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150 UTAH ACADEMY PROCEEDINGS, VOL. 45, PART 1, 1968 Recording thermometers were maintained in the river at Little Hole, Echo Park, and Island Park in 1964-65, and at Little Hole and 0.8 km below Flaming Gorge Dam in 1967. Determinations of water temperature, turbidity, dissolved oxygen, pH, and alka- linity were made when bottom or drift samples were taken. Additional records on stream flow, water temperature, and water chemistry were obtained from the U. S. Geological Survey and the Utah Department of Fish and Game for the 1963-67 period. Bottom samples on hard substrates were taken with a wire- mesh device similar to that described by Waters and Knapp (1961). Ninety-five, 87, and 64 such samples were collected in 1964, 1965, and 1967, respectively. Samples on soft bottoms were taken with a 15.2-cm-square Ekman dredge. Sixteen and 36 samples were collected with the dredge in 1964 and 1965, respectively. Drift organisms were sampled with a conical nylon-mesh net (Nitex .#423) mounted on a 29.2-em-diameter hoop (Pearson and Frank- lin, 1968). Seventy-three and 321 drift-net samples were col- lected in 1964 and 1965, respectively. In 1967, drift organisms were collected at Little Hole with an automatic sampling device powered by a water-wheel anchored in the river. Results obtained with the automatic sampler were comparable to those obtained with the drift net since both devices filtered known volumes of water. RIVER ENVIRONMENT Stream. Flow Seasonal variations in flow have been greatly reduced since closure of the dam. In general, summer, fall, and winter flows have increased and spring flow has decreased. The lowest annual mean discharge observed at Greendale (0.8 KBD) was 6.7 m3/sec in 1963 and the highest was 76.1 m3/sec in 1967. Mean annual discharges were 44.3, 63.1, and 46.2 m3/sec in 1964, 1965, and 1966, respectively. Mean May-October postimpoundment flows were lowest in 1963 (2.8-3.7 M3 /see) and highest in 1967 (54.3- 91.4 m3/sec; Table 1). 1 Power demands on Flaming Gorge Dam often caused a diurnal fluctuation in flow. Maximum power production (and high flows) usually occurred during the daytime with a sharp drop in output in late afternoon. Reductions in flow from 70 to 10 m3/sec within an hour were common.