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Table 4.13, Analysis of salt dissolution rates for channel receiving no overland flow, N C> 00 ,.;::.. Degrees of Freedom Level of Significance Comparison t Statistic Estimated salt @ breakpoint Wet 8/26/76 to Dried 8/26/76 Wet 8/26/76 to Wet 9/9/76 Dried 8/26/76 to Wet 9/9/76 6 95 percent -4.59 6 6 0.570 NS 9S percent 7.262 Estimated salt @ It . 125 Wet 8/26/76 to Dried 8/26/76 Wet 8/26/76 to Wet 9/9/76 Dried 8/26/76 to Wet 9/9/76 -0.24 6 NS -0.46 6 NS 6 0.32 NS Null Hypothesis Ho: ~A = UB The collected data are listed in Ap- pendix C (Table C.9). Illustrative patterns of observed conductivity at four depths are shown on Figure 4.23 for the upper site (Figure 3.3). Conductivity slowly dropped with time from the initial 4000 )JIllhos/cm at 2S'C to less than 500 ~mhos/cm at 2S'C at 3 and 18 cm depths, and to less than 2000 ~mhos/cm at 2S'C at the 29 and 41 cm depths, respectively, a general trend toward higher conductivity at greater depth. Soil moisture tensions in the soil matrix were not monitored during these tests, and thus it is possible that the capacity of the sensors might have been exceeded. Under these conditions, a drop in the Boil moisture content below the saturation level would reduce the observed conductivity. The relatively slow changes in conduc- tivity indicate slow rates of salinity trans- port through the channel bed materisl. This observation was confirmed by permeability studies at four sites adjacent to Coal Creek. Four test holes were drilled to a defth of 1 meter at a horizontal distance 0 1 meter from the surface flow in Coal Creek. For each of the sites, no inflow to the holes was observed during the first 24 hours after dr illing. Discussion and Analysis of Results Although approximately 60 percent of the salt load passing Woodside originates in the mountainous areas of the Price River Basin, the joint effect of consumptive use reducing flows and salt loading on the valley floor multiplies salinity concentrations by over ten (Figure 4.5). Within the valley, three tributaries (Drunkards Wash, Desert Lake Wash, and Desert Seep Wash) are particularly high salt contributors to the Price River. The three streams contribute average daily salt loads of 518, 416, and 423 pounds per square mile of drainage area, respectively. Each stream drains irrigated farm land. Surveys of the valley floor suggested that subsurface inflows to the Price River account for a large portion of the total salt load originating in the valley. In contrast, longitudinal salt pickup from the mineral weathering of bed sediments in natural perennial channels was low in all the ob- served cases, irrespective of the salt concentration of the flowing water in the channel. From these findings, it is believed that the primary source of salinity in natural perennial streams with high salt concentra- tions is saline groundwater inflow. TDS va lues of 9000 mg/l and higher were observed in the field, and salt contents of some minerals may approach saturation. Where saturation occurs, TDS loadings are no longer additive, and salts are deposited, probably to be picked up later during high flow periods. Ion distributions would have to be considered in modeling salinity transport. Overland flow from storms occurred predominantly during the spring and summer months. Surface runoff was rapid, turbulent, and of short duration with little depression storage observed. A salinity profile of overland flow was not obtained. Within the main channel of Coal Creek, the longitudinal pickup of salt was low. Salt loading by groundwater inflow tended to be constant. Indigenous salts in the channel material of Coal Creek were heterogeneous with respect to mineral type and concentra- tion. Efflorescence density within the Coal Creek subbasin channel beds was also found to be highly variable, with observed densities ranging as high as 9000 gm/m2-cm. The source of the efflorescence seemed to be primarily evaporation of saline subsurface inflows to the channel. Laboratory jar tests on the Coal Creek channel sediments and shales indicated that mineral dissolution rates declined exponentially with time. This observation meshes with the observed low longitudinal salt uptake in perennial streams. Drying or turbulent mixing of the samples generally increased the rate of mineral dissolution. Channel salt pickup studies were con- ducted by supplying a sma 11 ephemeral tri- butary within the Coal Creek drainage with water from an irrigation ditch. The salinity pickup was found to decrease exponentially with time in this channel reach with low j 42