USGS Uses State-of-the-Art Science to Estimate Nutrient and Suspended-Sediment Loads in the Klamath Basin

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USGS uses state-of-the-art science techniques to estimate phosphorus and suspended-sediment loads to Upper Klamath Lake in the Klamath Basin.

USGS Streamgage on the Williamson River
A U.S. Geological Survey hydrologist collects a water sample from the Williamson River below Chiloquin, Oregon. The sample was analyzed as part of a water-quality study the USGS conducted in cooperation with the U.S. Bureau of Reclamation and the Klamath Tribes.(Credit: Chauncey Anderson, USGS. Public domain.)

PORTLAND, Ore. — The U.S. Geological Survey has employed state-of-the-art science techniques to estimate phosphorus and suspended-sediment loads to Upper Klamath Lake in the Klamath Basin. Large algal blooms are attributed to high phosphorus concentrations in the lake during the summer causing numerous water-quality problems. The blooms are considered a contributor to survival problems for the endangered Lost River and shortnose suckers, which are culturally significant fish for the Klamath Tribes located near the lake.

The proof-of-concept effort shows continuous monitoring data can be used as surrogates to successfully estimate loads of phosphorus and sediment on monthly, daily and hourly time scales in this basin. “Understanding nutrient load dynamics that affect algal growth and decay, as well as water quality in Upper Klamath Lake, is crucial for management of the endangered sucker populations,” said Liam Schenk, USGS hydrologist leading the study.

The study, conducted in cooperation with the Bureau of Reclamation, Klamath Basin Area Office and the Klamath Tribes, uses continuously measured data related to the scattering of light from particles suspended in the water. These data are then combined with streamflow data and statistical methods to calculate concentrations and loads of sediment and phosphorus for the two main tributaries to Upper Klamath Lake, the Wood and Williamson rivers. Suspended sediment is an important contributing factor to phosphorus loading because it acts as a transport mechanism for phosphorus from the upper watersheds to the lake. Results from this study highlight the usefulness of surrogate techniques to assess loading to the lake and the ability to report loads and model uncertainties in near real-time. The Oregon Real-time Water Quality page shows a graph with estimated suspended sediment concentrations on the Williamson River computed using this technique.

A 2002 Clean Water Act “total maximum daily load” standard for Upper Klamath Lake targeted a 40 percent reduction in external total-phosphorus loads to reduce the dense algal blooms that occur during the summer and fall months. Near real-time monitoring of total phosphorus and suspended sediment on the two main tributaries using these techniques will determine whether the targeted reductions are being reached through the combined effect of restoration projects in the upper Klamath Basin. Long-term datasets will be necessary to assess the trends in nutrient and sediment reductions over time. The application of surrogate techniques described in this report provides a cost-effective tool to measure these trends.

Results of the study are available in U.S. Geological Survey Scientific Investigations Report 2016-5167.