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Scientific Investigations Report 2009–5078

Assessment of Eutrophication in the Lower Yakima River Basin, Washington, 2004–07

Table 12. Comparison of nutrient and algal biomass results to suggested U.S. Environmental Protection Agency reference conditions and algal biomass nuisance levels for the lower Yakima and Naches Rivers, July 1–September 30, 2004–07.

[Suggested reference conditions are from U.S. Environmental Protection Agency (2000b). Shading indicates values greater than the suggested U.S. Environmental Protection Agency reference conditions. Phytoplankton nuisance level established by the State of Oregon (Oregon Administrative Code, 2006). Periphyton nuisance level established by the Province of British Columbia (British Columbia Ministry of Environment, 2001). Zillah-WADOE, results from sampling done by the Washington State Department of Ecology at Nob Hill (RM 111). Abbreviations: RM, river mile; num, number of samples collected; per, percentage of values greater than reference condition or nuisance level; med, median value for all samples; mg/L, milligram per liter; μg/L, microgram per liter; mg/m2, milligram per square meter; –, no data]

Reach Suggested USEPA reference condition   Nuisance level
Nitrate plus nitrite 
as nitrogen
(0.072 mg/L)
  Total Kjeldahl nitrogen
(0.288 mg/L)
  Total nitrogen
(0.221 mg/L)
  Total phosphorus
(0.030 mg/L)
Phytoplankton chlorophyll a
(15 µg/L)
Periphyton
chlorophyll a
(100 mg/m2)
num per mean num per mean num per mean num per mean num per med num per med
Naches River 12 25 0.031   12 8 0.135   12 17 0.166   12 50 0.032   2 0 1.5 6 0 44
Zillah-WADOE (RM 111) 12 58 0.095 12 33 0.201 12 50 0.030
Zillah (RM 116–72) 87 79 0.317 79 9 0.197 86 79 0.478 80 100 0.059 21 14 4.6 36 37 80
Mabton (RM 72–47) 11 100 1.095 11 82 0.373 11 100 1.468 11 100 0.144 20 20 13 0
Kiona (RM 47–4) 22 100 0.875 20 25 0.256 22 100 1.108 20 100 0.140 16 6 4.4 1 0 8

For additional information contact:
Director, Oregon Water Science Center
U.S. Geological Survey
2130 SW 5th Avenue
Portland, Oregon 97201
http://or.water.usgs.gov

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