Terrestrial Water Storage Monitoring from GRACE and Satellite Altimetry in Bangladesh and the Okawango Delta (Botswana)
Andersen, O.1; Freeman, J.2; Bauer-Gottwein, P.3; Butts, M.4; LeMoine, F.5
1Danish National Space Center; 2De Montford University; 3DTU Water and Ressources; 4DHI - Water and Environment; 5NASA GSFC

Merging remote sensing data from GRACE and satellite altimetry is important to monitor the water balance of large regions and can serve as a supplement to existing hydrological data like river gauges and hydrological models. The GRACE gravity changes are analyzed using a local MASCON approach derived by NASA/GSFC, solving for mass change at 10-day intervals using 4 deg X 4 deg blocks from GRACE level 1B data. Satellite altimetry over the region has been retracked using the EAPRS Expert-retracker System in order to derive height of rivers, in particular the Ganges and Brahmaputra rivers. The EAPRS system has the ability to recovers nearly un-interrupted time series over these rivers. GRACE derived mass change from 2002 to 2006 have been studied along with altimetry for the same period.

Bangladesh is prone to flooding and which has a very large annual variation in Terrestrial water storage. The second target region is the Okawanga Delta in Botswana which pulsates at annual scales causing the flooding of large regions and the monsoon related floods in Bangladesh. In particularly, ENVISAT has the ability of modeling the changes upstream the rivers, which is a major causing factor. GRACE gravitmetry can model the integrated amount of ground and river water on monthly to inter-annual scales which is an important parameter for constraining hydrological models.


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