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UPPER/MIDDLE SNAKE RIVER BASIN STATUS REPORT, 1975
Description:
The Snake River (17040104, 170402, 170501) begins with relatively high water quality, with nutrient levels below those considered potentially causative to algal activity. Below Heise, nutrient concentrations rise and the quality of the river is degraded. Phosphorus enters the Snake River through all of the major tributaries, but particularly via the Malheur, Weiser, and Portneuf Rivers. The Portneuf River receives phosphorus from 2 phosphate reduction plants at Pocatello, J.R. Simplot, and FMC. The Portneuf River enters the Snake in the American Falls Reservoir, which is characterized by high phosphorus levels, and depressed dissolved oxygen concentrations. American Falls Reservoir acts as a sink for phosphorus, heavy metals, and pesticides. Nitrogen concentrations in the Snake River increase significantly below Heise. This can be attributed largely to groundwater inflow in the Hagerman Valley reach. Generally, the Snake River in its upper portion has relatively low nutrient concentrations. However, during its flow it is influenced by its major tributaries (particularly the Portneuf River) and groundwater inflow, and becomes a river characterized by high nutrient levels. Kreizenbeck, R., R. Hauck, and D. Houck. 1975. Surveillance and Analysis Division, EPA Region X, Seattle, WA. 408 pp.