8091 - Laserfiche WebLink

Home Browse Search

INTRODUCTION The Vernal Field Station formally initiated the White River Project in 1981, according to provisions of the U.S. Fish & Wildlife Service (FWS) - Bureau of Land Management (BLM) Memorandum of Understanding (No. CO-910-MU-9-933) signed April 1981. However, a preliminary survey in late 1980 was conducted with FWS funds. Sampling of approximately 150 mi (241 km) of the White River began on April 13, 1981. The field work was divided into a standardized sampling program and a special investi- gations program. The standardized program characterized fishery habitat and the general distribution and abundance of all fishes. The special investigations program provided in-depth studies of the life history of rare and endangered fishes. Setting The Colorado River basin is separated into upper and lower basins near Lee's Ferry, Arizona. The upper basin is further subdivided into its three major river systems or hydrologic subbasins; Green, Upper Main Stem and the San Juan-Colorado (Figure 1). The White River is a major tributary to the Green River subbasin. This river arises in western Colorado in the Flat Top Mountains and flows uninterrupted westerly for approximately 250 mi (?02 km) before joining the Green, draining over 5,019.3 mi (13,000 km ) of northwestern Colorado and eastern Utah. The White River study area (Figure 2) extended from Rio Blanco Lake (an offstream reservoir) Colorado at an elevation of 5650 ft (1723 m) above mean sea level (MSL) to its confluence with the Green River near Ouray, Utah an e1evation'of'4660 ft (1421 m) MSL, a distance of 150 mi (241 km). The upper portion of the study area is bordered by agricultural land comprised of alfalfa fields, permanent pastures and some grain and corn crops. A large quantity of land is used for livestock grazing. In addition, boulders, car bodies, miscellaneous debris and railroad ties have been placed in the river along banks and bends for attempted bank stabilization. The upper portion of the White River study area has a substrate of large-to-medium cobble produced as a result of high velocity flows and steep gradient (0.75 m/km). Sands and silts tend to accumulate in slower areas where the river reaches warm summer temperatures near 20°C. The lower portion of the river is characterized by warm and turbid water. Sand and silt substrates are formed from shale rock and are easily moved by seasonal floods from desert tributaries. Objectives The objectives of this study were: 1) to determine the biological significance of the White River for endangered Colorado River fishes, including their distribution, abundance and habitat requirements; and 2) to determine the characteristics and availability of endangered fish habitat in the White River under various flow regimes (runoff stages).