- Malheur County)
(From Atlas of Oregon Lakes, Johnson et al. 1985). Beulah Reservoir (formerly known as Agency Valley Reservoir) is a large impoundment in the Malheur River system in northeast Oregon. It was formed by the 121-foot high Agency Valley Dam, which was built in 1935 to impound the flow of the North Fork of the Malheur River near Beulah, Oregon. At full pool the reservoir covers about 2000 acres and has a storage capacity of over 60,000 acre-feet. It is one of the major components of the Bureau of Reclamation's Vale Project, an irrigated area of about 35,000 acres located along the Malheur River and Willow Creek, surrounding the town of Vale. The project stores water in Warm Springs Reservoir, Beulah Reservoir, and Bully Creek Reservoir. The stored water in Warm Springs and Beulah Reservoirs, together with natural streamflow, is diverted from the Malheur River by the Harper Diversion Dam to the Vale Main Canal.
Lands now included in the Vale Project were irrigated as early as 1881 by settlers who built small distribution systems that diverted water directly from the Malheur River. Independent ditch companies were formed as irrigated acreages increased, and by the 1920s more than 63,000 acres were being irrigated. At the request of local interests, the Bureau of Reclamation began investigations in 1925 to determine the feasibility of developing a project in the area. In 1926 the Bureau purchased a half interest in the Warm Springs Dam and Reservoir. The Harper Diversion Dam was completed in 1929, the Vale Main Canal in 1935, Agency Valley Dam and Beulah Reservoir also in 1935, and the Bully Creek Dam and Reservoir in 1963. The project is operated and maintained by the Vale Oregon Irrigation District. In addition to the transformation of thousands of acres of sagebrush and ranchland into productive farmland, the three reservoirs are operated on a coordinated forecast basis for flood control. Of the three, Beulah Reservoir provides the best opportunities for recreation. There are campgrounds and facilities for launching and mooring boats, but no camping improvements. The reservoir is open to angling all year, and has provided good sport. It has been treated for rough fish several times, and then restocked with rainbow trout. Dolly Varden trout and whitefish are also in the reservoir. Because of the broad oval shape of the reservoir and the absence of obstructions in the water, powerboating and water-skiing are popular recreational pursuits.
Beulah Reservoir is nestled in Agency Valley, almost filling the small triangular valley. It receives drainage from an area of 440 square miles, most of this from the North Fork of the Malheur River. The upper part of the basin is a forested portion of the Blue Mountains within the Malheur National Forest. At lower elevations is rangeland, some of it privately owned, but most of it under the jurisdiction of the Bureau of Land Management. The shoreline of the reservoir is also federal land.
The North Fork of the Malheur River has excellent water quality, and as a result Beulah Reservoir has better water quality than most eastern Oregon reservoirs. This condition is further encouraged by the greater depth in the reservoir as compared to others. Major ion concentrations are about average for eastern Oregon reservoirs; however, the total phosphorus concentration is somewhat higher (0.072 mg/1). The reservoir was thermally stratified when sampled on 6/24/82. At this time, only a slight depletion of hypolimnetic dissolved oxygen was found; however, later in the summer it would be expected to be greater. Although water transparency and chlorophyl concentration indicate mesotrophic conditions on the sampling date, these would probably shift to eutrophic conditions later in the summer. Overall, Beulah Reservoir is classified as eutrophic, but at the low end.