Submersed aquatic vegetation (SAV) is a critical component of the Potomac River ecosystem (Fig. 1). Though SAV provides important habitat for fauna and stabilizes bottom sediment, very dense beds may restrict recreational and commercial navigation. Exotic species of SAV are managed by the Metropolitan Washington Council of Governments Potomac Aquatic Plant Management Program (PAPMP). Selected beds of primarily exotic SAV species that limit navigation are harvested mechanically. The program began in 1986 when approximately 40 acres of plants were harvested from 18 sites (Fig.1, Metropolitan Washington Council of Governments 1987). Monitoring efforts are an effective means of quantifying the distribution and abundance of the exotic species, Hydrilla verticillata (hydrilla) and other SAV species. These annual surveys provide a basis for identifying large-scale changes and trends throughout the ecosystem and allow managers to evaluate the effectiveness of resource management policies based on a reliable scientific foundation (Rybicki and Landwehr, 2007). The U.S. Geological Survey (USGS) has monitored the distribution and composition of SAV beds in the fresh and oligohaline (salinity 0.5 to 5) tidal Potomac River since 1978 using transect sampling (1978 to 1981, 1985 to 1987, and 2002) and shoreline surveys (1983 to 2005). The Government of the District of Columbia has monitored the portion of the Potomac and Anacostia Rivers within Washington DC since 1998 (Rottman, 1999; Ryan, 2005, 2006). The species of SAV observed in beds in the tidal Potomac River are incorporated into the Virginia Institute of Marine Science (VIMS) annual report on SAV distribution in Chesapeake Bay.