Author(s): C. Holderman; G. Hoyle; Ryan Hardy; Paul Anders; Peter Ward; Hassen Yassien
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Abstract: Construction of Libby Dam, a large hydropower and flood control dam was completed on the Kootenai River, near Libby, Montana in the Northwestern United States in 1972. Downstream river discharge, thermal regimes, nutrient availability, and dependent habitat conditions and ecological functions have been significantly altered by dam construction and operation. In response to ultraoligotrophic conditions downstream from Libby Dam, experimental additions of phosphate fertilizer solution (ammonium polyphosphate, 10-34-0) at in-river target concentrations of 1.5 and 3 μ g/L along with N/P ratios > 15:1were implemented. A solar-powered nutrient addition system was custom built to dose small releases of dissolved nutrients at rates from 10 to 40 L/hour, depending on river discharge, averaging several hundred m3/s. Positive responses in nutrient availability, primary, and secondary productivity, including biomass, abundance, and species richness were observed following nutrient addition. Data collection and analysis will be ongoing through 2009.
Year: 2009