Scientific Investigations Report 2006–5209
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5209
Upper Klamath Lake (fig. 1) is located in southern Oregon; about 25 km north of the California-Oregon border and 18 km east of the crest of the Cascade Range. It is a large, relatively shallow lake with a surface area of 232 km2 and an average depth of 2.8 m at full pool. Most of the lake (92 percent) is shallower than 4 m, with the exception of a narrow trench running parallel to Eagle Ridge, on the lake’s western shore. This trench contains the deepest waters of the lake, approaching 15 m. Upper Klamath Lake is located in the Klamath Graben structural valley, and much of its 9,415 km2 drainage basin is composed of phosphorus-rich volcanically derived soils. The largest single contributor of inflow to the lake is the Williamson River, which constitutes about 46 percent of the lake’s incoming water and enters the lake near its northern end (Johnson and others, 1985). Agency Lake, just north of Upper Klamath Lake and connected to it by a narrow channel, has 37 km2 of surface area and an average depth of 2.2 m, and is for the most part distinct from Upper Klamath Lake hydrologically and in terms of water quality. Upper Klamath Lake was historically eutrophic, but over the past several decades has experienced nuisance blooms of the blue-green alga Aphanizomenon flos-aquae (AFA) during the summer and autumn, and can now be characterized as hypereutrophic.
Upper Klamath Lake is a natural water body, but lake surface elevations have been regulated since 1921, when Link River Dam was completed at the southern outlet of the lake. The dam was built, and is currently operated, by the Bureau of Reclamation, and Upper Klamath Lake is now the principal water source for the Klamath Project—an irrigation system developed to supply water to 970 km2 of farm and ranch land in and around the Upper Klamath Basin. During the summer months, water is diverted upstream of the lake for agricultural use, water is diverted downstream to supply the irrigators of the Klamath Project, water is sent downstream through the Link River to meet the flow requirements of the National Marine Fisheries Service for Klamath River coho salmon, and water is lost from the lake through evaporation. As a result, the lake level declines by about 1 m between June 1 and September 1. Lake elevations during the 3 study years were 1262.71, 1262.79, and 1262.64 m on June 1 in 2002, 2003, and 2004, respectively. On September 1, the elevations were 1261.44, 1261.76, and 1261.72 m in 2002, 2003, and 2004, respectively (on the basis of data for U.S. Geological Survey (USGS) site identification No. 11507001, which is a weighted average of three gages located around the lake).
Severe water-quality problems in Upper Klamath Lake have led to critical fishery concerns for the region, including the listing of Lost River and shortnose suckers as endangered in 1988. The lake’s algal community has shifted to a monoculture of AFA, massive blooms of which have been directly related to episodes of poor water quality. The growth and decomposition of dense algal blooms in the lake frequently cause extreme water quality conditions characterized by high pH (9–10), widely variable dissolved oxygen (anoxic to supersaturated), and high ammonia concentrations (greater than 0.5 mg/L, un-ionized).
In April 2001, the U.S. Fish and Wildlife Service (USFWS) released a Biological Opinion regarding the endangered suckers in Upper Klamath Lake. As part of that document, the USFWS provided several alternatives to allow for the continued operation of the Klamath Project. One of those alternatives was for the Bureau of Reclamation (Reclamation) to develop a study plan to better determine the role of “water quality refuge” areas in adult sucker survival in Upper Klamath Lake. This led Reclamation and U.S. Geological Survey (USGS) to enter into a cooperative agreement, the primary objective of which was to tag and track with radio telemetry a representative sample of the endangered suckers in the lake while simultaneously monitoring water quality. Water quality was monitored primarily through a network of multiparameter water quality instrumentation. The network was designed with the objective of being able to provide a “map” of water quality at any point in time, onto which the fish tracking information could be overlaid. Such a map would provide information about water quality not only where fish were located, but also where fish were not located, and would allow robust statistical tests of fish movement in response to water-quality conditions. The study area was limited to roughly the northern one-third of Upper Klamath Lake, largely because a previous tracking study done by Reclamation had indicated that the endangered suckers were located primarily in this area of the lake. The tracking data collected during this study has borne out that assumption.
The purpose of this report is to present the water quality information collected during the 3 years of the tracking study, along with a discussion of what has been learned about the factors determining water quality in Upper Klamath Lake. The results of the fish tracking in a water-quality context have been presented elsewhere (B.J. Adams, U.S. Geological Survey, unpub. data, 2005), but the wealth of information provided by the monitoring done in support of the tracking study, much of which went well beyond the original objectives, merits its own report.
U.S.
Department of the Interior | U.S. Geological
Survey
Persistent URL: https://pubs.water.usgs.gov/sir20065209
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