Long-Term Large River Monitoring 

The Oregon Department of Environmental Quality (DEQ) is responsible for keeping Oregon’s surface waters safe and healthy for a variety of uses such as drinking water, recreation, fish habitat and irrigation. To monitor trends in water quality, DEQ regularly collects water samples at over 150 sites on more than 50 rivers and streams across the state.

Most sites are visited every other month throughout the year, except for 6 Willamette River sites which are visited every month. Sites in SE Oregon are visited once a year in the fall. Water quality parameters that are measured include Alkalinity, BOD, Chlorophyll a, Specific Conductance, Dissolved Oxygen(DO), DO % Saturation , e. coli, Ammonia, Nitrate & Nitrite, pH, Pheophytin a, Dissolved Ortho-Phosphate, Total Phosphate, Total Solids, Temperature and Turbidity.

Some sites have been routinely monitored since the late 1940's. Long Term Large River Monitoring, also known as Ambient monitoring, is used to understand trends in Oregon's water quality over time, determine whether there is too much pollution in a water body, and set limits of how much pollution a water body can safely receive. Ambient monitoring data is also used to determine the Oregon Water Quality Index.

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