register rainfall variability in a large continental region of the tropics prior to the availability of actual rainfall measurements. In prior work, the P.I. produced detailed reconstructions of the fluctuations of 10 lakes since 1800. To better interpret these fluctuations, an accurate assessment of the water balance of Lake Victoria was made and a hydrologic model of its year-to-year fluctuations was developed. The model was applied to quantifying the rainfall conditions that produced these fluctuations. Here, we propose to extend our work to other East African lakes.The ultimate goals of this study are to produce improved esrtimates of water balance for selected African lakes, to develop models of the lakes' interannual fluctuations, to invert the models to interpret the lakes' past rainfalls, and to determine the lakes' sensitivity to other environmental parameters. The most concern is assessment of rainfall and cloudiness over the lake. Direct information on these terms is so difficult to obtain that they have been assessed from shoreline stations. Because of the influence of the shore, this approach does not provide an adequate picture over the lake itself. In our study, high-resolution satellite data will be used to determine cloudiness and rainfall directly over the lakes. This is particularly important for the larger lakes where mesoscale circulation systems alter the patterns of rainfall and cloudiness.The results of the project will be reliable estimates of water balances for African lakes, simple models of internannual fluctuations, a quantitative assessment of rainfall conditions throughout the nineteenth century, and a generic tool that can be later applied to interpreting paleoclimate from the high-resolution sedimentary record.