Discharge of the Congo River Estimated from Satellite Measurements
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Date
2010-06
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The Ohio State University
Abstract
The Congo River basin has little in situ data which limits our hydrologic knowledge of the region. Hydrologists using remote sensing data must rely on visible band frequencies or radar technologies (e.g., LandSat and various SAR missions) for measurements of river channel width, length and water surface elevation. Our objective in this study is to determine the discharge of the Congo River and several of its largest tributaries, using only remotely sensed data. Data sets showing where water is found (Global Rainforest Mapping, or GRFM) are combined with data sets showing elevation (Shuttle Radar Topography Mission, or SRTM) to determine the slope of the water. Measuring widths is done with an algorithm or is estimated based on catchment area. We also select a value to express the river channel roughness (Manning’s n). To calculate slope, we used measured water surface heights (from SRTM) and flow distance values (from GRFM). These variables are combined in Manning’s equation to estimate the discharge of the river. We collected a large amount of SRTM elevation data throughout the basin rivers. The Congo mainstem has 159,457 total elevation data points, while some of the major tributaries have between 1,000 and 36,000 points. Slope values were found in linear segments with sharp breaks in between the segments. The river’s interaction with topography is clear when the location of the breaks in slope are noted on a map. River slopes in the eastern mountains (part of the high plains surrounding the interior lowlands) range from 31.21 to 135.72 cm/km. Slopes in the interior are low, ranging from 5.39 to 10.79 cm/km.
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Keywords
Congo River, Satellite hydrology, SRTM, GRFM