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n~?337 largest use of water from the Gunnison River downstream from Delta is for the Redlands Canal (fig. 3), which diverts water from the river 2 mi upstream from Grand Junction. Most of the water diverted for the Redlands Canal is for operation of a small powerplant. The Uncompahgre River downstream from Colona is used for agricultural irrigation, but not for domestic or municipal water supplies. The river is classified for agricultural uses and recreation by the State of Colorado (Colorado Department of Health, 1988). Downstream from Montrose, the river presently (1989) is not classified as a viable fishery by the Colorado Department of Health because of problems from previous metal pollution from headwater areas, warm stream temperatures in summer, and fluctuating stream discharge and sediment associated with irrigation practices. Less than normal snowmelt runoff and reservoir operations affected stream discharge in the Gunnison and Uncompahgre Rivers in water year 1988. Stream discharge of the Gunnison River has been partially regulated since 1937 by Taylor Park Reservoir and much more regulated since 1965 by Blue Mesa Reservoir. Stream discharge in the Uncompahgre River during water year 1988 was affected by the filling of Ridgway Reservoir that began in the fall of 1986. The annual stream discharge of the Gunnison River at Delta (gaging sta- tion 09144250 in figs 1 and 3) in water year 1988 was about 55 percent of the average annual stream discharge for water years 1977-87. This gaging station has only operated since May 1976. To compare stream discharge in 1988 to the average stream discharge for water years 1966-87, the stream-discharge record for Gunnison River near Grand Junction (gaging station 09152500, figs. 1 and 3) was used. Water years 1966-87 were used as the long-term period because those years represent stream discharge in the river since completion of Blue Mesa Reservoir. The annual stream discharge for gaging station 09152500 in water year 1988 was about 71 percent of the average annual stream discharge for water years 1966-87. The daily mean stream discharges from October to about mid April in water year 1988 were about equal to the average daily mean stream discharges for water years 1966-87 (fig. 4). Releases from Blue Mesa Reservoir were not increased substantially in spring and summer of 1988 because of less than normal snowmelt runoff into the reservoir. The monthly mean stream discharges in May, June, and July of 1988 were only about 35 to 40 percent of the long-term average monthly mean stream discharges for those months for water years 1966-87. Natural runoff in the Uncompahgre River basin upstream from Ridgway Reservoir is represented by the stream-discharge record for Uncompahgre River at Ridgway (gaging station 09146200 in fig. 1). The annual stream discharge at Ridgway for water year 1988 was about 80 percent of the average annual discharge for the period of record (water years 1959-87). Stream discharge for Uncompahgre River at Colona (gaging station 09147500 in fig. 1) during water year 1988 was primarily dependent on releases from Ridgway Reservoir. The annual stream discharge at Colona for water year 1988 was only about 53 percent of the average annual stream discharge for the period of record (water years 1913-87). Stream discharge was greatly decreased during spring runoff in 1988 compared to the long-term average (fig. 5). Monthly mean stream discharge in May 1988 was only about 27 percent of the average monthly mean discharge for May, and stream discharge in June was only about 34 percent of the average monthly mean discharge for June. 13