This pilot study examines the distribution of freshwater weed species in Washington State lakes. Lakes with invasive species were identified using a GIS database compiled through the Washington Department of Ecology's (DOE) Freshwater Aquatic Weed Program, which has monitored the distribution of 23 aquatic invasive non-native plants since 1991. The 494 lakes in the DOE database were compared with a GIS database of Washington State lakes classified by lake type. Using a series of scoping questions outlined in a Decision Support System for Lake Shoreline Assessment developed for the Washington Department of Ecology by the Geo-Ecology Research Group, over 1100 lakes over 20 acres in size have been classified into several principal types: coastal, coulee, glacial drift plain, kettle, glacial scour, cirque, crater, oxbow, and impoundment lakes. These scoping questions are being used to further classify other smaller lakes found in the DOE database as well.
A Microsoft Excel database has been created for various physical lake and human use variables for the lakes found in both databases, and potential relationships and differences are being statistically analyzed using chi-square and Mann-Whitney U nonparametric tests (p<0.05). The distribution of aquatic weed species are being analyzed with regards to a variety of environmental characteristics and potential controlling factors, including lake characteristics such as type, hydrologic linkages, morphology (e.g. size, perimeter, perimeter-area ratios, depth), water quality parameters (when available through the DOE Lake Water Quality Monitoring Program), and elevation, as well as anthropogenic characteristics such as presence of boat launches, proximity to cities, and other estimates of human use such as proportions of lake shoreline land use types, county densities and number of licensed boats in each lake's county.
Gabriel, A., and J. Gray. 2009. Assessment of potential e nvironmental controls of invasive aquatic plants in Washington State lakes. Poster presented at Water and Land Use in the Pacific Northwest: Integrating Communities and Watersheds , Skamania Lodge, Stevenson , Washington , November 4-6, 2009 .