Acquire Sedimentation Data to Promote Reservoir Sustainability and Advance Watershed Science

Acquire Sedimentation Data to Promote Reservoir Sustainability and Advance Watershed Science

National Institute for Water Resources, Water Resources Research Institute Program

3/1/2012 - 2/28/2013

Hawaii’s reservoirs face growing scrutiny due to heightened dam safety and flood control concerns, increasing water demands, and uncertain water pollution effects. Although the National Inventory of Dams (NID) includes records for about 138 Hawaii structures, information about associated sedimentation was not included in the National Reservoir Sedimentation Database (RESSED). The Sedimentation Subcommittee of the USGS Advisory Committee on Water Information considers quantification of reservoir capacity loss rates as a high priority for maintaining reliable water supplies, and notes that reservoir capacity information is fundamental with respect to irrigation, flood control, power generation, recreation, environmental flows, and downstream channel morphology. Therefore, I have collected preliminary data for submission of a larger proposal to acquire information about Hawaii reservoir sedimentation and upload data to RESSED. This project directly addresses WRRC research priorities for water supply and water system infrastructure, with results that apply to additional research on water quality and water institutions.

RESSED records are based on data acquired from repeated bathymetric and topographic surveys that indicate changes in reservoir bed elevation over time. Thus, the first step in the research was obtaining as-built bed elevations for reservoirs listed in the NID, followed by the acquisition of any existing data from subsequent surveys. Based on the information generated, the final step was developing a sampling and analysis plan for a field investigation to fill gaps in the historic record and establish new baselines for informing reservoir management, water resource planning, and future watershed research.

The sampling and analysis plan explored the use of advanced technologies for acquiring bathymetric data and measuring bed sediment accumulation, as well as more conventional coring of reservoir bed material to study its physical, chemical, and biological characteristics. In this way, the sampling effort also contributed to our understanding of watershed erosion rates and pollutant loading dynamics, and provided information for designing a related project to complete a statistically-valid survey of statewide lake and reservoir water quality.

Collaborators and funding sources include a multitude of federal and state agencies—particularly the USGS, U.S. Army Corps of Engineers, U.S. Department of Agriculture, and State Department of Land and Natural Resources (Engineering Division) — as well as private reservoir operators who are struggling to meet regulatory requirements. The work is also of interest to UH colleagues in a variety of disciplines, especially WRRC, Engineering, CTAHR, and Geography.

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