+50 Years of Terrestrial Water Storage Variability in Africa’s Transboundary Waters

Authors: Aondover Tarhule*, SUNY Binghamton
Topics: Physical Geography, Water Resources and Hydrology, Africa
Keywords: Africa, GRACE Satellite, hydroclimatic variability, Transboundary river Basins, water resources
Session Type: Paper
Day: 4/5/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Taylor, Marriott, Mezzanine Level
Presentation File: No File Uploaded


Total Water Storage (TWS) anomalies obtained from the Gravity Recovery and Climate Experiment (GRACE) satellites provide unique and additional perspectives about freshwater availability and change globally. GRACE data integrate the impacts of natural and anthropogenic processes on all forms of water resources within the basin, making it especially advantageous in data sparse locations and regions experiencing rapid environmental changes. However, the data suffer the limitation of being relative short, dating back to only 2002. In this study, we reconstruct a 0.5-degree gridded GRACE-TWS for nine major transboundary river basins in Africa. These TRBs encompass 80 percent of the continent’s freshwater resources, support more than 600 million people and depend critically on shared understanding of the dynamics of hydroclimatic variability to support treaties and collaborative water resources management. The reconstruction makes use of Noah Land Surface Model reanalysis data to extend the Terrestrial Water Storage data to 1951. We analysed the reconstructed TWS series for trends, abrupt shifts as well as the dominant modes of variability using wavelet analysis. The results showed significant downward decline in the TWS trends across the northern basins, with relatively short cycles of 1 to 2-year period. The southern basins showed higher variability, insignificant TWS trends and relatively longer periodicities. Furthermore, the gridded TWS showed hotspots or zones of significantly increasing/decreasing TWS trends. The pattern observed is distinct from the spatial patterns exhibited by other conventional datasets. Underscoring the value added of the TWS reconstruction.

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