Online altimetry service for hydrology: The CASH project
CASH « Contribution of spatial altimetry to hydrology » is a project funded by the French Ministry of Research and Technology (Réseau Terre et Espace). The coordinator of the project is IRD (Institut Français de Recherche pour le Développement) and the industrial partners are CLS (data supply from satellite-based systems for studying and monitoring the environment) and BRLi (consultant in water and the environment). The scientific teams involved are LEGOS (altimetric and geodesic data processing and interpretation), LMTG (hydrology and geodynamic of the great river basins, in particular the Amazon basin), and ESPACE (remote sensing, reception station network and decision support systems). The first goal of the project was to determine the ability of radar altimetry to measure the elevation of continental water bodies. It was then to define the scientific and technological environment necessary to complement the existing in-situ gauges network, or even to substitute spatial measurements to some distant gauges, delivering in several months unprecise or irregular data, or to gauges that have swiched off. The target was therefore the definition of a global, standard, fast and long term access to a set of hydrological data concerning the greatest river basins in the world.
Specific aims are then:
- Create an elevation database for the water bodies of eight great basins (Amazon, Congo, Ganges, Yangtse, Parana, Lena, Mekong, and Danube) from T/P GDR (Topex/Poseidon Geophysical Data Records)
- Improve T/P and Jason data by using retracking algorithms and geophysical/environmental corrections designed specifically for continental waters
- Define and develop an online demonstrator of a decision support system for the test site of the Amazon basin able to get from distant database and mix models and processes, spatial data and in-situ data.The demonstration will apply to some decisional environment implying key hydrological knowledge such as flow modeling for a given reach, calculation of the volume of water potentially stored in the inundation plains, elevation/discharge conversion at a given “virtual” gauge (or intersection between radar satellite track and river), retrieving of water height value at any point of the hydrological network by spatial interpolation between satelllite tracks including for gauge levelling, spatial interpolation conversion of elevation at virtual gauge measured each ten days (for T/P) in daily water height, design of an optimum in-situ gauge network for a given uncertainty at the virtual gauges.