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How Is Water Quality Measured in the Umpqua Basin?

Monitoring involves a series of observations, measurements, or samples collected and analyzed over time. Many reasons exist for monitoring water quality. Monitoring can be used to identify areas where water quality standards are not being met and resources such as salmon and trout are being impaired. Monitoring can also be used to identify the sources and loads of pollutants that are causing these declines. Once the areas and causes of these water quality problems have been identified, monitoring can be used to measure the overall effectiveness of the water quality protection efforts and individual practices.

ODEQ assesses trends in the quality of the state's water by way of its Oregon Water Quality Index (OWQI). The OWQI analyzes a defined set of water quality variables and produces a score describing general water quality. These water quality variables include temperature, dissolved oxygen, pH, and bacteria, among several others. Water quality is monitored at a network of sites designed to provide representative statewide coverage. There are currently 144 monitoring sites in the state, of which nine are located in the Umpqua Basin.

Data from each of these monitoring sites is analyzed annually, with each site assessed for overall water quality and trends in water quality over a 10-year period. Water quality trends are analyzed and rated as significantly increasing, significantly decreasing, or with no significant change. Overall water quality is rated as excellent, good, fair, poor, or very poor.

The table below shows 10-year trends and overall water quality ratings for 132 sites statewide (those with sufficient data for trend analysis) as well as the nine sites for the Umpqua Basin. This data is from ODEQ's "Oregon Water Quality Index Summary Report, Water Years 1995-2004."

Area # Sites Overall Water Quality
Umpqua Basin 9 11% 11% 22% 44% 11%
Statewide 132 24% 25% 17% 19% 15%

E=excellent, G=good, F=fair, P=poor, VP=very poor 


Area # Sites 10-Year Water Quality Trend
Increasing Decreasing No Trend
Umpqua Basin 9 0% 11% 89%
Statewide 132 24% 10% 66%


Resource managers need monitoring data to improve practices and to better protect fish and fish habitat. The monitoring process and the data generated can also provide a valuable educational tool for a wide variety of user groups, such as wat rshed councils, school groups, researchers, and other stakeholders. The data collected through monitoring can be useful for developing plans to restore and protect a stream's biological capacity, as well as determining whether completed restoration projects achieved their intended goals.

Watershed councils, such as the Partnership for the Umpqua Rivers, and other local groups play a critical role in identifying the causes of decline in a stream's ability to support salmon and trout populations and other beneficial uses, as well as documenting results of restoration projects. To access water quality monitoring data from monitoring stations in the Umpqua Basin and the entire state, go to  ODEQ's water quality data webpage.