USGS Scientific Investigations Report 2012–5017  - Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009

Table 10. Nutrient concentrations for reference streams in the Cascade Range and Williamette Valley, Oregon, and nutrient and algal criteria to prevent nuisance conditions in streams. 

[Nutrient reference conditions suggested by the U.S. Environmental Protection Agency for streams in the Willamette Valley (Nutrient Ecoregion I, Subecoregion 3) and Cascade Range (Nutrient Ecoregion II, Subecoregion 4). Nutrient and algal criteria from Welch and others (1988). Abbreviations: < MRL, less than the method reporting level; mg/L, milligram per liter; mg/m², milligram per square meter] 

Nutrient	Number of sites	Minimum value	Maximum value	Reference condition (seasonal average) (mg/L)
Nutrient reference conditions (Willamette Valley)
Nitrite plus nitrate (NO₂+NO₃)	85	20	8,640	0.15
Total Kjeldahl nitrogen (TKN)	96	50	2,750	0.21
Total nitrogen (TN)	13	0	2,990	0.32
Total phosphorus (TP)	138	2	816	0.04
Nutrient reference conditions (Cascade Range)
Nitrite plus nitrate (NO₂+NO₃)	75	< MRL	1.910	0.005
Total Kjeldahl nitrogen (TKN)	65	< MRL	0.950	0.05
Total nitrogen (TN)	27	< MRL	2.860	0.055
Total phosphorus (TP)	95	< MRL	0.243	0.009
Nutrient and algal criteria to prevent nuisance conditions
Nutrient enrichment indicators	Criteria	Sites (dates) exceeding criteria		Maximum value
Dissolved inorganic nitrogen (NO₃+NH₄)	0.1 mg/L	Molalla River at Knights Bridge (Aug. 03 and Sept. 9, 2010)		0.327 mg/L
Soluble reactive phosphorus (SRP)	0.01–0.015 mg/L	Molalla River at Knights Bridge (Aug. 03 and Sept. 9, 2010)		0.013 mg/L
		Molalla River at Goods Bridge (Aug. 03 and Sept. 9, 2010)		0.011 mg/L
Total phosphorus (TP)	0.01–0.09 mg/L	Molalla River at Knights Bridge (Aug. 03 and Sept. 9, 2010)		0.015 mg/L
		Molalla River at Goods Bridge (Aug. 03 and Sept. 9, 2010)		0.011 mg/L
Benthic algae (periphyton) chlorophyll-a	100–150 mg/m²	Molalla River at Knights Bridge (Aug. 15, 2010)		113 mg/m²

Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009–10

Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009–10 