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Oregon Water Quality Index
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Oregon Water Quality Index Report for Lower Willamette, Sandy, and Lower Columbia Basins
Water Years 1986-1995
Lower Willamette Basin
For illustrative purposes, the Willamette Basin is separated into three parts: Upper Willamette, Middle Willamette, and Lower Willamette. The Upper Willamette includes the headwaters of the Coast and Middle Forks of the Willamette River, the McKenzie subbasin, and the mainstem Willamette River from the convergence of the forks to the point immediately upstream of the convergence with the Santiam River. The Middle Willamette extends to the Willamette River at Canby and includes the North and South Santiam, Yamhill, and Molalla-Pudding subbasins. The Lower Willamette extends to the mouth of the Willamette River and includes the Tualatin and Clackamas subbasins.
Water quality trends in the Lower Willamette Basin show significant improvement. Comparing minimum seasonal Oregon Water Quality Index (OWQI) values (Table 1), water quality in the Lower Willamette basin ranges from good (Clackamas River site) to very poor (Columbia Slough site). Water quality data were routinely collected by the DEQ Laboratory in 1986-1995. Special intensive studies were performed in the Tualatin and Lower Willamette subbasins in 1986-1990.
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 the Lower Willamette Basin (WY 1986 - 1995)
Summer: June - September; FWS ( Fall, Winter, & Spring): October - May
Water quality in the Tualatin Subbasin is influenced by logging operations, intensive agricultural and container nursery operations, confined animal feeding operations (CAFOs), industrial operations, municipal sewage treatment plants, urban nonpoint source pollution, and natural hydrological conditions. Because of the flat gradient of the primary streams in the subbasin, water flows slowly. Point and nonpoint source pollution is slowly moved to the Willamette and is not readily assimilated. Historically, water quality conditions in the Tualatin Subbasin have been very poor year-round. In 1988, the Tualatin River Total Maximum Daily Load (TMDL) was issued, instructing various agencies to comply with efforts to reduce point and non-point source pollution. Since 1988, general water quality conditions have significantly improved at all of the Tualatin Subbasin sites monitored by DEQ Laboratory. It's important to note that water quality has improved while population has significantly grown at the same time.
From its headwaters near Windy Point in the Coast Range to the floor of the Patton Valley east of Cherry Grove a dozen miles downstream, the Tualatin River descends 1800 feet. This reach of the river resembles a typical mountain stream with waterfalls, alternating pools and riffles, full canopies, fast flow, and cool temperatures. These conditions foster excellent water quality and salmonid habitat. However, as the river turns north at the Wapato Lake Bed and begins to meander across the Tualatin Valley floor for the subsequent seventy river miles, it descends only 250 feet in elevation. Most residents of the subbasin are only familiar with the water quality of the meandering lower Tualatin River.
Just north of the Wapato Lake Bed, the Tualatin River receives drainage from Scoggins Creek, a major tributary with the largest impoundment in the subbasin, Henry Hagg Lake. The Unified Sewerage Agency (USA) of Washington County purchases water for release from the lake during the summer to augment flows in the Tualatin River. This helps to reduce temperature and increases the assimilative capacity of the river. The Tualatin River receives drainage from Gales Creek before turning east. The Forest Grove Wastewater Treatment Plant (WWTP), a secondary treatment facility, discharges treated wastewater to the Tualatin River during high flow periods (typically November through April). After the river passes Forest Grove and Cornelius, it meets the combined drainages of Dairy and McKay Creeks at Jackson Bottom. USA manages Jackson Bottom as a wetland, providing habitat for wetland aquatic and avian species while utilizing the filtering effects wetlands provide. The Hillsboro (Westside) WWTP, a secondary treatment facility, discharges treated wastewater to the Tualatin River at Jackson Bottom during high flow periods.
Downstream of Jackson Bottom and upstream of the first major point source to the Tualatin River, the Rock Creek AWWTP (an advanced tertiary treatment facility), DEQ Laboratory monitors the river at Rood Road. Results from monitoring at this site reflect point source pollution from the Forest Grove and Hillsboro WWTP's (only during the high flow period) and nonpoint source pollution from silviculture, agriculture, container nurseries, confined animal feeding operations, erosion, and urban sources. Water quality at this site is the best of all DEQ-monitored sites in the Tualatin Subbasin. However, high concentrations of total phosphates, ammonia and nitrate nitrogens, fecal coliform and biochemical oxygen demand occasionally impact water quality at this site. These events usually occur in the late fall or early winter. On the average, OWQI scores for this site are poor throughout the year with better water quality conditions occurring in the summer (Table 1). Besides these water quality limiting events, general water quality has significantly improved over the last ten years (Figure 1). Institution of the Tualatin River TMDL and the subsequent improvements in management of point and non-point source pollution, including improvements at the Jackson Bottom Experimental Wetlands, are reflected by improvement of water quality in the upper stretches of the Tualatin River.
Figure 1. Trend Analysis Results for the Tualatin River at Rood Road
DEQ Laboratory monitors Beaverton Creek at 216th Avenue (now called Cornelius Pass Road) in Orenco, near the confluence with Rock Creek. Water quality in Beaverton Creek and its tributaries is influenced by nonpoint pollution as it passes through the urban, suburban, and industrial park areas of West Portland, Beaverton, and Aloha. Water quality has been frequently and severely limited by high concentrations of total phosphates, fecal coliforms, and total solids. High biochemical oxygen demand and high concentrations of ammonia and nitrate nitrogens also influence water quality at this site. Low dissolved oxygen concentrations were observed during summer months, indicating active eutrophication of Beaverton Creek. On the average, OWQI scores for this site are very poor throughout the year with better water quality conditions occurring in the fall, winter, and spring (Table 1). The frequency and intensity of the most severe impacts on water quality have lessened with improved management of nonpoint source pollution over time, and general water quality has significantly improved over the last ten years (Figure 2).
Figure 2. Trend Analysis Results for Beaverton Creek at 216th Street (Orenco)
After accepting discharge from Rock Creek and the Rock Creek AWWTP, the Tualatin River flows twelve miles through agricultural lands to the next monitoring site at Highway 210, north of Scholls. Due to sluggish river flow, little self-purification occurs. Very high concentrations of ammonia and nitrate nitrogen and total phosphates have been detected at this site. High concentrations of fecal coliform, total solids, and biochemicaloxygen demand also impact water quality. This indicates the presence of organicmatter and sediments in the water. Low dissolved oxygen concentrations wereseen in conjunction with high concentrations of ammonia nitrogen, meaning that ammonia was scavenging oxygen for conversion to nitrate nitrogen. This process is called nitrification. On the average, OWQI scores have been very poor throughout the year (Table 1). Starting in mid 1989, the Unified Sewerage Agency began to take steps to improve treatment of WWTP effluents as per the Total Maximum Daily Load instruction from the Oregon Department of Environmental Quality. The Rock Creek AWWTP began conversion of effluent ammonia nitrogen to nitrate nitrogen in August 1989. The new process had no net effect on ammonia and nitrate nitrogen scores in OWQI results because nitrate nitrogen concentration increased as ammonia nitrogen concentration decreased. However, the new process did reduce nitrogen-related biochemical oxygen demand, thus improving OWQI scores. The Rock Creek AWWTP began removal of phosphorous in August 1990. Due to the advanced treatment of nutrients in effluent, total solids concentrations increased. This is because an increased level of dissolved solids are a typical by-product of this advanced technology. The gain in water quality achieved by nutrient removal exceeds the impact of the increase in dissolved solids. A basin-wide phosphate detergent ban was instituted in February 1991. This ban had no direct impact on WWTP effluent as phosphates were already eliminated from the effluent, but it did decrease the cost of treatment of influent. The ban helped to decrease non-point source pollution from phosphate-based detergents entering streams via storm drains and faulty septic systems. As a result of these various factors, water quality significantly improved (Figure 3). The improvement seen at this site was the greatest improvement seen of all DEQ Laboratory-monitored sites in the state.
Figure 3. Trend Analysis Results for Tualatin River at HWY 210 (Scholls)
The Tualatin River continues to meander through Pleasant Valley, an area chiefly used for agricultural purposes, for eleven miles before reaching the next monitoring site at Elsner Road. Due to the sluggish flow, results at this site reflect local nonpoint source pollution and residual point source pollution not yet assimilated from Rock Creek AWWTP, prior to the facility's upgrades in 1989 and 1990. Water quality has improved compared to the Tualatin River at Highway 210. High concentrations of total phosphates, ammonia and nitrate nitrogen, total solids, and biochemical oxygen demand impact water quality in the Tualatin River at Elsner Road, but impacts are less severe than those at Highway 210. Low dissolved oxygen concentrations are seen in conjunction with high concentrations of ammonia nitrogen indicating active nitrification. At this site, nitrification is seen during low flow conditions. On the average, OWQI scores for the Tualatin River at Elsner Road are very poor throughout the year (Table 1). Like the previous site, water quality impacts on the Tualatin River at Elsner Road have lessened both in severity and frequency. Water quality has significantly improved at this site (Figure 4). This is due to improved management of point and nonpoint sources of pollution in the subbasin, primarily at the Rock Creek AWWTP.
Figure 4. Trend Analysis Results for Tualatin River at Elsner Road
DEQ Laboratory monitors Fanno Creek at Bonita Road, about two miles from the creek's confluence with the Tualatin River. The monitoring site is downstream of a light industrial park sited on previously grazed land. Water quality at this site was impacted by high concentrations of total phosphates, fecal coliform, total solids, and biochemical oxygen demand. Moderately high concentrations of ammonia and nitrate nitrogen accompanied high flows during fall, winter, and spring. High temperatures and low dissolved oxygen concentration in the summer months indicate eutrophication. OWQI scores are generally very poor throughout the year (Table 1). Historically, Fanno Creek was susceptible to pollution from urban and industrial sources, small sewage treatment plants, ineffective septic tanks and drainfields, CAFOs, agricultural operations, grazing, and illegal dumping. Concerns about public safety and environmental health prompted closure of the wastewater treatment plants in the seventies and reduced the number of permitted sources of pollution, while increased population pressures reduced the number of CAFOs and amount of agriculture and grazing in the Fanno Creek drainage. The ban on phosphate detergents, increased residential connection to municipal sewers, stormwater management, and increased public education have helped to reduce urban nonpoint sources of pollution to Fanno Creek. Water quality has significantly improved in Fanno Creek between 1986 and 1995 (Figure 5). Trout and their predators have returned to the upper reaches of Fanno Creek.
Figure 5. Trend Analysis Results for Fanno Creek at Bonita Road
From the monitoring site at Elsner Road, the Tualatin River flows nine miles through rural and suburban lands and receives discharge from Fanno Creek and the Durham AWWTP, an advanced tertiary treatment facility, before reaching the next monitoring site at Boones Ferry Road in Durham. This stretch of the Tualatin River flows faster than the other monitored stretches. This should allow for greater self-purification of the stretch, if it is not overburdened with pollutants. The Durham AWWTP dominates water quality impacts at this site, while Fanno Creek and sources upstream on the Tualatin River provide some influence on results. Very high concentrations of ammonia and nitrate nitrogen have been found at this site. High concentrations of total phosphates, fecal coliform, total solids, and biochemical oxygen demand also impact water quality. This indicates the presence of organic matter and sediments in the water. Low dissolved oxygen concentrations were seen in conjunction with high concentrations of ammonia nitrogen, meaning that ammonia was scavenging oxygen for conversion (nitrification) to nitrate nitrogen. High temperatures during the summer influences water quality by driving dissolved oxygen out of the water and increasing eutrophication and other chemical and biological activities. On the average, OWQI scores have been very poor throughout the year (Table 1). Starting in mid 1989, the Unified Sewerage Agency began to take steps to remove nutrients (ammonia nitrogens and total phosphates) from WWTP effluents as per the Total Maximum Daily Load. As previously mentioned, a basin-wide ban on phosphate detergents was instituted in February 1991. Ammonia nitrogen and phosphorous nutrients were consistently removed by the Durham AWWTP by 1994. The Durham AWWTP received upgrades similar to those upgrades at the Rock Creek AWWTP. Please see the discussion of water quality in the Tualatin River at Highway 210 for details on how these upgrades influenced changes in water quality in the river. Water quality has significantly improved at this site (Figure 6). The improvement in water quality at this site was the second greatest improvement seen among all DEQ Laboratory-monitored sites in the state.
Figure 6. Trend Analysis Results for Tualatin River at Boones Ferry Road
Changes in water quality management in the Tualatin basin have been positive. The major point sources in the subbasin have been improved to the point where they assist in diluting the effects of other sources during periods of low flow. It is likely that further improvements in nonpoint source related issues will continue to improve the quality of water in the Tualatin basin.
In sharp contrast to the Tualatin Subbasin, water quality in the Clackamas River is generally good throughout the year (Table 1). Most of the subbasin drains the Western and High Cascades and is used for silvicultural and recreational uses. The Clackamas River has three impoundments at and above the city of Estacada. The Estacada WWTP represents the sole municipal point source on the river, discharging above River Mill Dam. The Clackamas River is protected as a scenic waterway from River Mill Dam (river mile (RM) 23.2) to Carver Bridge (RM 8.0). The lower stretch of the river is increasingly pressured by population growth in Gladstone and Oregon City. DEQ Laboratory monitors the Clackamas River at High Rocks in Gladstone. Water quality is occasionally impacted by moderately high levels of biochemical oxygen demand. This indicates the introduction of organic materials to the water. Moderately high concentrations of fecal coliform and total phosphates have been seen during high flow periods. High levels of fecal coliform can be associated with the presence of untreated human or animal waste, indicating runoff from fields, ditches, and storm drains carrying organic material to streams and rivers in the subbasin. High temperatures and dissolved oxygen supersaturation during summer low flow periods indicates occasionally increased levels of eutrophication. Fortunately, the frequency of these occasional and moderate impacts has decreased over time, and water quality in the Clackamas River has significantly improved (Figure 7).
Figure 7. Trend Analysis Results for Clackamas River at High Rocks
Lower Willamette Subbasin
Lower Willamette Subbasin water quality is primarily influenced by municipal and industrial point sources and urban non-point sources, although rural nonpoint sources contribute to water quality conditions via Middle Willamette, Tualatin, and Clackamas Subbasins as well. Water quality deteriorates as the Willamette River flows downstream (Table 1).
The most downstream site in the Middle Willamette Subbasin is at the Canby Ferry (see Middle Willamette Subbasin report). The Willamette River receives several inputs before reaching the most upstream site in the Lower Willamette Subbasin at the Hawthorne Bridge in Portland. After leaving the Canby monitoring site, the Willamette River receives discharge from the Canby WWTP and flows past the last stretch of rural land before entering the Portland metropolitan area. The Willamette River converges with the Tualatin River and receives drainage from Abernethey Creek before it flows over Willamette Falls. The river receives discharge from the Tri-Cities WWTP, Clackamas River, Lake Oswego, Tryon Creek WWTP, Tryon Creek, Oak Lodge WWTP, Kellogg Creek, Kellogg WWTP, and Johnson Creek. As the Willamette River enters the Portland city limits, it is subjected to sand and gravel operations at Ross Island and wet weather combined sewer overflows.
Like Fanno Creek, Johnson Creek is largely an urban stream. Unlike Fanno Creek, Johnson Creek has not been assisted by a far-reaching TMDL. Since DEQ Laboratory began monitoring Johnson Creek at SE 17th Avenue in Portland in 1990, resulting OWQI scores were greater than 30 only twelve percent of the time. All results were in the "very poor" range of OWQI scores. Johnson Creek is impacted by very high concentrations of nitrate nitrogen and high concentrations of total phosphates, fecal coliform, total solids and biochemical oxygen demand also impair water quality at this site. These conditions occur throughout the year. This indicates the introduction of inorganic and organic materials and untreated human or animal waste, most likely a result of nonpoint source pollution. On the average, OWQI scores for Johnson Creek are very poor throughout the year (Table 1). Of all of the DEQ-monitored sites in the Willamette Basin, only the Columbia Slough scores are worse than Johnson Creek scores, in terms of minimum seasonal averages.
The Willamette River at Hawthorne Bridge in Portland is impacted by high concentrations of fecal coliform, total phosphates, nitrate and ammonia nitrogen, and biochemical oxygen demand with additional influence from high total solids. Given the large volume of water and variety of pollution sources, it is generally difficult to determine the exact cause of impacts to water quality at this site. However, the most severe impacts occur during winter, when Portland's combined sewer/stormwater system is under the most pressure and overflows are most likely to occur. On the average, OWQI scores for the Willamette River at Hawthorne Bridge are poor throughout the year (Table 1). The frequency of these events has decreased during the last five years, and water quality has significantly improved (Figure 8). It is likely that improvement of Clackamas River water quality and the great improvement of Tualatin River water quality influenced improvement in general water quality in the Willamette River.
Figure 8. Trend Analysis Results for Willamette River at Hawthorne Bridge (Portland)
Downstream of the downtown Portland area, the Willamette River is heavily used for transportation of goods. Various industrial storage facilities and shipyards line the contained riverbanks. A maintenance yard complete with dry dock facilities exists on Swan Island, which is really a peninsula made of dredge tailings. Since 1990, DEQ Laboratory has regularly monitored water quality in the Swan Island Channel, which is a deep backwater of the Willamette River used for docking ships. A combined stormdrain/sewer overflow (CSO) outfall is located at the head of the channel. Water quality is regularly impacted by high concentrations of biochemical oxygen demand, indicating the introduction of organic matter to the water. High concentrations of fecal coliform and total phosphates also impact water quality with additional influence from high total solids and nitrate and ammonia nitrogen. Summer water temperatures are relatively high and dissolved oxygen concentrations low, indicating eutrophication. On the average, WQI scores for the Swan Island Channel are poor throughout the year, with better conditions in the fall, winter, and spring (Table 1).
The Willamette River at the SP&S Railroad Bridge is six miles downstream of the Hawthorne Bridge. This site is impacted by the same sources impacting water quality at the Hawthorne Bridge, with the addition of industrial point and nonpoint source pollution. The Willamette River at the SP&S Railroad Bridge is impacted by high concentrations of fecal coliform, total phosphates, and biochemical oxygen demand with additional influence from moderately high concentrations of nitrate and ammonia nitrogen and total solids. Summer water temperatures can be relatively high and dissolved oxygen concentrations low, indicating eutrophication. On the average, OWQI scores for this site are poor throughout the year (Table 1).
Of all of the waterbodies in the Willamette Basin that are monitored by DEQ Laboratory, the Columbia Slough is the most severely impacted. Historically Portland's receiver of waste, the Columbia Slough has at times been impacted by the St. John's landfill, Columbia Boulevard WWTP, the meatpacking industry, and other heavy industries legally and illegally discharging waste. Presently, the landfill is closed, the WWTP outfall was moved to the Columbia River, the meatpacking industry closed, and other industries are less likely to dump to the slough. Current sources of pollution include combined sewer overflow, storm water drainage, airport runway maintenance, and golf course maintenance. High concentrations of total phosphates, ammonia and nitrate nitrogen, fecal coliform, biochemical oxygen demand, and total solids impact water quality in the Columbia Slough at Landfill Road, indicating that organic and inorganic matter, including untreated human or animal waste, are present in great abundance. During summer, high temperatures enhance hypereutrophic conditions, as evidenced by extremely high dissolved oxygen supersaturation and high pH. OWQI scores for the Columbia Slough are very poor throughout the year (Table 1). Of all of the DEQ-monitored sites in Oregon, the Columbia Slough at Landfill Road rates third worst water quality in terms of minimum seasonal averages.
The Sandy Basin drains the western slopes of Mt. Hood and a portion of the Western Cascades and includes the Bull Run Reserve, a protected watershed providing high quality drinking water to the City of Portland. The Sandy River is protected as a scenic waterway from Dodge Park (RM 18.8) to Dabney Park (RM 6.0). Unprotected lands are used primarily for silviculture and agriculture. DEQ Laboratory monitors the Sandy River at Troutdale Bridge. Water quality is occasionally impacted by moderately high levels of total phosphates and biochemical oxygen demand during high flows. This indicates the introduction of inorganic and organic materials to the water by runoff from fields, ditches, and storm drains. Moderately high temperatures during summer low flow periods have been noted. On the average, OWQI scores for the Sandy River are excellent throughout the year (Table 2).
Lower Columbia Basin
Even more so than the Willamette River, the enormous volume of water and wide variety of pollution sources to the Columbia River defy establishing cause and effect relationships between pollution and general water quality. Since 1990, DEQ Laboratory has regularly monitored the Columbia River at Marker 47, upstream of the confluence of the Willamette River. At the site, the Columbia River is impacted by high levels of biochemical oxygen demand and total solids, indicating the presence of organic matter and dissolved and suspended solids in the water. On the average, OWQI scores are poor in the summer and fair during the fall, winter, and spring (Table 2).
Table 2. Seasonal Average OWQI Results for the Sandy and Lower Columbia Basins (WY 1986 - 1995)
Summer: June - September; FWS ( Fall, Winter, & Spring): October - May;
Acknowledgment: Software used for trend analysis was the WQHydro package developed by Eric Aroner of WQHydro Consulting.
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. n.
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
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