Oregon Water Quality Index Report for Deschutes and Hood Basins

Water Years 1986-1995

Deschutes Basin

The Deschutes Basin is comprised of two distinct sets of subbasins. The Deschutes River subbasins mainly drain the High Cascades while the Crooked River subbasins drain the Ochoco Mountains. This is significant as the geology and water chemistry of the Crooked River subbasins resembles the John Day Basin more closely than the Deschutes River subbasins. Water quality in the Deschutes Basin is influenced by logging operations, recreational uses, residential growth, grazing, confined animal feeding operations (CAFOs), and associated irrigated and nonirrigated agricultural operations. Water quality trends in the Deschutes Basin show significantly decreasing water quality over time at the Deschutes River at Warm Springs. Comparing minimum seasonal Oregon Water Quality Index (OWQI) values (Table 1), water quality in the Deschutes Basin ranges from excellent (Metolius River site) to poor (Crooked River at Lone Pine Road site). Water quality data were routinely collected by the DEQ Laboratory in water years 1986-1995.

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 andaquatic 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 Deschutes 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
 

Upper Deschutes Subbasin

The Upper Deschutes Subbasin drains a variety of landscapes, including the High Cascades, lava plateaus, and high desert basins and ranges. Precipitation decreases from west to east. The subbasin includes the Deschutes River from its headwaters to Lake Billy Chinook, the Metolius River, Squaw Creek, and numerous smaller tributaries. The Little Deschutes River joins the Deschutes River upstream of Sunriver. Water in the Upper Deschutes basin is highly regulated, with impoundments at Crane Prairie Reservoir, Wickiup Reservoir, and Lake Billy Chinook. Much of the flow of the Deschutes River above Bend is diverted to irrigation canals. Water quality in the Deschutes River generally declines from upstream to downstream.

In late 1995, the DEQ Laboratory ambient water quality monitoring network was expanded to include the Little Deschutes River and the mainstem Deschutes River at Pringle Falls, but for purposes of this report, the most upstream site monitored was the Deschutes River at Harper Bridge in Sunriver. The Harper Bridge site is approximately one mile downstream of the confluence of the Deschutes River with the Little Deschutes River. Occasional spikes in total phosphate levels and high levels of biochemical oxygen demand were detected at this site. There are no significant point sources upstream of this monitoring site. The Little Deschutes River is pressured by increasing population in the La Pine area and attendant increases in the number of septic systems. Irrigation withdrawals from and returns to the Little Deschutes River influence water quality conditions. High levels of total phosphates in the Crane Prairie and Wickiup Reservoirs influence downstream conditions when impounded waters are released. Impacts from recreational uses, golf course maintenance for instance, also influence results. Fortunately, these conditions impact water quality at this monitoring site infrequently and only moderately in magnitude. General water quality conditions in the Deschutes River at Harper Bridge are good in the summer and excellent during fall, winter, and spring (Table 1).

Downstream of the Sunriver recreational area, the Deschutes River passes through meadows, lavafields, and agricultural diversion dams before entering Bend. The next site downstream monitored by the DEQ Laboratory is the Deschutes River at Mirror Pond, an impoundment in central Bend. Drake Park surrounds Mirror Pond, and waterfowl enjoy the safety of the pond. They may be a contributing factor to elevated total phosphates, biochemical oxygen demand, and pH. Urban runoff may also contribute to these conditions. Elevated pH, seen during the summer months when water temperatures are warmer, indicate active eutrophication in the pond. Water quality is slightly impaired with respect to conditions at Harper Bridge, but is still good year-round (Table 1).

As the Deschutes River leaves Bend, some of its flow is diverted for agricultural uses. The river then enters the warmer and drier desert environment. The next site downstream on the Deschutes River is at Lower Bridge, about five miles west of Terrebonne. The Oremite mine adjacent to the monitoring site historically extracted diatomaceous earth. Due to the relatively warm temperatures and abundance of phosphorous, eutrophication is active from April until October, as evidenced by high pH and dissolved oxygen values. Interestingly, water at this site was supersaturated with respect to oxygen in all but one of the samples taken during this ten year period. High water temperatures are experienced during the low-flow summer months, and high levels of biochemical oxygen demand and total phosphates are detected throughout the year. Water quality in the Deschutes River at Lower Bridge more closely resembles conditions in the Upper Crooked Subbasin than conditions in the rest of the Upper Deschutes Subbasin. On the average, water quality at this monitoring site is fair in the summer and good in the fall, winter, and spring (Table 1).

DEQ Laboratory monitors the Metolius River at Bridge 99, approximately eleven miles downstream from its source and ten miles north of Camp Sherman. The Metolius River, considered as one of the outstanding resource waters of the state, converges with the Deschutes and Crooked Rivers at Lake Billy Chinook. Total phosphate concentrations in the Metolius River have background levels similar to background levels in the Deschutes River at Harper Bridge. This indicates the similar geology of the sources of both of these rivers, which is the eastern foothills of the High Cascades. During summer low-flow conditions, this background total phosphate concentration, combined with warmer temperatures, led to eutrophication of the Metolius River. This is evident as high levels of dissolved oxygen supersaturation and biochemical oxygen demand were occasionally detected. On the whole, OWQI scores at this monitoring site are excellent throughout the year (Table 1).

Upper Crooked Subbasin

As previously mentioned, since the Crooked River subbasins drain the Ochoco Mountains, the geology and water chemistry of the Crooked River subbasins resembles the John Day Basin more closely than the Deschutes River subbasins. Different soil types mean different natural background levels of total solids, pH, alkalinity, and other water chemistry parameters. The Upper Crooked Subbasin includes the tributaries to Beaver Creek, North and South Forks of the Crooked River, and the mainstem Crooked River down to and including the Prineville Reservoir. Land uses in the subbasin are, predominately, logging and grazing. DEQ Laboratory monitors water quality conditions in the Upper Crooked Subbasin on the Crooked River at Conant Basin Road. This monitoring site is situated in a grazed pasture. Eutrophication is active during the low-flow summer months when water temperatures are high, as indicated by high levels of pH and dissolved oxygen supersaturation. High concentrations of biochemical oxygen demand during the summer indicate the presence of algae or other organic material. High concentrations of total solids throughout the year indicate continual erosion of soils in the subbasin. High concentrations of total phosphates are present during the summer as less water is available for dilution. This high concentration fuels the eutrophication process. During heavy precipitation, very high concentrations of total phosphates were detected, indicating erosion or flooding of upstream pastures. Water quality in the Crooked River at Conant Basin Road is generally poor throughout the year (Table 1).

Lower Crooked Subbasin

Lower Crooked Subbasin water quality is influenced by logging, grazing, irrigated and nonirrigated agriculture, confined animal feeding operations (CAFOs), recreation, urban non-point source pollution, and seasonal sewage treatment plant (STP) operations. The Lower Crooked Subbasin includes the tributaries to Ochoco Creek and the mainstem Crooked River from Bowman Dam to the confluence with the Deschutes River at Lake Billy Chinook. Flow in the lower Crooked River is regulated by releases from the Prineville and Ochoco Reservoirs. Water quality in the Crooked River deteriorates as it moves downstream.

DEQ Laboratory monitored the Crooked River at HWY 126 in Prineville from 1988 to 1993. Water quality at this monitoring site is similar to water quality at the Conant Basin Road site. An exception is eutrophication was more clearly evident earlier in the year at Prineville. High pH and dissolved oxygen supersaturation were detected as early as April. High water temperatures were detected during the summer months. High concentrations of biochemical oxygen demand, total phosphates, and total solids were detected throughout the year. Spikes in total phosphate levels, related to heavy precipitation, were seen simultaneously with total phosphate spikes at Conant Basin Road. Generally, OWQI values for the Crooked River at HWY 126 in Prineville were poor throughout the year (Table 1).

Downstream of the monitoring site in Prineville, the Prineville STP is permitted to release treated wastewater to the Crooked River during high flow conditions. Ochoco Creek converges with the Crooked River approximately one mile below the Prineville STP. The Crooked River meanders through the Prineville Valley before passing the monitoring site at Lone Pine Road, near the head of the Crooked River Gorge. The effects of land usage on water quality is pronounced at this site. Irrigated agriculture supports CAFOs and grazing in the vicinity of this monitoring site. Like the upstream Crooked River sites, eutrophication was evidenced by high pH and dissolved oxygen supersaturation. High water temperatures were detected during the summer months. High concentrations of biochemical oxygen demand, total phosphates, and total solids were detected throughout the year. Spikes in total phosphate levels, related to heavy precipitation, were seen simultaneously with total phosphate spikes at Conant Basin Road. However, unlike the upstream sites, results of monitoring at the Crooked River at Lone Pine Road indicate elevated levels of fecal coliforms and nitrate and ammonia nitrogen at various times throughout the year. These additional impacts led to a general depression in water quality relative to upstream conditions. Seasonal average OWQI scores for the Crooked River at Lone Pine Road are about ten points below scores for the most upstream site (Table 1).

Lower Deschutes Subbasin

Like the Lower Crooked Subbasin, Lower Deschutes Subbasin water quality is influenced by logging, grazing, irrigated and nonirrigated agriculture, confined animal feeding operations (CAFOs), recreation, urban non-point source pollution, and sewage treatment plant (STP) operations. The Lower Deschutes Subbasin includes the tributaries to Shitike Creek, Trout Creek, Warm Springs River, White River, and the Deschutes River from the Round Butte Dam and Lake Simtustus to the mouth at the Columbia River. The Deschutes River is designated as a national scenic waterway from the foot of Lake Simtustus at Pelton Dam to the mouth, with the exception of the stretch of the river in the town of Maupin. This stretch of the river is heavily used for rafting and fishing. Flow in the lower Deschutes River is regulated by releases from Lakes Billy Chinook and Simtustus. Water quality in the Deschutes River slightly deteriorates as it moves downstream.

DEQ Laboratory monitors the Deschutes River at HWY 26 in Warm Springs, three miles downstream of the Regulator Dam. Flow at this monitoring site is significantly greater than at the Deschutes River at Lower Bridge site, due to the confluence of the Crooked and Metolius Rivers with the Deschutes River at Lake Billy Chinook. This increased flow is accompanied by improved water quality, compared to the Lower Bridge site. High levels of biochemical oxygen demand and total phosphates occur during late summer, when flows are lowest and less dilution takes place. Heavy precipitation causes erosion, which also increases biochemical oxygen demand and total phosphates, as well as total solids. On the average, OWQI scores for the Deschutes River in Warm Springs are good throughout the year (Table 1), however, water quality at this site has significantly decreased between water years 1986 and 1995 (Figure 1). This decrease occurred during the months of May through October. Results from monitoring of this site are indicative of local conditions and, perhaps even more influential, of the cumulative effects of water quality conditions in the Upper Deschutes and Crooked Subbasins.

Figure 1. Trend Analysis Results for the Deschutes River at Warm Springs

While the Deschutes River downstream of Warm Springs is itself used primarily for recreational purposes, other streams discharging to the Deschutes River drain lands used for logging and ranching. The city of Maupin STP is permitted to discharge treated wastewater to the Deschutes River. The most downstream site in the basin is on the Deschutes River at Deschutes River State Park, near the mouth of the river. This stretch of the river is used predominantly for sport fishing. High levels of biochemical oxygen demand, total phosphates, and total solids impact water quality at this site throughout the year. The worst impacts occur during periods of heavy precipitation. High temperatures, pH, and dissolved oxygen supersaturation have been detected during summer low-flow periods, indicating eutrophication. On the average, OWQI scores for this site are fair throughout the year (Table 1).

Hood Basin

The Hood Basin drains the northern and eastern slopes of Mt. Hood. Lands are used primarily for logging and irrigated and non-irrigated agriculture. The DEQ Laboratory monitored Hood River in the city of Hood River initially at the HWY 30 Bridge and presently at the footbridge north of Interstate 84. Water quality is occasionally impacted by high levels of total phosphates, biochemical oxygen demand, and fecal coliform during heavy precipitation and high flows. This indicates the introduction of inorganic and organic materials to the water by erosion and runoff from fields, ditches, and storm drains. Moderately high temperatures, and high levels of total phosphates, biochemical oxygen demand, and total solids during summer low flow periods have been noted. These concentrations increase as less water is available for dilution. On the average, OWQI scores for Hood River are good in the summer and fair during the fall, winter, and spring (Table 2).

Table 2. Seasonal Average OWQI Results for Hood 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