8259 - Laserfiche WebLink

Home Browse Search

Vegetation and Land Use The Big Sandy River basin has ten major vegetation types: Sage- brush-grass, saltbrush, meadow, grass, greasewood, perennial forbes, mountain shrub, conifer, barren, and waste (U.S. Bureau of Land Manage- ment, 1978, p. 2-3). The distributions of these vegetation types are shown in figure 9. Sagebrush-grass is the dominant vegetation type in the Big Sandy River basin. Land is used chiefly for grazing but can be productive farmland where irrigated. Farming in the Big Sandy River basin is concentrated in the Eden Valley, with some farming on individual ranches along the Big Sandy River and Little Sandy Creek flood plains. The Eden Project is a large irrigation project located near Farson and Eden. This project includes approximately 17,000 acres of irrigated land. Water for irrigation comes from the Eden Valley and Big Sandy Reservoirs and from the Big Sandy River and Little Sandy Creek (fig. 9). Irrigation is done primarily by flooding. Logging in the northern part of the basin (fig. 9) is the other major land use in the area. Recreational activities, including hunting, fishing, and hiking, are popular. STREAMFLOW The Big Sandy River and Little Sandy Creek originate in the moun- tains where the greatest precipitation occurs and ground-water inflows sustain base flows. The major part of the annual runoff for these streams occurs during spring and early summer as a result of snowmelt. Late summer, fall, and winter flows are mainly the result of ground-water inflows. Daily discharge of the Big Sandy River at streamflow gaging stations upstream and downstream from the Big Sandy Reservoir are shown in figures 10 and 11. Many of the tributaries to the Big Sandy River and Little Sandy Creek originate in the plains area. These tributaries are ephemeral or intermittent; that is, they flow mainly in response to direct runoff from rainstorms or snowmelt. Only one streamflow-gaging station has been operated on an intermittent or ephemeral stream in the area. An average hydrograph for this station (09215000, Pacific Creek near Farson) is shown in figure 12. Small increases of streamflow occurring during the fall and winter months may be the result of storms that have occurred during individual years. The relative monthly distribution of the annual runoff in Pacific Creek is shown in figure 13. A comparison of the hydrographs for the Big Sandy River upstream (fig. 10) and downstream (fig. 11) from the Big Sandy Reservoir shows the decrease of high flows in the river caused by the reservoir and the irrigation project, particularly during May, June and July. The high flows during March and April at the station downstream from the Big Sandy Reservoir are caused by the early snowmelt on Pacific Creek and are unaffected by the reservoir. The monthly discharge for a common period of record for the two stations (fig. 14) further illustrates the change in flow characteristics due to the reservoir and show that the high flows have been reduced as would be expected. 12