Laboratory and Environmental Assessment
Oregon Water Quality Index
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Oregon Water Quality Index Report for Rogue Basin
Water Years 1986-1995
The Rogue Basin and its five subbasins drain an area of diverse geology and land usage. In the past, water quality problems in the basin were identified. These problems were addressed in a small portion of the basin with the issuance of the Bear Creek Total Maximum Daily Load. However, throughout the remainder of the basin, general water quality conditions have not significantly improved and concerns of point and non-point source pollution remain. Comparing minimum seasonal Oregon Water Quality Index (OWQI) values (Table 1), water quality in the Rogue basin ranges from good (Rogue River at Dodge Park site) to very poor (Bear Creek at Talent). For most monitoring sites in the Rogue Basin, 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 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 Rogue Basin (WY 1986 -1995)
Summer: June - September; FWS ( Fall, Winter, & Spring): October - May
Upper Rogue Subbasin
The upper Rogue River receives drainage from the Cascades and has excellent general water quality. The upper reaches of Little Butte Creek provide some of the most productive salmonid spawning areas in the Rogue Basin. However, the lower reaches of the creek suffer from non-point source pollution, as indicated at the monitoring site located near the mouth of Little Butte Creek.
The Rogue River at Dodge Park is the most upstream monitoring site in the Rogue Basin and is situated upstream of all major point sources. Water quality at this point is the best of the monitored sites in the Rogue Basin. Relatively high concentrations of total phosphates and biochemical oxygen demand occasionally limit water quality at this site. These events occur during precipitation events (organic matter is deposited with runoff) and during periods of low flow (less water available to dilute organic matter). Water quality at the Rogue River at Dodge Park is good in the summer and excellent in the fall, winter, and spring (Table 1).
Contrarily, water quality at Little Butte Creek at Agate Road is consistently poor year-round (Table 1). High levels of fecal coliform, total phosphates, total solids, and biochemical oxygen demand impact general water quality in Little Butte Creek all year, except during periods of high flow and low or no precipitation. This indicates the introduction of untreated animal or human waste and runoff mainly associated with non-point sources. High stream temperatures in the summer compound water quality problems by increasing chemical and biological activity. It should be noted that irrigated agriculture and range dominate land uses on Little Butte Creek. Urban runoff from Eagle Point may contribute to non-point source pollution as well.
Middle Rogue Subbasin
The Middle Rogue Subbasin is the most impacted in the basin. These impacts are a result of the cumulative effects of point and non-point source pollution in the Bear Creek Valley, which is the most densely populated and intensively cultivated area in the Rogue Basin. The Bear Creek Total Maximum Daily Load (TMDL) coordinates efforts to reduce point and non-point source pollution. During water years 1986-1995, water quality data were routinely collected by the DEQ Laboratory at three monitoring sites on Bear Creek: Mountain Avenue (1986-1993), Valley View Road (1986-1993), and Kirtland Road (1986-1995). It is important to remember that comparison of results between these sites is applicable only to data collected in 1986-1993, and may not necessarily reflect more recent conditions.
The Mountain Avenue monitoring site is situated above the major point source of pollution on Bear Creek, the Ashland Sewage Treatment Plant (STP). Therefore it is mainly affected by non-point sources. Summer flows are maintained by releases from Emigrant Lake, which is supplemented by Howard Prairie Lake and Hyatt Reservoir. During the fall, flows are negligible while the Emigrant Lake reservoir is filled. This creates conditions in which little water is available to dilute pollutants introduced into the stream. Upper Bear Creek receives demands from irrigated agriculture and rangeland. Oregon Water Quality Index results show that this portion of Bear Creek was significantly impacted by high levels of total phosphates, fecal coliforms, total solids, and biochemical oxygen demand. On the average, OWQI results at the uppermost site on Bear Creek are poor throughout the year (Table 1). Water quality at the uppermost Bear Creek site is only slightly worse than at the Little Butte Creek site.
The Valley View Road monitoring site is downstream of the confluence of Bear Creek with Ashland Creek. Ashland STP presently discharges to Ashland Creek. OWQI results scored greater than 30 points only three times during the monitoring period and scored very poorly throughout the year (Table 1). The worst water quality conditions tend to occur in the fall, when flows are minimal. Extremely high concentrations of fecal coliforms, total phosphates, total solids, and biochemical oxygen demand are accompanied by low dissolved oxygen and extremely high levels of nitrate and ammonia nitrogen. High concentrations of ammonia were found. Ammonia nitrogen consumes oxygen during its conversion to nitrate nitrogen. This process is called nitrification and the demand on available dissolved oxygen is called nitrogenous oxygen demand.
By the time Bear Creek reaches the next monitoring site at Kirtland Road, reareation and mixing of the water has helped to improve water quality, but OWQI scores are still very poor throughout the year (Table 1). High concentrations of fecal coliform, total phosphates, total solids and biochemical oxygen demand still predominate water quality impacts. Low dissolved oxygen and high nitrate and ammonia nitrogens also impact water quality. High stream temperatures in the summer compound water quality problems by increasing chemical and biological activity. While effects from the Ashland STP may still be noticeable at this distance, it is likely that irrigation returns to Bear Creek contribute a significant amount of non-point source pollution to the creek. The Bear Creek at Kirtland Road monitoring site has been the only site maintained since establishment of the Bear Creek TMDL. Results of trend analysis indicate that no seasonally significant trend exists over the monitoring period of water years 1986-1995. It is important to note that population in the Bear Creek drainage had increased during that period. The lack of significant decreases in water quality may indicate that local efforts have been moderately successful. It is likely with further effort, significant improvements will be seen.
Results of monitoring the Rogue River at Rocky Point Bridge in Gold Hill indicate that general water quality has deteriorated compared to upstream conditions. Excellent quality is seen year-round at Dodge Park, while conditions at Rocky Point are generally good in the summer and only fair during the fall, winter, and spring (Table 1). This monitoring site is located a mile downstream of the Gold Hill STP. OWQI results are limited by high concentrations of fecal coliforms, biochemical oxygen demand, total phosphates, and total solids. These impacts are seen usually in connection with high flows, when higher loading from STP's, streams, and erosion are more likely to occur.
The Rogue River continues westward through Grants Pass before joining with the Applegate River at river mile 95 and turning north. The Applegate subbasin and Applegate River are monitored at US Highway 199. The Applegate River receives impacts from irrigated agriculture and other uses, such as mining. This monitoring site is impacted during high flow periods by high levels of fecal coliforms and biochemical oxygen demand. During the low flow summer months, high temperature and concentrated total solids and biochemical demand work to deplete dissolved oxygen concentrations. Applegate River OWQI values average good throughout the year (Table 1). Seasonal-Kendall trend analyses were performed on all of the Rogue Basin monitoring sites. The Applegate River site showed the only significant trend. It appears that non-point source pollution is contributing to a significant decrease in water quality in the Applegate River (Figure 1).
Figure 1. Trend Analysis Results for the Applegate River at US Highway 199
After the confluence with the Applegate River, the Rogue River arcs northward and then returns south to meet the Illinois River. In the Rogue Basin, water quality in the Illinois River and subbasin is rivaled only by water quality at the uppermost Rogue River site. The DEQ Laboratory routinely monitors the Illinois River downstream of Kerby, on the southwest side of Eight Dollar Mountain. While water quality is better in the Illinois River than the Rogue River during the fall, winter, and spring, high temperatures and lower flows impact the Illinois River in the summer. Low flow concentrates total solids and biochemical oxygen demand, while eutrophication becomes evident through high pH values and high dissolved oxygen supersaturation. In the Illinois River, OWQI values indicate that general water quality is, on the average, good in the summer and excellent in the fall, winter, and spring (Table 1).
Lower Rogue Subbasin
The Rogue River at the Robertson Bridge is approximately eight miles downstream of the confluence with the Applegate River and fourteen miles downstream of the Grants Pass STP. Thus, it is expected that impacts on water quality at this monitoring site will result mainly from local non-point sources. This section of the river is impacted by occasional high levels of fecal coliforms, biochemical oxygen demand, and total solids throughout the year. High temperatures are found during the summer. The effects of eutrophication are more clearly evident here (probably because it is not masked by gross contamination) in the form of high pH and high percentage of dissolved oxygen supersaturation. As a result, OWQI values remain fair throughout the year (Table 1).
During the reporting period of water years 1986-1995, DEQ Laboratory routinely monitored of the Rogue River at Lobster Creek Bridge beginning in 1992. Lobster Creek Bridge is sixteen miles downstream from the confluence of the Rogue River with the Illinois River. In the Rogue River at Lobster Creek Bridge, non-point sources contribute to high concentrations of total phosphates, total solids, and biochemical demand. As a result, eutrophication enhanced by the phosphates contributes to high pH values seen during summer low flow periods, when high temperatures also impact water quality. OWQI results indicate that water quality is good throughout the year at this most-downstream site (Table 1).
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.
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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