A water quality analysis of the Elwha River, WA, Watershed prior to anadromous fisheries restoration

McCormick, Robert D.
Paul M. Kotila
Department of Environmental Studies
1996
A six month, pilot water quality monitoring project was conducted in the Elwha River (WA) watershed to document baseline water chemistry, evaluate potential seasonal variations in water quality and examine potential influences of the Glines Canyon Dam on water quality. Water samples were collected from May to September, 1995 from six tributary and mainstream sites measured for levels of ortho-phosphorus, total phosphorus, total Kjeldahl nitrogen, nitrate-nitrogen and nitrate-nitrogen (nitrate/nitrate), calcium, potassium, sodium, magnesium, pH and water temperature. Samples showed overall water quality to be nutrient poor with low levels of total Kjeldahl nitrogen (0.030-0.050 ppm), nitrate-nitrate (0.001-0.030 ppm), total phosphorus (0.005-0.046 ppm) and ortho-phosphorus (0.001-0.040 ppm). Sodium (1.350-3.850 ppm), potassium (0.100-0.390 ppm) and magnesium (0.618-1.653 ppm) were also quite low while calcium levels were comparatively high (10.140-18.25 ppm). pH levels indicated slightly alkaline water conditions (6.7-7.1 units) and moderate water temperatures (6.0-14.0 ºC). Mainstream sites differed significantly (p<0.05) from tributary sites for levels of nitrate/nitrate, sodium, potassium, calcium, magnesium and discharge. Data grouped into high flow conditions (May, June and July) and low flow conditions (August and September) had significantly different levels of nitrate/nitrate, total phosphorus, sodium, calcium, magnesium, temperature and discharge. Samples collected above and below the Glines Canyon Dam had significantly different levels of nitrate/nitrate, total phosphorus and water temperature.

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