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Table 1. 2, Water budget for the valley floor area of the Price River Basin (adapted from Hyatt et a1. 1970), Water (AF/yr) Salt (Tons/yr) Inflows Outflows Inflows Out flows Measured Surface 70,000 68,000 20,000 220,000 Unmeasured Surface 28,000 45,000 l\.,) Precipitation 15,000 0 Natural Loading 168,000 C)1 Agricultural Loading 15,000 Subsurface 4,000 28,000 I-' Phreatophyte Consumptive Use 5,000 Evapotranspiration from Soil 36,000 TOTAL 113,000 113,000 248,000 248,000 _._n___ Willardson et a1. (1979) published a chemical model of soll-irrigation water cation exchange. An application to the Ashley Valley of Utah examined the sensi- t ivity of streamflows and salinity to irri- gation water management alternatives and found the salinity of the streamflow to he most sensitive to increases in water con- veyance efficiency (canal lining). The effect of the lining, however, would depend on how the water saved was used. Peterson et a1. (1980) used experiments on the rate of salt release from Mancos Shale dedved salls to calibrate a chemical equilibrium model, derived from ion associa- tion theory, in interface with a kinetic model of salt release. The model was able to predict rates of salt release from sus- pended sediment. Narasimhan et a1. (1.980) reviewed development of the hydrosa1inity modeling art in terms of usefulness for water management decision making. They examined the assump- tions, approaches, data requirements, and applications for 17 existing models. Eigbt models portrayed water and salt movement down a stream or through a river basin by using steady-state relationships, treating salinity as a single conservative constituent (TnS), and using long time increments (generally months). Two models treat individual ions in the soil-water system, and four more integrate soil-water chemistry with solute transport. Finally, three models also reflect groundwater chemical reactions within the water or between the water and the aquifer. ~zdrosa1inity of the Price River Basin The Price River flows average (1931- 1960) 239,000 tons of salt and 71,800 acre- feet of water. According to Jeppson et al. (1968), the Price River contributes only 0,66 percent of the flow to the Colorado River at Lee Ferry while its salt contribution is 2.79 percent of the total. No other major tribu- tary of the Upper Colorado River has such a high salr to water ratio (about 2450 mg/1). Furthermore, Mundorff (1972) has noted that there are few identifiable point sources adding salinity to the Price River flow. Rather, the salt sour~es appear to be widely diffused over the basin and affect all major Price River tributaries. During average or low flow periods, salinity concentrations are bigh in all of them. On natural lands, weathering processes and vadous human activities expose soluble minerals at the ground surface. Rainfall causes runoff that dissolves some of these salts and erodes sediments that carry more. In addition the churning action grinds the sediments as overland flow collects in ephemeral channels, exposing more soluble minerals. Additional water infiltrates to interact with the soil in depos it ing and dissolving salts before emerging as interflow or groundwater discharge. Salts from all these sources (as well as from i rdgated lands) concentrate in the channels. Iorns et a1. (1965) indicated that the flow in the Price River alternately moves from the stream into the alluvium and back again. The interchange between water and alluvium deposits salts in the bed during low flow periods and contributes to the deterioration of water quality during high flows. In addition during high flows, additional salts enter the flow as channel banks erode and collapse into the stream. These banks may be particularly high in salt content where salts have been left behind by evaporation from seepage during low flow periods. During the growing season, the Price River is almost entirely diverted for irriga- tion of about 20,000 acres or about 8 percent of the valley area (see Figure 1.7), The principal canals serving the area are the Price-Wellington, Carbon, and the McFadden branch of the Cleveland Canal. Water in the latter is imported from Huntington Creek in the San Rafael River Basin. Estimates of the 8