Water Resources Research Act Program

Details for Project ID 2007WA193B

Lacamas Lake and other Northwest Reservoirs as Bioreactors: How do Dams Affect Downstream Nutrient Transport?

Institute: Washington
Year Established: 2007 Start Date: 2007-03-01 End Date: 2008-08-31
Total Federal Funds: $48,000 Total Non-Federal Funds: $96,550

Principal Investigators: John Harrison

Project Summary: Human-induced nitrogen (N) and phosphorus (P) over-enrichment of surface waters is an important problem in Washington State, throughout the Northwest US, and globally. Dam construction and reservoir impoundment is believed to exert an important control on downstream transport of N and P through watersheds, both within Washington State and beyond. However, the effects of individual reservoirs can be quite variable, with some reservoirs decreasing downstream N and P transport and some increasing downstream transport of these nutrients. In general, the within-reservoir processing of nutrients and the factors controlling this processing are not well understood. We propose to use Lacamas Lake in Camas, Washington as a model system to elucidate the mechanisms influencing the seasonal patterns and magnitudes of N and P storage (and removal) within a seasonally stratified, eutrophic reservoir. Located in Clark County, WA, just 20 freeway miles from WSU-Vancouver, Lacamas Lake is a 303d-listed reservoir that currently experiences high rates of N and P input. As a highly impacted (hypereutrophic) system where nutrient processing signals are likely to be large, Lake Lacamas provides an excellent study system to test established theories and gain new knowledge related to N and P retention and dynamics in eutrophic reservoirs. It also provides an excellent springboard for a broader study of reservoir impacts on nutrient transport through watersheds. We will carry out a program of targeted observation combined with dye addition experiments to gain insight into patterns and controls of nutrient cycling in Lacamas Lake, with specific attention to the role of lake stratification on nutrient export. In addition to our focused study of Lacamas Lake, we will also mine existing data from literature and other data sources for information about reservoir nutrient storage and removal. This information will be compiled into a new database containing information on reservoir characteristics and on water quality upstream and downstream from reservoirs as well as within reservoirs. We will use this dataset to examine potential relationships between N and P storage and independent variables such as lake depth, residence time, nutrient loading rates, and trophic status. The work outlined in this proposal directly addresses a water quality issue with direct relevance to ecological and human health. In addition this project will provide crucial new information about how reservoirs process nutrients in watersheds. It also addresses each of the Water Resources Research Act (WRRA) 104B programs goals for training and outreach.