Oregon Water Quality Index Report for the Malheur and Owyhee Basins

Water Years 1986-1995

The Malheur and Owyhee Basins have similar geology, climate, land use patterns, and water quality impairment. Both basins drain desert mountains and semi-arid uplands used for grazing. The lower northeastern corners of both basins are crossed by irrigation canals, siphons, and ditches and drain to the Snake River. The confluence of the Malheur, Owyhee, Payette, Boise, and Snake Rivers in this relatively small area have caused a large flood plain to form over the millennia. The nutrient-rich sediments that were deposited in this flood plain support intense agricultural activities. Row crops such as onions, potatoes, sugar beets and corn as well as hay, grain, and pasture are produced. Confined animal feeding operations (CAFOs) and food processing operations also support the local economy and impact water quality.

Impacts to surface water quality are discussed in detail below, but it is important to note that groundwater quality (and hence drinking water quality in many locations) has also been impacted by agricultural practices. 115,000 acres of northern Malheur County, including portions of the Lower Malheur, Bully Creek, Willow Creek, and Lower Owyhee Subbasins, were designated as a Groundwater Management Area (GWMA) in accordance with Oregon's Groundwater Protection act of 1989. The shallow sand and gravel alluvial aquifer, formed by flood plain sediment deposits, receives a large portion of its recharge from irrigation water and canal leakage. Irrigation water percolating through the soil leaches nitrates and pesticides into the groundwater. A 1990 groundwater study confirmed widespread contamination of this aquifer with nitrates (at levels above the drinking water standard) and the herbicide Dacthal (at levels below the health advisory level). Irrigation methods and fertilizer application practices have been identified as the main sources of contamination. This irrigation water also returns to drainage ditches and eventually to the area's streams. An action plan has been developed to address the contamination issues and is being implemented in the area. The agricultural community is working to voluntarily implement Best Management Practices to protect groundwater quality throughout most of the GWMA.

Surface 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.

The United States Bureau of Reclamation monitored water quality in the Malheur and Owyhee Basins under contract for the Oregon Department of Environmental Quality. Monitoring data for water years 1986-1995 were analyzed for this report.

Malheur Basin

Malheur Basin is comprised of four subbasins, including the Upper Malheur, Lower Malheur, Bully, and Willow Subbasins. The Malheur River originates at the confluence of Big Creek and Lake Creek, which drain the southern Strawberry Mountain Wilderness. The Malheur River flows southeasterly for seventy-one miles and is impounded at Warm Springs Reservoir before meeting the South Fork Malheur River and turning north. Twenty-three miles downstream the Malheur River meets the North Fork Malheur River in Juntura Valley. This confluence marks the boundary between Upper and Lower Malheur Subbasins. Land use in the Upper Malheur Subbasin is predominantly range, although some irrigated agriculture. The Malheur River flows northeasterly for ninety-six miles before meeting the Snake River.

The most upstream monitoring site in the basin is thirty miles downstream from the confluence with the North Fork Malheur River, where Highway 20 crosses the Malheur River near Namorf. This site is one mile downstream of the first major diversion from the Malheur River, into the Vale Oregon Canal. High levels of total phosphates and moderately high levels of biochemical oxygen demand occasionally impact water quality at this site. These impacts occur throughout the year, but occur more frequently during the summer. This is due to irrigation returns to the river. High temperatures impact water quality during the summer as expected when flows drop and solar radiation increases. Active eutrophication is evidenced by high pH and high dissolved oxygen supersaturation, although these events were relatively infrequent. On the average, OWQI scores for the Malheur River downstream of Namorf are very poor in the summer and poor during the fall, winter, and spring (Table 1). Conditions at this site, although poor, represent the best conditions of the monitored sites in the basin. As the river moves downstream, the number of diversions for irrigation increase as do the number of irrigation returns to the river. These irrigation returns deliver relatively warm water that contains residual fertilizers, pesticides, and sediment to the Malheur River and its tributaries. As a result, water quality deteriorates in the river as it moves downstream (Table 1). As previously mentioned, local farmers are voluntarily implementing Best Management Practices to protect groundwater quality in the area. These practices will likely serve to protect surface water quality in the long run as well.

From Namorf, the Malheur River flows eighteen miles through Harper Valley before reaching the next monitoring site in Little Valley. Total phosphate and biochemical oxygen demand levels have increased in frequency and intensity, compared to the site at Namorf. High pH levels and wide swings in dissolved oxygen concentration indicate frequent eutrophication activity. High concentrations of fecal coliform impact water quality at this site. Location of feedlots (on or too close to waterways or in areas that periodically flood) and improper disposal of animal wastes are the major sources of high fecal coliform concentrations in the Malheur Basin. The effects of these water quality impacts are more severe in the summer when flow is low and water temperature is warm. These conditions cause the pollutant concentrations to increase as less water is available for dilution. On the average, OWQI scores for the Malheur River at Little Valley are very poor throughout the year, though conditions are better during the fall, winter, and spring (Table 1).

Table 1. Seasonal Average OWQI Results for Malheur 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

Bully Creek and Subbasin drain grazing and agricultural lands in northern central Malheur Basin. The lower stretch, downstream of Bully Creek Reservoir, flows into the Vale Valley and meets the Malheur River at the western (upstream) edge of Vale. Bully Creek is monitored at Highway 20, two miles upstream of Vale. Again, water quality is impacted by high levels of total phosphates, biochemical oxygen demand, and fecal coliform. High levels of ammonia and nitrate nitrogen were detected during various seasons, probably caused by excessive loss of fertilizers and the breakdown of animal waste washed into the creek. Low dissolved oxygen concentrations were detected during various seasons, due to the large amount of organic matter in the water. Warm temperatures and high pH values were occasionally detected, indicating eutrophication in Bully Creek. Moderately high levels of total solids were frequently detected at this site, in Willow Creek, and at the lower two Malheur River sites. The soils in the lower Malheur Basin are fine-grained flood plain deposits, prone to erosion. Highest sediment loss occurs during high runoff conditions, and is aggravated in some areas by livestock and poor farming practices. Impacts to water quality at this site are most likely due to land use in Vale Valley. On the average, OWQI scores at this site were very poor throughout the year (Table 1). Bully Creek had the ninth worst water quality of all sites throughout the state monitored by DEQ Laboratory and USBR for these basin reports.

USBR monitored the Malheur River at Highway 20 at the eastern (downstream) end of Vale. This site is downstream of the confluence with Bully Creek. Water quality results at this site reflect the cumulative effects of Bully Creek, the Malheur River itself (see conditions at Little Valley), and irrigation returns to the river in the Vale Valley. Comparing results with the monitoring sites upstream on the Malheur River finds that water quality impacts have increased again in frequency and intensity. Still higher levels of total phosphates, biochemical oxygen demand, and fecal coliform regularly impact water quality at this site. Like Bully Creek, high levels of ammonia and nitrate nitrogen and moderately high levels of total solids impact water quality in the Malheur River at Vale. Water quality at this site is slightly worse than the Bully Creek site during the summer. Due to its larger capacity, the Malheur River is more capable of recovering after the irrigation season. However, this recovery is not enough and average OWQI scores remain in the very poor category throughout the year (Table 1). Malheur River at Vale had the seventh worst water quality of all sites throughout the state monitored by DEQ Laboratory and USBR for these basin reports. Either more favorable conditions or the institution of Best Management Practices (BMPs) in parts of Vale Valley led to a significant, in terms of statistical confidence, though very slight increase in water quality in the Malheur River at Vale (Figure 1). One can conclude only that water quality was not getting worse between water years 1986 and 1995. If the BMPs in place continue to be implemented and more become instituted, water quality should continue to improve.

Figure 1. Trend Analysis Results for the Malheur River at HWY 20 (Vale)

Willow Creek and Subbasin drain range and irrigated agricultural lands in the northeastern portion of the Malheur Basin. Below Malheur Reservoir, the lower stretch of Willow Creek runs through the long Willow Creek Valley, used for irrigated agriculture. Willow Creek is monitored at Vale, at which point the creek amounts to little more than a drainage ditch. Water quality is severely impacted by high levels of total phosphates, ammonia and nitrate nitrogen, fecal coliform, total solids, and biochemical oxygen demand. All of these are due to the introduction of fertilizers, animal wastes, sediment, and other organic waste either directly to the creek or via irrigation returns. Moderately high pH values were seen during winter and spring months in conjunction with high run-off. OWQI values reached greater than thirty only twice during the ten year monitoring period. Willow Creek at Vale has very poor water quality throughout the year (Table 1). Willow Creek had the fifth worst water quality of all sites throughout the state monitored by DEQ Laboratory and USBR for these basin reports.

The Malheur River continues northeast from Vale and passes through the most heavily irrigated and cultivated lands in the basin before entering the Snake River north of Ontario. The Malheur River is monitored at Highway 30, one-half mile from the mouth of the river. Water quality impacts at this site are more intense and more frequent than at any other Malheur River site. Results reflect cumulative effects of upstream water quality (see conditions at the Vale site), Willow Creek, and irrigation returns. Water quality is severely impacted by high levels of total phosphates, ammonia and nitrate nitrogen, fecal coliform, total solids, and biochemical oxygen demand. Warm water temperatures, moderately high pH values, and wide variations in dissolved oxygen concentration indicate eutrophication activity in this stretch of the Malheur River. OWQI values reached greater than thirty only three times during the ten year monitoring period. Malheur River at Highway 30 has very poor water quality throughout the year (Table 1). This site had the second worst water quality of all sites throughout the state monitored by DEQ Laboratory and USBR for these basin reports.

Owyhee Basin

The land area of Owyhee Basin is significantly larger than the Malheur Basin, but the area of land suitable for agriculture is smaller. The largest part of the basin is used as rangeland. The Owyhee River and its tributaries drain portions of Idaho and Nevada as well as the southeastern corner of Oregon. The topography of the basin is marked by desert mountains, deep canyons, lava beds and craters. The Owyhee River is impounded from river miles seventy to twenty-nine at Lake Owyhee. Water is siphoned from Lake Owyhee and distributed as far north as Lower Dead Ox Flat on the Snake River, twenty-three miles downstream of the mouth of the Malheur River. From Lake Owyhee, the Owyhee River flows through a last stretch of canyon before reaching the Owyhee Bench. The bench is part of the larger flood plain and its soil shares the characteristics of those found in the lower Malheur Basin. Land use in the lower Owyhee Basin is the same as the lower Malheur Basin, namely irrigated agriculture and confined animal feeding operations. Impacts to water quality are at a smaller scale, due to the smaller amount of available land for these uses.

The upstream site monitored by USBR is the Owyhee River downstream of the Owyhee Dam. Results from monitoring at this site represent the cumulative effect of all impacts to water quality upstream of the dam. These impacts include grazing and natural conditions. Results from this site also serve as a background to compare to water quality near the mouth of the river. High pH values and wide variation in dissolved oxygen concentrations detected at this site indicate that eutrophication is active. The Atlas of Oregon Lakes identified Lake Owyhee as eutrophic with high levels of phosphorous entering the lake from the upper watershed. This explains the moderately high levels of total phosphates detected downstream of the dam. Moderately high levels of biochemical oxygen demand and ammonia and nitrate nitrogen were also detected at this site. On the average, OWQI scores for this upstream site are good throughout the year (Table 2). Unfortunately, water quality conditions in the upper water shed are deteriorating. A significant decrease in water quality between water years 1986-1995 was detected (Figure 2).

Figure 2. Trend Analysis Results for the Owyhee River downstream of Owyhee Dam

The downstream site monitored by USBR was on the Owyhee River at Highway 201. Results from monitoring at this site indicate the influence of irrigated agriculture and CAFOs on water quality in the Owyhee River. High concentrations of total phosphates and biochemical oxygen demand were detected and indicate a combination of high background levels of phosphorous and the introduction of fertilizers and organic waste via irrigation returns. High levels of ammonia and nitrate nitrogen were detected during various seasons, probably caused by excessive loss of fertilizers and the breakdown of animal waste washed into the creek. Location of feedlots (on or too close to waterways or in areas that periodically flood) and improper disposal of animal wastes are the major sources of high fecal coliform concentrations detected in the lower Owyhee Basin. Like the soils in the lower Malheur Basin, soils in the lower Owyhee Basin are fine-grained flood plain deposits, prone to erosion. Highest sediment loss occurs during high runoff conditions, and is aggravated in some areas by livestock and poor farming practices. Warm temperatures combined with relatively high pH values and wide variations in dissolved oxygen concentration indicate that eutrophication is active in the lower stretch of the river. Water quality has significantly decreased from upstream to downstream. On the average, OWQI scores for the Owyhee River at Highway 201 are very poor throughout the year (Table 2). As previously mentioned, local farmers are voluntarily implementing Best Management Practices to protect groundwater quality in the area. These practices will likely serve to protect surface water quality in the long run as well.

Table 2. Seasonal Average OWQI Results for Owyhee 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

Acknowledgment: Software used for trend analysis was the WQHydro package developed by Eric Aroner of WQHydro Consulting.

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