State Water Resources Research Institute Program

Project ID: 2008WA235B
Title: Reservoir Sediments: Biofilter or Environmental Liability?
Project Type: Research
Start Date: 3/01/2008
End Date: 2/28/2009
Congressional District: Washington 17
Focus Categories: Hydrogeochemistry, Nutrients, Water Quality
Keywords: eutrophication; reservoirs; nitrogen; phosphorus; nitrous oxide; denitrification;
Principal Investigator: Harrison, John
Federal Funds: $ 25,000
Non-Federal Matching Funds: $ 50,426
Abstract: Human-induced nitrogen (N) and phosphorus (P) over-enrichment of surface waters is an important problem in Washington State, throughout the Northwest US, and worldwide, and has been associated with a host of environmental and economic concerns. It is likely that N and P enrichment of surface waters is affected significantly by another, co-occurring, regional and global change: the construction of dams and impoundment of reservoirs. Predictions of river nutrient transport are particularly sensitive to how reservoirs are treated in existing models, yet relatively little is known about how reservoirs process nutrients. Though reservoirs are generally thought to reduce N and P transport by trapping nutrients in sediments or converting them to inert forms via sediment processes, the effects of individual dams can be quite variable, and in some systems reservoirs have actually been observed to enhance downstream nutrient transport. Based on other work in aquatic systems, the role of sediments in controlling reservoir N and P processing is likely to be critical. We propose to use Lacamas Lake as a model system to elucidate how sediment processes influence the seasonal patterns and magnitudes of N and P storage, removal (and possibly regeneration) within a nutrient rich reservoir. As a highly impacted, local system where nutrient processing signals are likely to be large, Lacamas Lake provides an excellent study system in which to test established theories and gain new knowledge related to N and P retention and dynamics in nutrient-rich reservoirs. It also provides an excellent springboard for a broader study of reservoir impacts on nutrient transport through watersheds. We propose to use sediment core incubation experiments and sediment traps to quantify rates and identify controls of net N and P exchange between sediments and overlying water in Lacamas Lake. This work would build upon, and greatly enhance current research on Lacamas Lake water-column N and P dynamics being carried out by our group. Hence, the work outlined in this proposal would provide crucial new information about how reservoirs process nutrients, thereby helping watershed scientists model the impact of dams on N and P transport at local, regional and possibly global-scales. The proposed work would also contribute to a solid foundation of data and research infrastructure, which our group would use to develop peer-reviewed publications and additional proposals for extramural funding.

Progress/Completion Report, PDF

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