Oregon Water Quality Index Report for the Powder Basin 

Water Years 1986-1995

The Powder Basin is bounded on the north by the Wallowa Mountains, on the west by the Blue Mountains, on the south by the Burnt River Mountains, and on the east by the Snake River. The Powder and Burnt Rivers are the major tributaries in the basin. The basin is sparsely populated; most of the population is concentrated in Baker City. Land uses in the basin include logging, mining, grazing, confined animal feeding operations, irrigated and non-irrigated agriculture, urban/municipal uses, and recreation. Water quality data were routinely collected by the DEQ Laboratory and by the United States Bureau of Reclamation (USBR) in water years 1986-1995. On the average, Oregon Water Quality Index (OWQI) values at monitored sites in the basin range from very poor (Powder River at Highway 86) to good (Powder River at Campbell St. in Baker City) (Table 1).

Water quality is commonly impacted by the introduction of organic matter to streams. The presence of organic matter increases biochemical oxygen demand, which means less dissolved oxygen is available for aquatic life. The introduction of untreated animal or human waste increases the possibility of bacterial contamination of water, increasing the risk of infection to swimmers. Eutrophication is the process of enrichment of water with nutrients, mainly nitrogen and phosphorous compounds, which results in excessive growth of algae and nuisance aquatic plants. It increases the amount of organic matter in the water and also increases pollution as this matter grows and then decays. Employing the process of photosynthesis for growth, algae and aquatic plants consume carbon dioxide (thus raising pH) and produce an overabundance of oxygen. At night the algae and plants respire, depleting available dissolved oxygen. This results in large variations in water quality conditions that can be harmful to other aquatic life. While natural sources of nutrients can influence eutrophication, the introduction of nutrients strengthens the process. Sources of nutrients include wastewater treatment facility discharge and faulty septic systems, runoff from animal husbandry, fertilizer application, urban sources, and erosion. High water temperatures compound the decline in water quality by causing more oxygen to leave the water and by increasing the rate of eutrophication. Removal of streamside vegetation, among other factors, influences high stream temperature and, via erosion, increases sedimentation of streams.

Table 1. Seasonal Average OWQI Results for Powder Basin (WY 1986 - 1995)

Summer: June - September; FWS ( Fall, Winter, & Spring): October - May
Scores - Very Poor: 0-59, Poor: 60-79, Fair: 80-84,Good: 85-89, Excellent: 90-100

Powder Subbasin

The Powder River begins in the City of Sumpter at the convergence of McCully Fork and Cracker Creek. These tributaries drain a portion of the Blue Mountains, and the lands in the area are used for logging and mining. Historically, mines in the area were very productive. Evidence of past mining is seen in the dredge tailings lining the lower stretches of McCully Fork and Cracker Creek and covering the flood plain of the Powder River from Sumpter to Phillips Lake. The Powder River continues east from Phillips Lake and turns north around Elkhorn Ridge, flowing towards Baker City. The eastern slope of Elkhorn Ridge is protected for Baker City's water supply.

The uppermost site routinely monitored by DEQ Laboratory and USBR is on the Powder River at Campbell Street in Baker City. There are no significant point sources on the Powder River upstream of Baker City, so impacts to water quality at this monitoring site are due to non-point source pollution from logging, mining (dredge tailings), grazing, erosion, and field and urban runoff. High levels of total phosphates, fecal coliform, and biochemical oxygen demand impact water quality at this monitoring site. These high levels were seen during periods of heavy precipitation. This indicates the introduction of fecal and other organic materials to streams as a result of runoff and erosion. The high levels were also seen during extended dry periods, when lower flows cause pollutants to become more concentrated. On the average, OWQI scores for the Powder River at Campbell Street are good throughout the year (Table 1).

After flowing through Baker City, the Powder River receives treated discharge from the Baker City Wastewater Treatment Plant (WWTP) before meandering across the Baker Valley. Baker Valley is used for irrigated and nonirrigated agriculture, grazing, and confined animal feeding operations. The Powder River continues north, receiving drainage from Rock Creek, North Powder River, and Wolf Creek before bending around the Farley Hills near the City of North Powder. The North Powder River headwaters lie in the Blue Mountains and the Wallowa-Whitman National Forest. It descends the mountains and meets the Anthony Fork at the head of the North Powder Valley. This valley is used primarily for grazing and irrigated and nonirrigated agriculture. The City of North Powder WWTP discharges treated wastewater to the North Powder River near its mouth.

Soon after the Powder River changes direction to the southeast, towards the Snake River, it is impounded at Thief Valley Reservoir. This reservoir is eutrophic, meaning that sufficient nutrients are available to combine with warm temperatures and sunlight to produce algae blooms, some toxic, during the summer. Big Creek, which drains a portion of the Wallowa Mountains, joins Powder River upstream of the first of a series of diversion dams, marking the upstream boundary of the Lower Powder Valley. This valley is used primarily for grazing and irrigated and nonirrigated agriculture. DEQ Laboratory and USBR routinely monitor the Powder River at Highway 86, at the foot of the Lower Powder Valley. Like the upstream site in Baker City, high levels of total phosphates, fecal coliform, and biochemical oxygen demand impact water quality at this monitoring site. However, the intensity and frequency of the impacts are much greater. Moderately high levels of total solids were detected in conjunction with these impacts, indicating fine sediments and other suspended materials in the water. Eutrophication is active towards the end of summer when flow is low and water temperature is high, resulting in high dissolved oxygen supersaturation. On the average, OWQI scores at this site were very poor in the summer and poor in fall, winter, and spring (Table 1).

Burnt Subbasin

The Burnt Subbasin drains portions of the Blue and Burnt River Mountains. Burnt River forms from the convergence of the North, West, Middle, and South Forks of the Burnt River at Unity Reservoir. All four forks are situated within the Wallowa-Whitman National Forest and drain lands used for logging, grazing, and nonirrigated agriculture. The larger forks, North and South, also drain lands historically associated with mining. The North Fork Burnt River has its headwaters in the Greenhorn Range, and dredge tailings can be seen along the upper stretches of the river. USBR monitored Burnt River downstream of the Unity Dam. High levels of total phosphates and biochemical oxygen demand limit water quality at this site. This indicates the introduction of organic materials to the water. The phosphates may result from erosion or leaching of dredge tailings, or may be naturally occurring. The presence of phosphates, combined with warm temperatures in summer, fuels eutrophication and causes wide variation in dissolved oxygen levels and elevated pH. On the average, OWQI scores at this site were poor throughout the year (Table 1).

From its head at Unity Dam, Burnt River flows eastward towards its mouth at the Snake River, draining lands used for irrigated and nonirrigated agriculture, grazing, and calcium carbonate (lime) production. The City of Huntington WWTP discharges treated effluent to the Burnt River two miles from the river's mouth. USBR and DEQ Laboratory monitor the Burnt River downstream of Huntington. High levels of total phosphates, fecal coliform, and biochemical oxygen demand impact water quality at this monitoring site. Moderately high levels of total solids also impact water quality at this site. Sources of these impacts include erosion, runoff from agricultural operations, and possible releases of untreated effluent from the WWTP. High temperatures, pH, and dissolved oxygen supersaturation indicate that eutrophication is active during the summer. Water quality is worse at this site compared to the upstream site. Average OWQI values for the Burnt River downstream of Huntington are poor throughout the year (Table 1).

References

Johnson, D. M., et al., 1985. Atlas of Oregon Lakes. Oregon State University Press, Corvallis, Oregon.

Oregon Department of Environmental Quality, Water Quality Division, 1988. 1988 Oregon Statewide Assessment of Nonpoint Sources of Water Pollution. Portland, Oregon.

Oregon Department of Environmental Quality, Water Quality Division, 1988. Oregon's 1988 Water Quality Status Assessment Report (305 (b) Report). Portland, Oregon.

Oregon Department of Environmental Quality, Water Quality Division, 1990. Oregon's 1990 Water Quality Status Assessment Report (305 (b) Report). Portland, Oregon.

Oregon Department of Environmental Quality, Water Quality Division, 1992. Oregon's 1992 Water Quality Status Assessment Report (305 (b) Report). Portland, Oregon.

Oregon Department of Environmental Quality, Water Quality Division, 1994. Oregon's 1994 Water Quality Status Assessment Report (305 (b) Report). Portland, Oregon.

Written by Curtis Cude, Oregon Department of Environmental Quality, Laboratory Division