Elephant Butte Reservoir 2007 Sedimentation Survey

摘要

Reclamation surveyed Elephant Butte Reservoir in October 2007 to develop updated reservoir topography and compute the present storage-elevation relationship (area-capacity tables). The underwater survey was conducted near water surface elevation 4,327 feet (project datum). The project datum is 43.3 feet less than the National Geodetic Vertical Datum of 1929 (NGVD29) and 45.5 feet less than the North American Vertical Datum of 1988 (NAVD88). The underwater survey used sonic depth recording equipment interfaced with a real-time kinematic (RTK) global positioning system (GPS) that provided continuous sounding positions throughout the underwater portion of the reservoir covered by the survey vessel. The reservoir topography was determined by importing digital images of the contour lines from the U.S. Geological Survey quadrangle (USGS quad) maps of the reservoir area, 2004 and 2007 aerial data that covered large portions of the reservoir, and 2007 bathymetric data. As of October 2007, at reservoir water surface elevation 4,407.0 feet, the surface area was 35,825 acres with a total capacity of 2,024,586 acre-feet. Since 1915 and the initial reservoir filling, 610,214 acre-feet of sediment have accumulated in Elephant Butte Reservoir. Since the last reservoir survey in 1999, the reservoir volume has increased 1,228 acre-feet due to the dewatering and resulting compaction of the previous measured sediments that have been exposed during the extended drought conditions. The average annual rate of sediment accumulation since 1915 is 6,575.6 acre-feet compared to the 1999 study computation of 7,253.2 acre-feet.