Environmental Monitoring & Assessment Program

Jason R. Hill , Lawrence D. Willis, Richard D. Miller, Mary R. Dail and George J. Devlin

Virginia Department of Environmental Quality, West Central Regional Office, 3019 Peters Creek Road, Roanoke, Virginia

Targeted water quality monitoring has utility for monitoring regulatory compliance of point sources, identifying impaired waters, and for tracking local pollution events. However, it is not appropriate to extrapolate results from targeted stations to unsampled watersheds over large geographic areas. Data to answer such questions are best obtained from sample locations chosen so that all streams have an equal chance of being sampled. T he Virginia Department of Environmental Quality (VDEQ) started a project to assess the utility of a probability-based monitoring program (ProbMon) as an addition to existing targeted and watershed based water quality monitoring programs. ProbMon was initiated to determine the extent of water quality problems with statistical accuracy. However, probabilistic monitoring provides the optimal sampling design to test new water quality monitoring and assessment tools. Data generated from probabilistic monitoring in Virginia has validated biological assessment tools, defended Total Maximum Daily Load (TMDL) results, and helped with water quality standards development.