WATER QUALITY CONDITIONS IN A NATIONAL CONTEXT

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Seven major water quality characteristics were evaluated for stream sites in each NAWQA Study Unit. Summary scores for each characteristic were computed for all sites that had adequate data. Scores for each site in the Willamette Basin were compared with scores for all sites sampled in the 20 NAWQA Study Units during 1992-95. Results are summarized by percentiles; higher percentile values generally indicate poorer quality compared with other NAWQA sites. Water quality conditions at each site also are compared to established criteria for protection of aquatic life. Applicable criteria are limited to nutrients and pesticides in water, semivolatile organic compounds in bed sediment, and organochlorine pesticides and PCBs in bed sediment. (Methods used to compute rankings and evaluate aquatic life criteria are described by Gilliom and others, in press.)

EXPLANATION

Ranking of stream quality relative to all NAWQA stream sites --Darker colored circles generally indicate poorer quality. Bold outline of circle indicates one or more aquatic life criteria were exceeded.

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Nutrient concentrations in water were similar to those found nationally. Concentrations in two streams were in the top 25 percent of data from the 20 NAWQA Study Units. One stream drained a small agricultural basin, and the other received sewage treatment plant effluent. No exceedances of the aquatic life criterion for unionized ammonia were found.

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Pesticide concentrations in water generally were representative of those found in other NAWQA Study Units. At one urban and two agricultural sites, exceedances of aquatic life criteria occurred for azinphos-methyl, carbofuran, chlorpyrifos, and/or diazinon.

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Concentrations of organochlorine pesticides and PCBs in bed sediment and biological tissue were typical of those in other NAWQA Study Units; however, concentrations were among the highest 25 percent at three mostly agricultural sites. Lindane in bed sediment exceeded the aquatic life standard at one of these sites.

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Trace element concentrations in bed sediment were lower than typically found nationally, with concentrations at 7 of 10 sites falling in the bottom 50 percent of data from the 20 NAWQA Study Units. The three streams with concentrations in the top 50 percent of NAWQA data were the only streams draining basins with large urban areas.

Concentrations of semivolatile organic compounds in bed sediment were low compared with other NAWQA Study Units; however, one agricultural site and one urban site ranked in the top 25 percent nationally. No exceedances of aquatic life criteria were found at any of the sites shown.

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Fish community conditions in five streams draining basins with agricultural and/or urban influences ranked among the poorest 25 percent of streams sampled in other NAWQA Study Units, as determined by percentages of external anomalies and of species that are pollution tolerant, omnivorous, and non-native. At one agricultural site, fish were 99 percent non-native and 61 percent exhibited anomalies.

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Stream habitat conditions for five streams draining basins with agricultural and/or urban influences were among the worst found when compared with other NAWQA Study Units. The most common factors contributing to these conditions were poor riparian quality, high susceptibility to bank erosion, and a high degree of channel modification.

CONCLUSIONS

Nutrient and pesticide concentrations in Willamette Basin streams were typical of concentrations in streams from other NAWQA Study Units, as were concentrations of organochlorine pesticides and PCBs in streambed sediment and biological tissue.

Concentrations of trace elements and semivolatile organic compounds in bed sediment generally were low relative to other NAWQA Study Units.

Stream habitat and fish community conditions in agricultural and urban streams were among the most degraded compared with other NAWQA Study Units. Degraded habitat and fish community conditions generally occurred at the same sites.

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Five major water quality characteristics were evaluated for ground water studies in each NAWQA Study Unit. Ground water resources were divided into two categories: (1) drinking water aquifers, and (2) shallow ground water underlying agricultural or urban areas. Summary scores were computed for each characteristic for all aquifers and shallow ground water areas that had adequate data. Scores for each aquifer and shallow ground water area in the Willamette Basin were compared with scores for all aquifers and shallow ground water areas sampled in the 20 NAWQA Study Units during 1992-95. Results are summarized by percentiles; higher percentile values generally indicate poorer quality compared with other NAWQA ground water studies. Water quality conditions for each drinking water aquifer also are compared to established drinking water standards and criteria for protection of human health. (Methods used to compute rankings and evaluate standards and criteria are described by Gilliom and others, in press.)

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Radon concentrations in ground water were low relative to national conditions, with all areas falling in the lowest 50 percent of data from the 20 NAWQA Study Units.

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Nitrate concentrations in ground water were similar to those found in other NAWQA Study Units . Nitrate concentrations generally were low in ground water from domestic wells in the alluvial aquifer, although almost 10 percent of samples exceeded the USEPA MCL for nitrate in drinking water.

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Dissolved solids concentrations in ground water were low compared with other NAWQA Study Units. This is consistent with the maritime climate and the paucity of easily dissolved minerals in the geologic source rock of the Willamette Basin. The USEPA Secondary MCL for dissolved solids in drinking water was exceeded in water from two domestic wells in the alluvial aquifer.

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Detections of volatile organic compounds in ground water were typical of those found nationwide, but detection rates in urban wells in the Portland area were within the top 25 percent of NAWQA data. The USEPA drinking water MCL for tetrachloroethylene was exceeded in water from one domestic well in the alluvial aquifer.

Pesticide detection rates in ground water typically were low compared with other NAWQA Study Units, especially for urban and nonirrigated agriculture areas. The MCL for dinoseb was exceeded in water from one domestic well in the alluvial aquifer.

CONCLUSIONS

Radon and dissolved solids concentrations, and pesticide detection rates in Willamette Basin ground water generally were low when compared with other NAWQA Study Units.

Nitrate concentrations and detection rates for volatile organic compounds were fairly typical of those found in other NAWQA Study Units.

Although a few exceedances of USEPA drinking water standards were noted in ground water from domestic wells in the alluvial aquifer, water quality generally was good.