HR: 11:20h
AN: H22C-05    [Abstracts]
TI: Calculation of River Discharge and Prediction of Lake Height from Satellite Radar Altimetry: Example for the Lake Chad Basin
AU: * Coe, M T
EM: mtcoe@wisc.edu
AF: Center for Sustainability and the Global Environment, University of Wisconsin-Madison, 1710 University Ave, Madison, WI 53726 United States
AU: Birkett, C M
EM: cmb@nemo.gsfc.nasa.gov
AF: Earth System Science Interdisciplinary Center, University of Maryland, Biospheric Research Branch, Mailcode 923 Building 33, Room F124 NASA/Goddard Space Flight Center, Greenbelt, MD 20771 United States
AB: The application of satellite radar altimetry to the determination of lake and river elevations has been used in numerous projects, and is well validated. Here, we show that with the aid of ground-based information, this technique can be extended to determine river discharge and predict downstream lake and marsh height. The Lake Chad basin provides an ideal case study due to its well-known hydrology, complex lake and marsh morphology, and because prediction of lake and marsh height has been identified as potentially useful to people living in the region. Altimetric stage measurements from the TOPEX/POSEIDON satellite, at the Chari/Ohuam confluence estimate river discharge about 500 km downstream at N'Djamena 10-days in advance (r$^{2}$ = 0.9611). Via simple linear correlation methods, the stage measurements successfully estimate the height of the permanent waters of the lake (600km downstream) 39 days in advance (r$^{2}$ = 0.9297). Predicting the water height on the western marshes of the lake-bed is poorer (r$^{2}$ = 0.7958) due to a change in response time of the local stage to the seasonal floods coincident with an observed increase in mean water level in the latter half of the 1990s. Before 1997 a 96-day phase lag results in the best fit (r$^{2}$ = 0.6463). After 1997 the best fit is obtained with a 66-day phase lag (r$^{2}$ = 0.8139). The excellent river discharge and lake height predictions show that the altimetry is a useful tool where ground-based data is difficult to obtain and where rapid water resource assessment is desirable.
DE: 1655 Water cycles (1836)
DE: 1860 Runoff and streamflow
DE: 1640 Remote sensing
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting