Study area
PROJECT CHIEF: Joseph F. Rinella
LOCATION: Klamath and Lake Counties
PROJECT EXTENT: Upper Klamath Basin, Oregon
TOTAL AREA IN SQUARE MILES: 3,800
COOPERATOR: Bureau of Reclamation
Upper Klamath Lake (map) is a large, shallow lake in southern Oregon. The lake is the source of the Klamath River, which flows through Northern California into the Pacific Ocean. The lake has probably been naturally eutrophic since before settlement of the basin by non-Native Americans (Bortleson and Fretwell, 1993, USGS Water-Resources Investigations Report 93-4087). 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 have become high enough to cause annual, extensive, nuisance-level blue-green algae blooms that result in degraded water quality. (Excessive blue-green algae production is an indicator of hypereutrophic conditions.)
The alga responsible for the blooms is Aphanizomenon flos-aquae, which was first detected in Upper Klamath Lake in the early 1930s and then became abundant by the end of that decade. Since the 1960s, A. flos-aquae has been by far the dominant algal species in the lake. In summer, blooms of A. flos-aquae turn the lake water an opaque green (photo) . The proliferation and subsequent die-off of the alga causes wide fluctuations in dissolved oxygen and pH; State standards for dissolved oxygen and pH are often violated.
In 1988, two formerly abundant Upper Klamath Lake fish species, the Lost River sucker and the shortnose sucker (Catostomidae), were placed on the Federal Endangered-Species list. The decline of sucker populations has been hypothesized to have been caused by degraded lake-water-quality conditions (Bortleson and Fretwell, 1993). Sucker die-offs have been common since the 1980s.
It is apparent that water-quality conditions in Upper Klamath Lake have changed since the early 20th century. The settlement of the Upper Klamath Basin by non-Native Americans beginning in the mid-1800s brought with it land-use changes that included wetland drainage, grazing, irrigation, and timber harvesting. An increase in sedimentation rate beginning at about that time (Eilers and others, 2001, Recent Paleolimnology of Upper Klamath Lake, Oregon, Report to the Bureau of Reclamation by J.C. Headwaters, Inc., Roseburg, Oregon) suggests that land-use changes in the tributary basins and land surrounding the lake are associated with the changes in water quality.
The most dramatic changes in the basin during the 20th century were the result of agricultural modifications. Since the 1930's, large areas of marsh surrounding the lake and bordering the Sprague River have been diked, ditched, and drained for agricultural use, leading to the decomposition of organic soils. Riparian vegetation has been degraded or completely eliminated. Regulation of the lake for irrigation purposes has caused lake-stage fluctuations to be both higher and lower than natural levels. At low levels the lake is more susceptible to wind-induced resuspension of bottom sediment. Lake flushing patterns have changed as a result of reservoir regulation and stream diversions. A hydrologic analysis is needed to better understand the effect and timing of nutrient loads from rivers.
OFR 95-285. Selected bibliography of water related research in the Upper Klamath Lake Basin, Oregon, by Dorie L. Brownell and Mia R. Rinallo. Abstract | Available online
OFR 95-414. Upper Klamath Basin nutrient-loading study - Estimate of wind-induced resuspension of bed sediments during periods of low lake elevation, by Antonius Laenen and Alex Le Tourneau. Abstract
WRIR 96-4079. Relation between selected water-quality variables and lake level in Upper Klamath and Agency Lakes, Oregon, 1996, by Tamara M. Wood, Gregory J. Fuhrer, and Jennifer L. Morace. Abstract | Available online
WRIR 97-4059. Nitrogen and phosphorus loading from drained wetlands adjacent to Upper Klamath and Agency Lakes, Oregon, By Daniel T. Snyder and Jennifer L. Morace. Abstract | Available online
WRIR 98-4198. Upper Klamath Lake Basin Nutrient-Loading Study--Assessment of Historic flows in the Williamson and Sprague Rivers, By John C. Risley and Antonius Laenen. Abstract | Available online
Contact: info-or@usgs.gov
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