IGCP 565 Project Workshops

IGCP 565 Workshop 4: Integration of geodetic observations and products in models of the hydrological cycle Support for water management through hydrological models and data assimilation November 21-22, 2011 Johannesburg, South Africa

GRACE: Monitoring River Basins in Africa

Laurent Longuevergne
Géosciences Rennes, Université de Rennes, FRANCE

Geodesy is the discipline studying the earth’s shape and its gravity field. This tutorial talk highlights the interest of gravity measurements, which may be interpreted as water mass variations on the continents and provide significant supplementary observation for hydrological studies.

We will begin with a short course on the physics behind hydro-geodesy and present the characteristics of both ground-based and satellite geodetic instruments. GRACE is a new satellite, the first of its kind, able to measure total water storage variations within basins larger than 200 000 km². Total water storage may be separated into surface water, soil moisture and groundwater contributions. Therefore, there is a growing interest in using GRACE to monitor aquifer storage variations and use it as supplementary information to discharge for hydrological model validation/calibration. Another point of interest is related to the satellite ability to measure the long-term trends in water storage variations, i.e. the impacts of climate change and water management policies. Several case studies will be shown, highlighting the interest of grace in different contexts, including a joint discharge/GRACE calibration of SWAT hydrological model on the entire African continent.