Malheur Reservoir (Malheur)

Reachcode: 17050119001844 | Area: 319.9 acres | Shoreline: 5.2 mi | View on Interactive Map

(From Atlas of Oregon Lakes, Johnson et al. 1985)  Malheur Reservoir (also known as Willow Creek Reservoir) is an irrigation and flood control project located on Willow Creek in northeastern Oregon. It was built in the late 1930s by the Orchard Irrigation District and provides water for the irrigation of about 2300 acres of agricultural land downstream on Willow Creek. Inflow to the reservoir is controlled by the natural climatic regime and by irrigation demand along Willow Creek upstream. The Willow Creek drainage basin above the reservoir is a semi-arid rangeland. Most of it is privately owned with scattered pieces of federal land administered by the Bureau of Land Management. About 80 percent of the shoreline of the reservoir is privately owned.

Recreational use of the reservoir is relatively light. There is some water-skiing, but most visitors are fishermen. In 1963 the reservoir, along with most of the Malheur River system, was treated for rough fish. It was then restocked with rainbow trout and angling has been relatively good since that time, although an over abundance of rough fish has been reported by the Oregon Department of Fish and Wildlife in recent years. There are two boat ramps available for use, one of them paved, and sanitary facilities built by a sportsman's club. However, there are no facilities for overnight camping.

The bathymetric data presented here represent the reservoir at full pool, a volume of nearly 49,000 acre feet and a surface area of about 1300 acres. However, for several years storage has been limited to 20,000 acre-feet, at a water surface elevation of about 20 feet below full pool, due to instability of the dam. For much of the year, the water level is even lower because of withdrawals for irrigation. Water quality is typical of eastern Oregon reservoirs in a semi-arid basin. There are extremely high concentrations of major ions (conductivity 447 umhos/cm and total phosphorus 0.184 mg/1), probably derived from non-point sources within the drainage basin. The phosphorus supports abundant phytoplankton growth; the phytoplankton, in turn, decrease the water transparency and also reduce the dissolved oxygen concentration in the bottom waters. In sum, Malheur Reservoir is naturally eutrophic.

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
July 18, 2012 non detect Portland State University
No plant data available.