Glen Canyon Dam Adaptive Management Program Administrative History
This administrative history of the Grand Canyon Dam Adaptive Management Program (GCDAMP) includes government reports, oral history interviews and other relevant information about Colorado River law, environmental protection law, hydropower regulation, the Glen Canyon Environmental Studies that served as a precursor to GCDAMP, and the activities of the Adaptive Management Work Group, the Technical Work Group, and the U.S. Geological Survey’s Grand Canyon Monitoring and Research Center.
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- Creators: Gloss, Steven P.
- Creators: Pratson, Lincoln
Between 1999 and 2005, drought in the western United States led to a >44 m fall in the level of Lake Powell (Arizona-Utah), the nation's second-largest reservoir. River discharges to the reservoir were halved, yet the rivers still incised the tops of deltas left exposed along the rim of the reservoir by the lake-level fall. Erosion of the deltas enriched the rivers in sediment such that upon entering the reservoir they discharged plunging subaqueous gravity flows, one of which was imaged acoustically. Repeat bathymetric surveys of the reservoir show that the gravity flows overtopped rockfalls and formed small subaqueous fans, locally raising sediment accumulation rates 10–100-fold. The timing of deep-basin deposition differed regionally across the reservoir with respect to lake-level change. Total mass of sediment transferred from the lake perimeter to its bottom equates to ~22 yr of river input.
This report is an important milestone in the effort by the Secretary of the Interior to implement the Grand Canyon Protection Act of 1992 (GCPA; title XVIII, secs. 1801-1809, of Public Law 102-575), the most recent authorizing legislation for Federal efforts to protect resources downstream from Glen Canyon Dam. The chapters that follow are intended to provide decision makers and the American public with relevant scientific information about the status and recent trends of the natural, cultural, and recreational resources of those portions of Grand Canyon National Park and Glen Canyon National Recreation Area affected by Glen Canyon Dam operations. Glen Canyon Dam is one of the last major dams that was built on the Colorado River and is located just south of the Arizona-Utah border in the lower reaches of Glen Canyon National Recreation Area, approximately 15 mi (24 km) upriver from Grand Canyon National Park (fig. 1). The information presented here is a product of the Glen Canyon Dam Adaptive Management Program (GCDAMP), a federally authorized initiative to ensure that the primary mandate of the GCPA is met through advances in information and resource management. The U.S. Geological Survey`s (USGS) Grand Canyon Monitoring and Research Center (GCMRC) has responsibility for the scientific monitoring and research efforts for the program, including the preparation of reports such as this one.