9521 - Laserfiche WebLink

Home Browse Search

season, calcium, sulfate, and bicarbonate are all equally dominant. Before the Meeker well was plugged, sodium also was a predominant cation during low flow. The period of record was divided into a preintervention period (1951-68) and a postintervention period (1969-83), based on the plugging of the Meeker well in October 1968. Annual step-trend analyses indicated a highly significant decrease in annual dissolved-solids concentration of 89 mg/L (table 4). This trend represents a 19-percent decrease from the preintervention median concentration. Dissolved sodium and chloride make up 55 percent of the total decrease. No significant annual monotonic trends were identified for either the preintervention or postintervention periods. Bitter Creek at Mouth, near Bonanza, Utah (site 51) Bitter Creek, like Evacuation Creek, drains the Green River and Uinta Formations in the Uinta Basin. Bitter Creek is the largest single inflow to the White River downstream from site 50. Streamflow at site 51 (table 3, pl. 1) is very small, mostly occurring as surface runoff from summer thunderstorms. The mean annual flow-weighted dissolved- solids concentration is 6,740 mg/L (table 7), the highest of the 70 sites used for this report. Eighty-six percent of the mean-annual dissolved-solids load is dissolved sodium and sulfate. White River at Mouth, near Ouray, Utah (site 52) During 1975-83, the White River had an average an- nual net accumulation of about 11,000 acre-ft of streamflow and 40,000 tons of dissolved solids between site 50 and site 52 (table 3, pl. 1). Almost all of the increased dissolved- solids load was composed of sodium, sulfate, and bicarbonate from Bitter Creek and other small streams. The composi- tion is predominantly calcium and bicarbonate during the high-flow season and sodium, calcium, sulfate, and bicar- bonate during the low-flow season. Mean annual flow- weighted dissolved-solids concentration is 419 mg/L (table 7), which is less than at site 34 (491 mg/L) but is considerably greater than upstream on the Green River at site 38 (152 mg/L). Lower Green Subregion The lower Green subregion includes the drainages of the Price and San Rafael Rivers and all other tributaries to the Green River between the confluence of the White and Green Rivers and the confluence of the Green River with the Colorado River. About 41,000 acres is irrigated in the Price River basin, mainly near the town of Price, Utah. Runoff from the Wasatch Plateau is stored in Scofield Reser- voir for irrigation releases, and some water is diverted into the Price River basin from Huntington Creek in the San Rafael River basin. Mancos Shale deposits underlie much of the agricultural area in the lower Price River basin and contribute large quantities of dissolved solids to the Price River. Accumulation of salts in agricultural land is a serious issue. Coking coal is produced in the Price River basin from underground mines; however, production declined during the 1960's and early 1970's (Mundorff, 1972). The San Rafael River basin shares many characteristics with the Price River basin. It is very and except for the head- waters in the Wasatch Plateau. About 42,000 acres is irri- gated, primarily on Mancos Shale benches, in the vicinity of the towns of Huntington, Castle Dale, and Ferron, Utah (pl. 1). Water is stored for irrigation release in Joes Valley Reservoir and Electric Lake. Coal-fired powerplants in Emery County, Utah, use an estimated 24,000 acre-ft of water per year. There are many small transbasin exports westward to the Great Basin that date back to 1906. Down- stream from the agricultural lands, the San Rafael River crosses the San Rafael Swell, an uplift area where upper Paleozoic and Mesozoic strata are exposed. These include the Curtis and Carmel Formations of Jurassic age, which con- tain deposits of gypsum and halite. Price River at Woodside, Utah (site 53) Streamflow at site 53 (table 3, pl. 1) is greatly affected by storage, diversions for public supply and agriculture, and irrigation-return flows. Water seldom is released from Scofield Reservoir during the winter, and the growing-season releases ordinarily are used entirely for irrigation. Because of irrigation diversions, median daily streamflow at site 53 lacks a snowmelt-runoff peak (fig. 20A). Occasional extreme- runoff years, when snowmelt greatly exceeds irrigation requirements, cause an increase in mean daily streamflow during April through June. Summer and autumn storms pro- duce flash floods that have peak flows as large as 5,000 ft3/s. Mean annual dissolved-solids load averages 240,000 tons (table 7), of which 76 percent is dissolved sodium and sulfate. During 1949-83, the mean annual flow-weighted dissolved- solids concentration was 1,990 mg/L (table 7). Sodium and sulfate are the predominant ions throughout the year, prob- ably because of fairly continuous irrigation-return flows from the agricultural areas. For 1949-83, annual monotonic-trend analyses indi- cated a significant decrease in median annual dissolved-solids concentration of 33.2 mg/L per year and a highly signifi- cant decrease in median annual flow-adjusted concentration of 23.1 mg/L per year (table 8). Decreases occurred during all months and for all constituents except dissolved bicar- bonate, which is not strongly affected by contributions from the Mancos Shale. The decrease in dissolved-solids concen- tration represents a 37-percent change in the median annual concentration and may result from agricultural lands that have been taken out of production. The decrease in flow-adjusted concentration represents a 28-percent change in the median annual flow-adjusted concentration during the period of record. About 89 percent of this change was due to decreases in sodium and sulfate concentrations. Dissolved-solids load did not change significantly. 46 Characteristics and Trends of Streamflow and Dissolved Solids in the Colorado River Basin