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<br />3. Flows in the open drains in the <br />Uintah Basin exhibit a high degree of spatial <br />variability. When the flow of water reduced <br />sharply to 0.5 - 2.0 gpm, however, there was <br />a sharp increase in the EC, suggesting an <br />important base flow contribution to total <br />salinity in the drains. The scatter of the <br />concentrations in the larger flows (Figure <br />2.7) suggests that one should consider the <br />possibility of using spatial variability in <br />TSC values when modeling a basin like the <br />U intah. <br /> <br />4. A plot of salt outflow versus total <br />drainage outflow for the Grand Valley drains <br />(Figure 2.8) displays considerable scatter. <br />The pattern, however, generally fits an <br />hypothesis that groundwaters contributing <br />about 20 tons/day per cfs (7420 ppm) mixes\ <br />with variable amounts of surface and irriga- "" <br />t ion water causing the scatter.ed points to "':, <br />the right. The 7420 ppm is the approximate <br />slope of an envelope curve on the left side <br />of the plot. From these trends, two hypothe- <br />ses provide reasonable assumptions for <br />modeling the salt loading of drainage flow. <br /> <br /> LEGEND EC <br /> Z 1. FEATHER RIVER WATER 0.10 <br /> 0 <br />W j:: 2. GRAND RIVER WATER 0.94 <br />W ::l 3, MISSOURI RIVER WATER 0,91 <br /> -' 4, SALT RIVER WATER 1.56 <br />W 0 5, COLORADO RIVER WATER 1. 27 <br /> (J) <br />-.:1 (J) 6. SEVIER RIVER WATER 2,03 <br /> 0 7. GILA RIVER WATER 3.14 <br /> >- 20 8, PECOS RIVER WATER 3,26 <br /> <Xl <br /> (J) <br /> ':i <br /> <l <br /> ~ (J) @ <br /> (/)lL <br /> _0 10 G) <br /> (/)z <br /> <(<l <br /> CO", <br /> 0"+ (g) <br /> Wz (f) <br /> ::!: 0 @ <br /> ~ z <br /> 0 (?) <br /> j:: <br /> (/) ~ <br /> Z <br /> 0 a. @ <br /> !c( U -10 <br /> w <br /> a: <br /> U a. <br /> U. ~ <br /> 0 (J) <br /> ::!: ':i -20 <br /> <l <br /> ::> (J) <br /> (/) lL <br /> 0 <br /> (J) <br /> (J) <br /> 9 -30 <br /> I- <br /> w <br /> z <br /> <br /> <br />-40 <br />0.10 <br /> <br />0.15 <br /> <br /> <br />0,20 <br /> <br />0,25 <br /> <br />0,30 <br /> <br />LEACHING FRACTION, LF <br /> <br />Figure 2,4. Net contribution of mineral weathering and salt precipitation expressed as per- <br />cent of salts applied in irrigation waters in noncalcarious soils. (After <br />Rhoades et a1, 1974,) <br /> <br />9 <br /> <br />