Author(s): B. W. Peterr; Andhassen A. Yassien; Ken I. Ashley; C. Wendell Koning; William G. Dunford; Lloyd Welder
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Abstract: For rivers which carry very low amounts of nutrients in the water, the productivity is limited by an impoverished food chain, that severely limits the growth of wild fish. Experiments in rivers in British Columbia, Canada, have shown that the addition of small amounts of phosphorus, and/or nitrate to these flows during the summer, has a most significant beneficial impact on productivity, and on fish. The cost of the liquid fertilizer is modest. In order to inject the liquid fertilizer efficiently, the final concentration must be approximately correct (about 5μg/l for phosphate), after dilution with the flow of the river. Hydrological work on several rivers that were selected showed that they were driven primarily by snow melt. During the summer period of interest, the rivers underwent a clearly defined snow-melt recession hydrograph. Research enabled the recession constant of the hydrographs to be found by analyzing river flow data from the region. For a fertilizer injection program that commenced at the start of the flow recession, the river discharge was measured on the start-up day (usually in early July), and the flow could be reliably predicted for the next two months. This observation enabled a low cost fertilizer injector to be conceived, built and tested. Details of the design and operation of the injector are briefly described.
Year: 1997