Bull Run Lake (Clackamas, Multnomah)
Reachcode: 17080001017626 | Area: 434.1 acres | Shoreline: 4.7 mi | View on Interactive Map
(From Atlas of Oregon Lakes, Johnson et al. 1985). Bull Run Lake, located on the west slope of the northern Oregon Cascades, is one of the least visited yet most important lakes in Oregon. It lies at the head of the drainage basin of the Bull Run River, and is a vital part of the water supply for about a third of the population of the state, which includes much of the city of Portland and adjacent areas. The Bull Run watershed is located within the Bull Run Reserve, a protected region of 102 square miles. This water source is unique in the United States for the degree of protection afforded it, the directives governing its management, and the degree of public input provided for consideration in management planning. Most of the reserve land is owned and administered by the National Forest Service, while the city of Portland owns 3730 acres of timberland. The city owns and operates the storage reservoirs and water conveyance system within the reserve. (See reports on Bull Run Reservoirs No. 1 and No. 2 in this volume.) The lake was named for the river which flowed through a region where escaped cattle ran wild in early pioneer years. The Klickitat Indian word for the lake was Gohabedikt, meaning Loon Lake.
Seen by relatively few people, Bull Run Lake is one of the most beautiful water bodies in the Pacific Northwest, and lies in a basin formed by Pleistocene glaciation. It is a deep basin, surrounded on three sides by steep ridges with slopes of 30 to 60 percent. These ridges rise from the lake (-3175 feet above sea level) to a high point of 4654 feet at Hiyu Mountain. The origin of the natural dam on the west side of the lake is unclear. It has been described as a classic terminal moraine, impounding the waters of a glacial cirque. Certainly the basin is a cirque, but it is now apparent that the natural dam forming the lake consists of a series of flows of basaltic andesite, with a scattering of morainal material on top of the volcanic material. The material forming the dam is very porous and the outflowing stream seeps into the ground a short distance from the lake and emerges about one-half mile later to become the Bull Run River (Raymond 1983). In 1922 a concrete dam and spillway was constructed at the outlet to control discharge and to raise the water level about 20 feet. A number of small, steep streams supply surface inflow to the lake and direct precipitation (annual precipitation = 110 inches) accounts for a large percentage of the water supply. Despite the proximity to Mt. Hood, none of the water in Bull Run Lake or the Bull Run River comes from glaciers on the volcanic peak. Deep canyons of the West Fork of Hood River and the Sandy River lie between the Bull Run drainage basin and the Mt. Hood drainage.
Nearly a century of protection has permitted the preservation of the small Bull Run drainage basin in a natural state. The slopes are covered with a virgin conifer forest, with the exception of a few areas of bare talus slope and talus shrub communities. This elevation in the Cascades coincides with the transition zone between the true fir and hemlock vegetation associations, with some Douglas fir. In 1966 the 361-acre Bull Run Research Natural Area was established on the south and eastern slopes above the lake to provide continued protection and research opportunities in this natural area which is essentially free of any human disturbance.
As noted, access to Bull Run Lake is strictly controlled to minimize human contamination of the water; thus, the drainage basin is pristine and the water quality is excellent. Concentrations of chemical constituents are very low, although the water is not as dilute as in some other Cascade Mountain lakes that receive human use, specifically Big Lake and Waldo Lake. Conductivity and alkalinity are low, and transparency of the water is high. Moderate populations of diatoms develop in the lake, dominated by Cyclotella stelligera and Melosira distans. Thermal stratification develops in the water column with water as cold as 39 degrees Fahrenheit (4 degrees Celsius) below a depth of 75 feet at all times of the year. The low phosphorus and chlorophyl concentrations and the high water transparency indicate an oligotrophic state. A detailed paleolimnological study (Raymond 1983) indicates that chemical and biological conditions in Bull Run Lake today are similar to conditions existing over the past several thousand years. The sediment record provides evidence of temporary changes in limnological conditions in the lake resulting from volcanic activity at nearby Mt. Hood or Mt. St. Helens and from forest fires during periods of area-wide drought conditions. The sediment record also indicates that after such disturbances, the lake has always returned to. conditions similar to those seen at present.