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0019c:7 BAUCH & SPAHR: SALINITY TRENDS IN SURFACE WATERS OF TIlE COLORADO RIVER BASIN 647 Table 4. Trends in flow-adjusted monthly dissolved-solids loads, Upper Colorado River Basin in Colorado, water years 1970 to 1993, 1980 to 1993, 1986 to 1993. Number after site name refers to site number in Fig. 1. Data for Colorado River near Cameo and Gunnison River at Grand Junction from Butler (1996). Trend Site Period Slope Percent P value SL direction Colorado River Basin Upstream from Cameo, CO Colorado River at Hot Sulphur Springs (2) 1970-1993 - 2.24 -0.15 <0.001 HS Down 19110-1993 3.72 0.26 0.005 HS Up 1986-1993 -11.60 -0.93 <0.001 HS Down Muddy Creek at Kremmling (3) 1986-1993 0.972 NS None Rock Creek at Crater (4) 1986-1993 -2.72 -1.89 <0.001 US Down Eagle River at Gypsum (5) 1970-1993 -70.60 -0.54 <0.001 HS Down 1980--1993 -99.70 -0.76 <0.001 HS Down 1986-1993 -166.00 -L41 <0.001 HS Down Colorado River near Dotsero (6) 1970-1993 - 211.00 -0.61 <0.001 HS Down 19110-1993 -66.30 -0.20 0.005 HS Down 1986-1993 266.00 0.79 <0.001 US Up Colorado River above Glenwood Springs (7) 1970-1993 ,0.715 NS None 19110-1993 0.862 NS None 1986-1993 -382.00 -0.87 <0.001 HS Down Roaring Fork River at mouth (8) 1970-1993 -105.00 -0.40 <0.001 HS Down 1980--1993 -61.50 -0.23 <0.001 HS Down 1986-1993 0.125 NS None Colorado River near Cameo (9) 1970-1993 - 333.00 -0.27 <0.001 HS Down 19110-1993 -687.00 -0.55, 0.001 US Down 1986-1993 - 3840.00 -3.31 0.001 HS Down Gunnison River Basin Taylor River at Almont (10) 1970-1992 -2.85 -0.14 <0.001 HS Down 19110-1992 0.299 NS None 1986-1992 8.75 0.46 <0.001 US Up East River at conOuence with Taylor River (11) 1970-1991 -1.24 -0.03 0.016 S Down 1980-1991 -7.44 -0.20 <0.001 US Down 1986-1991 - 25.00 -0.74 <0.001 HS Down Uncompahgre River at Delta (12) 1970-1993 -198.00 -0.71 <0.001 HS Down 19110-1993 0.190 NS None 1986-1993 268.00 1.05 <0.001 HS Up Gunuison River at Grand Junction (13) 1970-1993 -451.00 -0.61 <0.001 HS Down 1980--1993 0.201 NS None 1986-1993 0.592 NS None Periods are in water years; slopes are in milligrams per liter per year, percent is the slope expressed as percent change per year, P value is the significance level of the test; SL is significance level; levels are: US = highly significant, P :s; 0.01; S = significant, P > 0.01 and :s; 0.05; MS = marginally significant, P > 0.05 and :s; 0.10; and NS = not significant, P > 0.10. monthly loads was indicated for one site (Site 7) for this time period. For 1980 to 1993, monthly loads at three upstream sites had significant downward trends, whereas loads at one site (Site 2) had an upward trend and loads at one site (Site 7) had no trend. The latter two sites were on the main-stem, as was one of the sites with a downward trend. Similar trend results to 1980 to 1993 were determined for loads at the upstream sites for 1986 to 1993, except that two of the main-stem sites had significant downward trends and the other main- stem site had a significant upward trend. Annual Loads. For flow-adjusted annual dissolved- solids loads, no trends were reported by Butler (1996) for the Colorado near Cameo site (Site 9) for 1970 to 1993 or 1980 to 1993, but a significant downward trend in annual loads was indicated for 1986 to 1993 (Table 5). Upstream from Cameo, loads at three sites had sig- nificant downward trends for 1970 to 1993, whereas trends were not detected for two sites, both on the main- stem Colorado River (Table 5 and Fig. 6). For 1980 to 1993, a significant downward trend in annual loads was reported for one main-stem site (site 6), whereas trends were not indicated for the other four upstream sites. Loads at five of the seven sites upstream from Cameo, including the three on the main-stem Colorado River, had significant downward trends reported for 1986 to 1993. Loads at the remaining two sites had no trends. The percent decrease in flow-adjusted annual loads ranged from 0.25 at the mouth of the Roaring. Fork River to 3.83 for Rock Creek at Crater (Table 5). The greatest percent decreases occurred mainly during the 1986 to 1993 analysis period. Annual loads for the Colo- rado River near Cameo site decreased 2.95% per year between 1986 and 1993, whereas the decrease for the site Colorado River above Glenwood Springs (site 7) was 1.77% per year for 1986 to 1993. Gunnison River Basin Concentrations. In the Gunnison River Basin, most trend results for periodic dissolved-solids concentra- tions were not statistically significant (Table 3). Of the 12 site/analysis-period combinations, two had trend re- sults indicating decreasing periodic dissolved-solids con- centrations, and another two had results indicating in- creasing concentrations (Fig. 4). The two significant downward trends occurred in 1970 to 1993, whereas the upward trends occurred in 1986 to 1991 and 1986 to 1993.