Lake Simtustus (Jefferson)

Reachcode: 17070306011851 | Area: 552.4 acres | Shoreline: 19.7 mi | View on Interactive Map

(From Atlas of Oregon Lakes, Johnson et al. 1985)  Lake Simtustus, also known commonly as Pelton Reservoir, is a large power-generating reservoir on the mainstem of the Deschutes River. It is located immediately downstream from Lake Billy Chinook. Pelton Dam was the first high dam on the river, built in 1958 by Portland General Electric. It is a 200-foot high, concrete arch structure. With the subsequent construction of Round Butte Dam, Lake Simtustus serves also as a reregulating reservoir, or surge basin, to handle releases from Lake Billy Chinook. The Warm Springs Indians chose the name Simtustus to honor a warrior of the tribe who served as a scout for the U. S. army in the 1867-68 campaign against the Paiutes.

Lake Simtustus is a long, narrow impoundment, about eight miles long and no more than one-quarter mile wide at any point. The contributing drainage basin includes the entire Deschutes River basin above this point, a mostly semi-arid rangeland with forested mountains in the headwater area. Surroundings are mostly steep canyon walls, with some more level sagebrush-grass grazing areas. Direct inflow to the reservoir, other than that from Lake Billy Chinook, is from an area of about 320 square miles via intermittent streams; Willow Creek and Seekseequa Creek are the major streams. The Warm Springs Reservation adjoins the lake on the west side and access is restricted. Federal land administered by the Bureau of Land Management comprises the eastern shoreline. The power company maintains a public campground and picnic area just above the dam. There are also a marina and boat launching ramps, and summer  use for fishing and boating is fairly heavy. A variety of trout are caught; also present are bass, bluegills, crappies, and catfish. A license from the Warm Springs Tribe is required to fish, although state fishing regulations apply.

Lake Simtustus is deep enough (average depth = 53 feet) to develop a noticeable temperature stratification during the summer. The concentrations of major ions are fairly high, and other chemical characteristics are very similar to the water of Lake Billy Chinook upstream. Although Billy Chinook traps much of the sediment from the extensive drainage basin, water transparency in Lake Simtustus is also limited.  Some of the fine sediment remains in suspension, and phytoplankton are abundant. Light blooms of blue-green algae (Aphanizomenon flos-aquae with some Gloeotrichia echinulata) are common and to be expected in a warm lake with a mud-bottom and sufficient sodium. The concentration of phosphorus is high and stimulates phytoplankton growth. Oxygen is sometimes moderately depleted in the deeper water. The overall character of the reservoir is eutrophic. However, there is very little growth of macrophytes around the lake, probably due to fluctuations in the water level.

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. 9, 2010 non detect Portland State University
Aug. 9, 2010 results pending Portland State University
No plant data available.