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Satellite Observations of the Elephant Butte Reservoir in New Mexico
Schmugge, T.; Bleiweiss, M.; Stein, W.
New Mexico State University
For many reservoirs there are considerable fluctuations in levels
as water is drawn down for irrigation purposes. We present
satellite observations of changes in the surface water area as
evidence of this drawdown. Since the launch of NASA's Terra
satellite in December 1999 the Advanced Spaceborne Thermal
Emission and Reflection (ASTER) radiometer has made more than 30
observations of the Elephant Butte Reservoir located on the Rio
Grande river in central New Mexico including night-time
observations. The first observations were in June 2000 and
continue to the present. This period includes low water levels
resulting from the the recent drought conditions and the earlier
full high water conditions in 2000, resulting in a 25m change in
water level. This change indicated a reduction of the water
storage by more than half. The area of the reservoir was
estimated for each of these scenes and compared the with known
water levels. Both visible reflectance and the thermal infrared
data were used. These spectral regions provide good contrasts
between water and surrounding land which makes the area
estimation straightforward. A large range in surface water area
was observed from 30,000 km*2 to more than 75,000 km*2. An
approximately linear relation between area and water level was
found. In addition to the area measurements there were surface
temperature observations from both ASTER and MODIS (almost daily)
. We also plan to explore the use of satellite altimetry for
water level determinations.almost daily
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