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en 32,000 z ~ 28,000 ;;:; ci 24.000 N 9 20.000 t'.) en c 18,000 W ~ W;:. 12,000 '" w ~ MOO 0 en 4,000 en i5 ::; 0 :I: iz -4.000 0 ::Ii -MOO c w Iii -12.000 :J .., C .18,000 "f ~ -20.000 ..J u. -24,000 1978 STATION 09095500 STATION 09152500 STATION 09163500 "/ I / I II I II I/<~~""""""""""'"'''''''''''''''''''''''' / .... ....... " , , \ \ \ \ \ \ \ \ , .....................~:-:-:-................................. .......... ..... ........ ............ ............ 1980 1982 1984 1986 WATER YEAR 1988 1990 1992 1994 Figure 7. LOWESS smooth curves of flow-adjusted monthly dissolved-solids loads at stations 09095500 Colorado River near Cameo, 09152500 Gunnison River near Grand Junction, and 09163500 Colorado River near the Colorado-Utah State line, water years 1980-93. Trend results on the seasonal loads for August through October and November through February were variable (table 5). None of the trends in unadjusted seasonal loads for August through October were signif- icant (alpha 0.05). Trends in flow-adjusted loads for August through October were highly significant (decreasing loads with time) for station 09095500 for water years 1986-93 and for station 09152500 for 1970--93 (table 5). Although the flow-adjusted loads for August through October for the three test periods indicated decreasing loads with time for station 09163500, the p values of the trends were not significant. Trends in unadjusted dissolved-solids loads for November through February (table 5) were variable, and the most notable result is the highly significant downward trend in loads at station 09095500 for water years 1986-93. The trend in flow-adjusted load also was highly significant and downward for 1986-93 for station 09095500. The salinity-control projects in the Grand Valley primarily are designed to decrease the quantity of subsurface irrigation drainage, which is the mechanism of transport of irrigation-induced salinity to the Colorado River (Bureau of Reclamation, 1986). During the low-flow period of the year, a decrease in irrigation-drainage load from the Grand Valley might cause a trend in dissolved-solids loads at station 09163500 during November through February. Although the trend for the November through February loads was downward for 1986-93 at station 09163500, the trend was statistically not significant (table 5). As discussed with annual loads, the small sample size (eight values) for the seasonal data for 1986-93 make it more difficult to reject the null hypothesis of no trend. Grand Valley Dissolved-Solids Load The Grand Valley dissolved-solids load is the annual dissolved-solids load to the Colorado River from the Grand Valley (fig. 1), and at least 95 percent of that load was irrigation induced (Bureau of Reclamation, 1986). The trends in annual Grand Valley dissolved-solids load (table 1) were downward 20 Trend Analysla 01 Selected Water.Quallty Data Associated With Sallnlty-Control Projects In the Grand Valley, In the Lower Gunnison River Basin, and ~t Meeker Dome, Western Colorado