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l'V ~ o (7) inflow than salt outflow, implying a net deposit of salt in the valley. Desert Seep Wash drains agricultural lands and, at the gaging station, is more indicative of agricultural loading than of natural inflows. Hence, Desert Seep Wash was not modeled further. CHAPTER VII BASIN-WIDE HYDROSALINITY STUDY Introduction Narasimhan et al. (1980) compared a number of hydrosalinity models and concluded that the models generally suffer the weak- nesses of oversimplifications of 1) chemical processes, 2) surface-soil-groundwater interactions, and 3) salt pickup phenomena. Nevertheless, using one of the best of the available models, additional insight into water and salt flows within the Price River Basin was sought by applying BSAMl, developed by Huber et al. (1976). The model employs water and salt mass balance accounting on a monthly time interval through the representa- tion of the hydrologic system shown in Figure 7.1. In the application, only the runoff and salt fluxes from the valley bottom lands were cons idered. Data The BSAM modeling was based on the USGS gaging station near. Heiner, where Price River emerges from the' mountains onto the valley floor for water years 1973 through 1975. Since that station was discontinued in 1969, regression analyses were performed correlating flows for each month of the year at Heiner during the 1960s with recorded flows at USGS gages at Willow Creek, Beaver Creek, White River, and Scofield Reservoir (all of which are upstream of Heiner--see Figure 1.1). During the winter months, only flows at Willow Creek and Scofield Reservoir were used because of inaccurate or incom- plete records at the other two stations. Many combinations of recorded flow records were examined. The highest correlations are tabulated in Table 7.1. Precipitation ,and temperature data from the weather stations at Hiawatha, Sunnyside, and Price Warehouse were also used as input data for BSAM. These stations are scattered within the basin and provide fairly repre- sentative temperature data. More precipita- t ion gages would have been helpful. I t is apparent from an examination of precipita- tion and streamflow records that localized thunderstorms causing significant runoff may miss all three precipitation gages. This causes error in the calibration of the model. Gordon Creek and Desert Seep Wash, two major tributaries of the Price River, were modeled to estimate ungaged surface inflows of water and salt. These runs proved un- satisfactory in that there was more salt Records in the State Engineer's office were examined for canal diversion data. Canal water imported from the San Rafael Basin is not measured, and this quantity, therefore, was estimated from the irrigated acreage served. Estimates of groundwater inflow were taken from Cordova (1964). Results The match with recorded data achieved in calibrating BSAMl to Price River flows at woodside is portrayed for water flow (Figure 7.2), total salt flow (Figure 7.3), and salt concentration (Figure 7.4). BSAMl models total salt outflow from the basin by summing loadings from various sources. The amount of salt loading indicated by the model as coming from agricultural lands suggest them to be a major salt source in the Price River Basin. Of the apptoximately 190,000 tons of salt leaving the basin at Woodside annually during the calibration peri~d, about 76,000 tons or 40 percent originated within the central basin. Model results also indicate that about 3,500 tons originated with ungaged overland flow and pickup by channel process- es. These figures agree closely with the estimates given in Chapter VI. The remaining 72,500 tons of salt originating annually within the central basin are from surface agricultural return flows and groundwater inflows to the Price River. Agriculture is thus an important salt source. Approximately 114,000 tons of salt were modeled during 1973-1975 as entering the central portion of the basin in approximately 120,000 acre-feet of water (average TDS approximately 700 mgfl), but only about 75,000 acre-feet of water were modeled leaving the basin. Even without any salt pickup in the basin, the outgoing TDS would be about 1100 mgfl--a significant increase from the 700 mgfl--just from concen- tration effects caused by evapotranspiration. A large portion of this loss is from agri- cultural crops. Model results indicate that irrigation efficiencies in the valley are fairly high-- 65