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` -6- of that species. The general location of these sites may be found on the accompanying map (Figure 1). With the upstream limits as starting points, a total mileage estimate of all the project waters downstream to the Flaming Gorge Damsite near Dutch John, .Utah was made by direct scaling from aerial photographs. 3 From past river-treatment programs, experience indicated that maximum treatment coverage and operational efficiency was obtained from rotenone introductions made at approximate ten-mile intervals. With the use of the aerial photographs, all major stream waters were arbitrarily divided into ten-mile sections, starting from the upstream limits. The U.S. Geological Survey maintains a system of water gauging stations on the Green River proper and many of its tributaries. From these stations the survey has compiled many years of daily flow data which are published annually in the Surface Water Supply papers for the Colorado Basin. ~ For this project records of flows for these stations were analyzed and volume of flow and velocity of the river was correlated with gauge height readings. A table was compiled indicating the average flow and velocity at all normal gauge heights. This made it possible for field personnel to have uncorrected river flow data immediately available. In order to carry out a treatment program with the greatest facility and economy, stream flows should be at the lowest level possible without involving other complicating factors. On the upper Green River drainage, the month of September was ascertained to be the time of lowest water flow concurrent with satisfactory water temperature and climatic conditions. Average September water flow estimates were calculated for all stations. Past river treatment experience indicated the necessity of making rotenone introductions at a 5 ppm concentration in order to maintain an adequate toxic level for carp throughout each ten-mile stream segment. Furthermore, it was considered that, for maximum lethal effectiveness, rotenone introduction should be continued for at least six hours from every station. Total rotenone requirements for average September flows were calculated with these criteria. To provide for the contingency that, at the actual time of treatment, water conditions might be above normal, rotenone requirements were also calculated for 1.36 and 1.6 times the average flow. Initial Testing of Rotenone Introduction Methods For its previous river treatment operations, the Wyoming Game and Fish Department had worked out a rotenone flow control system using automo- bile carburetors attached directly to the 55-gallon rotenone barrels (Peterson 1958). The system was very successful for stream flows under 100 cfs, but the Green River Project, with flows ranging from 200 cfs to a potential maximum of 1400 cfs, would require considerably greater rotenone releases than possible with the carburetor controls. In an effort to 3. U.S. Department of Agriculture - Contact Prints, 10"x10", Scale 1"=1667 ft. 4. U.S. Geological Survey Annual Surface Water Supply of the United States, Part 9, Colorado River Basin. Yearbooks for 1947 through 1961.