DISCHARGE OF THE CONGO RIVER FROM SATELLITE MEASUREMENTS

The Congo River in central Africa is the world's second largest river (based on drainage area and discharge); yet very little hydrologic data has been collected from this region. The lack of data makes it an important region for scientists to focus on, particularly because the region gets heavy precipitation on both sides of the equator at different times of the year, due to the Intertropical Convergence Zone (ITCZ), a low pressure zone around the equator which results in vast amounts of rain. Deforestation is also changing the hydrology of the region, runoff now flows more directly into the river, increasing the flow and stripping nutrients out of the soil. Many satellite missions have been launched that image the earth with visible band frequencies or with radar technologies (e.g., LandSat and various SAR missions, respectively), but none specifically designed to look at water storage changes. Hydrologists using remote sensing data rely on the images from other satellite missions for measurements of width, length and elevation. The Congo River has few functioning gauges and is politically unstable, thus further limiting our hydrologic knowledge. Ultimately we want to determine the discharge of the Congo River and several of its largest tributaries, using only remotely sensed data. Data sets that show where water is found (Global Rainforest Mapping or GRFM) can be combined with data sets that show elevation (Shuttle Radar Topography Mission or SRTM) and the slope of the water can be determined. Using width measurements, estimates of depth and a number to express the river channel roughness, Manning's Equation can be applied to find the discharge of the river. While our Congo study has only just started, it is based on years of Amazon remote-sensing research. In the Congo, we expect to find river widths despite the complex braided nature of the channels, changes in water storage between high and low water and the total discharge.