Upper Klamath Lake (Klamath)

Reachcode: 18010203003572 | Area: 62129.9 acres | Shoreline: 169.4 mi | View on Interactive Map

(From Atlas of Oregon Lakes, Johnson et al. 1985). Upper Klamath Lake, with a surface area of 61,543 acres (over 70,000 acres including Agency Lake), is the largest freshwater lake in Oregon and one of the largest in the United States. It is a natural water body lying in the structural valley known as the Klamath Graben. Including Agency Lake and its connecting channel, it is about 25 miles long and ranges in width from 2.5 to 12.5 miles. It lies east of the Cascade Mountains at an elevation of 4139 feet. The water level is regulated by a low dam constructed in 1917 by the Bureau of Reclamation, which maintains the surface elevation between 4137 feet and 4147 feet. The drainage basin is about 3800 square miles, much of it a mountainous volcanic area covered with pumice deposits derived from the formation of the Crater Lake caldera. Elevations in the basin range from 4147 feet at the lake to over 9000 feet at some of the higher peaks in the Cascade Mountain Range to the west. The mountains create a rain shadow over much of the area, and precipitation varies from as little as 15 inches at lower elevations, to more than 60 inches at higher elevations. Consequently, vegetation also varies; the mountainous regions have forests of Douglas fir, ponderosa pine, lodgepole pine and true firs, while the open flatlands are associated with large pumice deposits occupied by grass-shrub communities. Large marshes exist throughout the drainage basin. The Sycan (995 acres) and Klamath Marshes (8121 acres) cover the basins of former Pleistocene lakes and extensive marsh areas surround much of the present Upper Klamath and Agency Lakes. Flora associated with the marsh area is a typical sedge-reed community. Since World War I, large sections of marsh have been reclaimed for agricultural use.

The major tributary of Upper Klamath Lake is the Williamson River, accounting for about 46 percent of the inflow to the lake. The origin of this river is a large spring, and it flows through pasture land before entering Klamath Marsh. The river flowing out of the marsh is a dark brown color due to very high dissolved aquatic humus concentrations. The Sprague River joins the Williamson River just prior to entering Upper Klamath Lake on the north shore. Wood River is the second largest tributary, and drains into Agency Lake and then into Upper Klamath Lake on the north shore. Other tributaries, mostly draining agricultural areas, also enter the lake. The outlet is the Link River flowing out of the south end of the lake into Lake Ewauna and into the Klamath River which eventually enters the Pacific Ocean in northern California.

Upper Klamath Lake fills a vital role in water-resource utilization in south central Oregon. Water from the lake is used for irrigation of reclaimed agricultural land; it is regulated to enhance power generation at the Pacific Power and Light projects on the Link River and farther downstream on the Klamath River at the John C. Boyle facility; also it is used extensively by waterfowl, the marshy habitat being an important stopover during fall and spring migrations on the Pacific flyway. Recreational use of Upper Klamath Lake has always been a major focus, particularly for fishing and boating. However, water-contact sports are discouraged by the poor water quality. Several resorts are located at various places around the lake, especially on the west side near the Lake of the Woods road, and there are numerous public campgrounds, picnic areas and boat launching sites. For the angler, rainbow trout are the major attraction and some very large fish have been caught. Most of the fishing is done along the western shore, from Pelican Bay south to Wocus Bay and most of it close to shore because of rough waters commonly encountered farther out in the lake. In addition to trout, warm-water species also thrive in Upper Klamath Lake. Fishing for trout is allowed all year in the southern part of the lake; the northern part, including Agency Lake, is open only during the normal summer trout season. Two genera of Cyprinidae, blue chub (Gila bicolor) and tui chub (Siphateles bicolor), constitute 90 percent of the fish population in the lake.

The maximum depth of Upper Klamath Lake is over 50 feet at several rather confined areas of deep water along the west shore. However, most of the lake is shallower than 20 feet. The concentrations of major ions are slightly above average, as is the conductivity. The concentration of phosphorus in the water is quite variable with the season, but is always high. The inflow to the lake from the Williamson River carries a high concentration of phosphorus derived from natural springs and from surface runoff. The sediment on the bottom of the lake is quite thick, is very rich in phosphorus and other nutrients, and is a significant source of nutrients. The most unusual aspect of the chemistry of the lake is the seasonal influx of dissolved organic matter (humic substances) derived from the Klamath Marsh through which the Williamson River passes on its way to Upper Klamath Lake.

Although situated in beautiful natural surroundings, there has never been much development on the shoreline of the lake because of the massive summer blooms of highly offensive blue-green algae. Severalstudies have indicated that the blooms are entirely natural and maintained by enormous supplies of nutrients contained in the bottom deposits and probably by additional supplies originating in the Klamath and Sycan Marshes and delivered to the lake via the Williamson River. The overwhelming dominant alga is Aphanizomenon flos-aquae, which is a blue-green alga that forms large colonies that resemble "grass clippings". It begins to appear throughout the lake in late spring, and continues to increase to very high densities (as high as 30,000 filaments per ml) by late summer. In early fall, nearly all of the Aphanizomenon die, and the decomposition of this large amount of biomass creates undesirable conditions such as dissolved oxygen depletion and strong unpleasant odors. The timing of the annual Aphanizomenon bloom (i.e., dates of appearance and decline) has been correlated with the flow of the Williamson River (Perdue et al 1982). Outflow from the humus-rich Klamath Marsh ceases each summer; during dry years the flow ceases earlier than during wet years. The Aphanizomenon in Upper Klamath Lake follows this same pattern; in dry years the bloom starts earlier than in wet years. No explanations were provided, but the strong correlation suggests an influence of the Williamson River upon Aphanizomenon in Upper Klamath Lake. The densities of Aphanizomenon vary from place to place in the lake; a few bays have very high densities, marshy areas tend to have lower densities, and winds may concentrate the algae near downwind shores. The phytoplankton samples in this survey in 1982 were collected near Eagle Point where the maximum depth is found; the phytoplankton densities were much lower here than in most other sections of the lake. Although only 206 filaments of Aphanizomenon per ml at Eagle Point were measured on 8/22/82, nearby Shoalwater Bay had an extremely high Aphanizomenon density, sufficient to thickly cover the water surface. In winter Cryptomonas erosa is most abundant, followed by Stephanodiscus astrea minutula during early spring. Other common species of phytoplankton include Gloeotrichia echinulata, Anabaena circinalis, Anacystis aeruginosa, Asterionella formosa and Melosira.

Other problems associated with this hypereutrophic lake are an overabundance of midges and dense beds of macrophytes. The midge larvae (Chironomus) grow in bottom sediments where the water is shallow, which is most of the lake. The adults swarm and create a serious nuisance to humans on and near the lake. Many shallow bays, particularly Pelican Bay, are covered with the macrophyte Potamogeton crispus; these aquatic weeds seriously deter boating traffic.

Upper Klamath Lake has come under study several times during the past few decades in the hope that solutions to these problems might be found. The most recent study was performed during 1981-1983, and was funded by EPA through the Clear Lakes Program (Klamath Consulting Service 1983). This EPA-funded study investigated several lake restoration ("manipulation") alternatives aimed at reducing the algal bloom and macrophyte problems, as well as addressing navigation problems resulting from low water levels. Three sections of the lake were identified as possible sites that may benefit from restoration technology. The southern part of the lake receives the largest amount of recreation, as it is nearer to the population center of the area. The major problem here is the inability of boats to navigate during low water periods, hence recreation and tourism suffer seriously. Howard Bay is another area that receives extensive recreational activity; dense algal blooms occurring here deter these activities. The third area receiving attention under the study was Pelican Bay, where extensive macrophyte growths (Potamogeton crispus) deter navigation and degrade water quality.

The primary restoration alternative proposed was to maintain the minimum lake level three feet higher than is presently maintained. This would greatly benefit the navigation problems in all areas of the lake, and an improvement in water quality would be likely. The study monitored water quality conditions for two years: 1981 was a drought year and the lake level was low, but 1982 was a wet year and higher lake levels existed. The water quality was better in 1982 with higher lake levels than in 1981 when the lake was shallower. To maintain a higher lake level, additional water supplies would be needed during summer; an off-stream storage project presently under consideration would meet this requirement. Other restoration alternatives are specific to the three sites mentioned above. These include dredging a channel in the south part of the lake, dredging either a 3000 acre area or a channel in Howard Bay, flushing Howard Bay in the event off-stream storage water becomes available in the future, and harvesting and/or screening the macrophyte beds in Pelican Bay.

It must be emphasized that Upper Klamath Lake is a naturally hypereutrophic lake, and that any restoration activity would only lessen the problems inherent in this lake and could not resolve or eliminate them. Nevertheless, restoration alternatives, although costly, may improve conditions in Upper Klamath Lake sufficiently to benefit water quality, recreation and navigation.


The list below includes results of zebra and quagga mussels surveys conducted by the Center for Lakes and Reservoirs and other agencies. The results "non-detect" and "results pending" indicate that surveys for zebra and quagga mussels were conducted, but none were detected or results are pending. For more details on zebra and quagga mussel monitoring, please visit the Online Mussel Monitoring Map.

Date Status/Species Source
Aug. 20, 2013 non detect Portland State University
July 10, 2013 non detect Portland State University
July 9, 2013 non detect Portland State University
July 24, 2012 non detect Portland State University
Aug. 1, 2008 non detect Portland State University

The list of plants below includes results of aquatic plant surveys conducted by the Center for Lakes and Reservoirs as well as aquatic invasive plant species detections that have been reported to iMap Invasives: an online, GIS-based invasive species reporting and querying tool.

Plants listed in the table below are categorized as native to Oregon, on the Oregon Department of Agriculture’s (ODA’s) Noxious Weed List, on the Federal Noxious Weed List, or non-native but not listed as noxious. Federal Noxious Weed List plants are plants determined by USDA to be serious threats to U.S. agriculture, irrigation, navigation, public health or the environment (7 C.F.R. 360.200). The ODA Noxious Weed categories are:

ODA Class A - weeds either unknown or with small enough infestations to make eradication or containment possible; targeted for eradication or intensive control.

ODA Class B - regionally abundant weeds (may have limited distribution in some counties); targeted for local/regional control on case-by-case basis.

Download the complete dataset as a CSV

Date Species Status Source
Aug. 15, 2012 Fontinalis antipyretica (antifever fontinalis moss) Native CLR
Aug. 15, 2012 Sagittaria sp. (arrowhead) Native CLR
Aug. 15, 2012 Utricularia vulgaris (common bladderwort) Native CLR
Aug. 15, 2012 Typha latifolia (common cat-tail) Native CLR
Aug. 15, 2012 Elodea canadensis (common elodea, Canadian waterweed) Native CLR
Aug. 15, 2012 Hippuris vulgaris (common mare's-tail) Native CLR
Aug. 15, 2012 Ceratophyllum demersum (Coontail; hornwort) Native CLR
Aug. 15, 2012 Potamogeton crispus (curly leaf pondweed) Non-native CLR
Aug. 15, 2012 Lemna sp. (duckweed) Native CLR
Aug. 15, 2012 Potamogeton natans (floating leaf pondweed) Native CLR
Aug. 15, 2012 Spirodela polyrrhiza (great duckweed) Native CLR
Aug. 15, 2012 Chara sp. (muskwort) Native CLR
Aug. 15, 2012 Eleocharis acicularis (needle spikerush) Native CLR
Aug. 15, 2012 Myriophyllum sibiricum (northern watermilfoil) Native CLR
Aug. 15, 2012 Potamogeton sp. (pondweed) Native CLR
Aug. 15, 2012 Potamogeton richardsonii (Richardson's pondweed) Native CLR
Aug. 15, 2012 Stuckenia pectinata (sago pondweed) Native CLR
Aug. 15, 2012 Potamogeton pusillus (slender pondweed) Native CLR
Aug. 15, 2012 Schoenoplectus tabernaemontani (softstem bulrush) Native CLR
Aug. 15, 2012 Lemna trisulca (star duckweed) Native CLR
Aug. 15, 2012 Ranunculus aquatilis (water-buttercup) Native CLR
Aug. 15, 2012 Nuphar polysepala (yellow water-lily) Native CLR
Aug. 15, 1981 Lythrum salicaria (purple loosestrife) Non-native ODA Class B IMAP
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