Amazon and Mississippi River Basin Discharge Estimated From GRACE and a Land-Atmosphere Water Balance

Monitoring global freshwater discharge is critical to understanding a range of climatologic, geomorphologic, hydrologic and ecologic Earth system processes. However, no comprehensive global streamflow observing network for the world's major continental watersheds currently exists. Here we propose a method for estimating monthly basin discharge for large river basins based on the use of new GRACE estimates of terrestrial water storage changes in a coupled land-atmosphere water balance. The method was tested on the Amazon and Mississippi river basins, and could ultimately be applied to the major drainage regions and river basins of the globe. Results for both basins were encouraging. Using GRACE land water storage changes (which include changes in groundwater storage) in the water balance method may result in more holistic estimates of basin discharge that include not only streamflow, but the net of surface, groundwater and tidal inflows and outflows.