Bull Run Reservoir Number Two (Clackamas, Multnomah)
Reachcode: 17080001017571 | Area: 453.8 acres | Shoreline: 12.4 mi | View on Interactive Map
(From Atlas of Oregon Lakes, Johnson et al. 1985). Bull Run Reservoir No. 2, formed in 1961 with the completion of an earth and rockfill dam, is the newest of the two reservoirs on the Bull Run River. It lies at the western end of the Bull Run Reserve, a 214 square mile region that includes the Bull Run Watershed which provides a dependable supply of high quality water to the City of Portland and adjacent areas. The Bull Run Forest Reserve was created in 1892 by presidential proclamation, giving substance to the concept that undisturbed watersheds are critically important to the maintenance of a high quality water supply.
The Reserve remained largely in primitive condition until the mid-1950s, when tree harvesting and access roads were permitted in order to alleviate concerns about uncontrolled fires sweeping through the virgin Douglas fir and western hemlock forests. A hydroelectric power generation facility has been added to the reservoir by Portland General Electric, but the city of Portland continues to have exclusive rights to the watershed. Water is withdrawn just below the dam, is chlorinated, and delivered to conduits for transport to the City.
Water in Bull Run Reservoir #2 is of the same high quality as that in the upstream impoundment. Concentrations of major ions, alkalinity, and conductivity are all low and water transparency is very high. It is an oligotrophic water body, although an algal bloom was observed once shortly after construction. Maximum depth at the reservoir is over 100 feet and a distinct thermal stratification develops in summer. An occasional problem with turbidity in the water does occur, as discussed in the previous report on Bull Run Reservoir No. 1.