Water quality in the Willamette Basin, Oregon, 1991-95

Wentz, Dennis A.; Bonn, Bernadine; Carpenter, Kurt D.; Hinkle, Stephen R.; Janet, Mary; Rinella, Frank A.; Uhrich, Mark A.; Waite, Ian R.; Laenen, Antonius; Bencala, Kenneth E.

doi:10.3133/cir1161

Cited by 52 publications

(44 citation statements)

References 12 publications

(12 reference statements)

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“…Shallow groundwater in urban areas of the Willamette Basin near Portland, OR, has a median nitrate concentration of 5.4 mg/L. In 1990, about 1.2 million people lived in Portland, the state's largest metropolitan area (36). The median population density within 500 m of sampled wells in the Portland area is 2300 people/km 2 ( Figure 7).…”

Section: Figure 2 Distributions Of (A) Nitrite Plus Nitrate (B) Ammmentioning

confidence: 99%

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Nutrients in Groundwaters of the Conterminous United States, 1992−1995

Nolan

Stoner

2000

Environ. Sci. Technol.

212

180

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Results of a national water quality assessment indicate that nitrate is detected in 71% of groundwater samples, more than 13 times as often as ammonia, nitrite, organic nitrogen, and orthophosphate, based on a common detection threshold of 0.2 mg/L. Shallow groundwater (typically 5 m deep or less) beneath agricultural land has the highest median nitrate concentration (3.4 mg/L), followed by shallow groundwater beneath urban land (1.6 mg/L) and deeper groundwater in major aquifers (0.48 mg/L). Nitrate exceeds the maximum contaminant level, 10 mg/L as nitrogen, in more than 15% of groundwater samples from 4 of 33 major aquifers commonly used as a source of drinking water. Nitrate concentration in groundwater is variable and depends on interactions among several factors, including nitrogen loading, soil type, aquifer permeability, recharge rate, and climate. For a given nitrogen loading, factors that generally increase nitrate concentration in groundwater include well-drained soils, fractured bedrock, and irrigation. Factors that mitigate nitrate contamination of groundwater include poorly drained soils, greater depth to groundwater, artificial drainage systems, intervening layers of unfractured bedrock, a low rate of groundwater recharge, and anaerobic conditions in aquifers.

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Section: Figure 2 Distributions Of (A) Nitrite Plus Nitrate (B) Ammmentioning

confidence: 99%

“…The lower value represents nonirrigated agriculture and the higher value represents irrigated agriculture. Compared with nonirrigated crops, nitrogen application rates generally are greater on irrigated land (36), and irrigation increases groundwater recharge and subsequent leaching of nitrate.…”

Section: Figure 2 Distributions Of (A) Nitrite Plus Nitrate (B) Ammmentioning

confidence: 99%

Nutrients in Groundwaters of the Conterminous United States, 1992−1995

Nolan

Stoner

2000

Environ. Sci. Technol.

212

180

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“…Geological Survey's (VSGS) National Water-Quality Assessment (NAWQA) Program. The Willamette Basin study unit (Figure 1) comprises 31,000 km 2 in the Willamette and Sandy River Basins in northwestern Oregon (Wentz et al 1998). Thirteen major reservoirs regulate flows in the main stem during both wet and dry seasons.…”

Section: Introductionmentioning

confidence: 99%

Relations of Habitat-Specific Algal Assemblages to Land Use and Water Chemistry in the Willamette Basin, Oregon

Carpenter¹,

Waite²

2000

Monitoring Ecological Condition in the Western United States

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Abstract. Benthic algal assemblages, water chemistry, and habitat were characterized at 25 stream sites in the Willamette Basin, Oregon, during low flow in 1994. Seventy-three algal samples yielded 420 taxa -mostly diatoms, blue-green algae, and green algae. Algal assemblages from depositional samples were strongly dominated by diatoms (76% mean relative abundance), whereas erosional samples were dominated by blue-green algae (68% mean relative abundance).Canonical correspondence analysis (CCA) of semiquantitative and qualitative (presence/absence) data sets identified four environmental variables (maximum specific conductance, % open canopy, pH, and drainage area) that were significant in describing patterns of algal taxa among sites. Based on CCA, four groups of sites were identified: streams in forested basins that supported oligotrophic taxa, such as Diatoma mesodon; small streams in agricultural and urban basins that contained a variety of eutrophic and nitrogen-heterotrophic algal taxa; larger rivers draining areas of mixed land use that supported planktonic, eutrophic, and nitrogen-heterotrophic algal taxa; and streams with severely degraded or absent riparian vegetation (> 75% open canopy) that were dominated by other planktonic, eutrophic, and nitrogen-heterotrophic algal taxa. Patterns in water chemistry were consistent with the algal autecological interpretations and clearly demonstrated relationships between land use, water quality, and algal distribution patterns.

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“…Use on private forest lands is more common but still limited in extent. Water quality sampling programs in the Willamette River basin indicate that nitrogen and phosphorus concentrations in waters flowing from forested watersheds are similar to those at national benchmark sites on streams minimally disturbed by human activities (Wentz et al 1998). …”

Section: Nutrients and Contaminants-mentioning

confidence: 91%