Terrestrial water storage variations in Lake Victoria Basin from multi-source data

In this paper, GRACE Release-06 monthly time-variable gravity field released by CSR, satellite altimetry data, land surface model data, precipitation data and evaporation data from January 2003 to June 2017 over the Lake Victoria Basin are used to analyze the spatiotemporal variability of terrestrial water storage (TWS), and compare the effect of forward modeling method and basin scale factor method on the correction of leakage error in the basin. Our analysis indicates that the forward modeling method can correct leakage errors effectively, which is applied to recover the signal attenuation caused by leakage in our study. By using the GRACE Release-06 satellite gravity products, a significant increase trend is detected in the basin from January 2003 to June 2017, the estimated rates from spherical harmonic coefficient products and Mascon products are 14. 9 mm.a(-1) and 16. 7 mm.a(-1), respectively. The observation error from GRACE Release-06 projects is smaller than that of Release-05, while the results from Release-05 underestimated the change rate of water storage. From January 2013 to February 2016, both satellite gravimetry and satellite altimetry detect water storage increase over the Lake Victoria Basin while hydrological models show a decrease which is speculated to be caused by dam impoundments. Influenced by El Nino events, rainfall in the basin decreased, which further cause the terrestrial water storage decrease from March 2016 to June 2017. During this period, the decrease trend in TWS detected by GRACE spherical harmonic coefficient products and Mascon products was -100. 3 mm.a(-1) and 129. 7 mm.a(-1), respectively. The results of our study show that satellite observations can provide a feasible way to analyze the impact of human activities and natural changes on regional water storage change in the absence of direct in-situ observation data, which also provides a reference for studying the variations of water storage in lake basins in China.