U.S. Geological Survey Studies in the Klamath Basin, Oregon and California

The Klamath Basin

Upper Klamath Lake is a large, shallow lake in southern Oregon. The lake is the source of the Klamath River, which flows through California into the Pacific Ocean. The lake has probably been naturally eutrophic since before settlement of the basin by non-Native Americans. A eutrophic lake contains a high level of nutrients, which can result in occasional algal blooms, but generally such lakes can support diverse plant and animal communities. During the 20th century, however, Upper Klamath Lake has become hypereutrophic, which means that its nutrient levels are high enough to cause annual, extensive blue-green algae blooms that have occurred each summer since the 1930's. (Excessive blue-green algae production is an indicator of hypereutrophic conditions.)

Water-quality problems that coincide with the blooms and subsequent decay of dead algae include foul odors, pH of 8.5 and higher, dissolved oxygen concentrations that fluctuate from supersaturation to depletion, elevated ammonia concentrations, and occasionally extensive fish kills. The degraded water quality has been proposed as a contributing factor in the decline in populations of the shortnose sucker, Chasmistes brevirostris, and the Lost River sucker, Deltistes luxatus, both listed as Federally Endangered Species.

The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation, began studies in 1992 to determine possible causes for the change in trophic status of Upper Klamath Lake. Since that time, the areas of study have expanded to include groundwater, geomorphology, streamflow forecasting, and fish ecology. (See links at left.). The various studies have generated several publications, most of which can be accessed online.