Water discharge in East Africa from grace, satellite altimetry and Landsat data

Abstract

In this study, lake level changes in East Africa (i.e. Lakes Victoria, Tanganyika, and Malawi) are investigated using satellite gravimetry and altimetry as well as hydrological models and Landsat data from January 2003 to January 2013. The fitted trend of the time series of altimetric lake height shows a significant decline in the average lake level for all of the three lakes between 2003 and 2006 with different rates. The main reason of this significant declination is the drought happened in much of East Africa during this period of time. After 2006, the lake level started to increase rapidly until 2009 for Lakes Victoria and Malawi and until 2010 for Lake Tanganyika. After which it shows a slight increase for Lakes Victoria and Tanganyika while it shows a significant decrease between 2010 and 2012 with −215 mm/yr for Lake Malawi. For each lake, the STL decomposition plot of the monthly GRACE TWS shows the same pattern as the time series of altimetric lake height. It shows a significant decrease in the TWS between 2003 and 2006 with the max rate in Lake Victoria, followed by a significant increase until 2009. After which it shows a slight increase for Lake Victoria while Lakes Tanganyika and Malawi experienced a reduction between 2010 and 2013. Water discharge in East Africa is also similar with results from Landsat-7 ETM+ data.