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Continuous Monitoring of Water Quality on the Boise and Snake Rivers


USGS technicians installing equipment on a bridge pier.
USGS technicians installing equipment
on a bridge pier, photo by USGS

The U.S. Environmental Protection Agency (EPA) has established water-quality standards for the Snake River to protect its designated beneficial uses. However, interactions among water-quality parameters that may affect beneficial uses are unknown. Also unknown is the significance of Boise River contributions to water quality in the Snake River. To assess these unknowns, the USGS and several cities along the Boise River partnered to develop a continuous monitoring program for the Boise and Snake Rivers.

How the USGS Helps

To understand the complex relations among nutrient loads, algae growth, and water-quality parameters in the Boise and Snake Rivers, it is important to study many aspects of these rivers. The USGS is operating a monitoring program that combines high-frequency automated sampling with routine site visits and manual sample collection.

Continuous water-quality monitors

Commercial multiparameter water-quality monitors have been installed at three locations—Parma, ID; Nyssa, OR; and Adrian, OR—on the Boise and Snake Rivers. This equipment measures temperature, pH, dissolved oxygen, specific conductance, turbidity, and chlorophyll-a fluorescence every 15 minutes.

Nutrient and chlorophyll-a sampling

During site visits, water samples are collected and analyzed for chlorophyll-a, dissolved orthophosphate, total phosphorus, dissolved ammonia, dissolved nitrite-plus-nitrite, and total nitrogen. Also, an automatic sampler has been reactivated at the Parma, ID site to collect water samples at 49-hour intervals; the samples are analyzed for total nitrogen and total phosphorus.

Streamflow measurement

Streamgages are operated at all three sites. Manual streamflow measurements are made approximately every 6 weeks to develop ratings that are used to compute streamflow on a continuous basis.

DH-95 water-quality sampler and bridge crane on the Snake River near Adrian
DH-95 water-quality sampler and bridge crane on the Snake River near Adrian, photo by USGS
Multiparameter water-quality monitor with individual instruments labeled
Multiparameter water-quality monitor with individual instruments labeled, photo by USGS


Wood, M.S. and Etheridge, A.B., 2011, Water-quality conditions near the confluence of the Snake and Boise Rivers, Canyon County, Idaho: U.S. Geological Survey Scientific Investigations Report 2011–5217, 70 p.

Water-quality relations on the Snake and lower Boise Rivers: 20th Annual Idaho Department of Environmental Quality Water Quality Workshop, February 2-4, 2010—presentation (PDF, 1.5 MB)

Assessment of the cross-sectional variability of water-quality parameters in the Snake River as a result of measurement Location—poster (PDF, 46 MB)

Diel fluctuations in nutrients and continuously-monitored parameters in two Idaho rivers—poster (PDF, 850 KB)