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<br />There were statistically significant downward
<br />trends during water years 1986-93 in the Colorado
<br />River near the State line (station 09163500) for flow-
<br />adjusted dissolved-solids, magnesium, sodium, and
<br />sulfate concentrations and flow-adjusted monthly
<br />and annual dissolved-solids loads. The cumulative
<br />effects of salinily-control proje.cts in the Grand Valley
<br />and the lower Gunnison River Basin on dissolved
<br />solids in the Colorado River would have become more
<br />pronounced after the mid- 1980's. The decreasing
<br />constituent concentrations and dissolved-solids
<br />loads at station 09] 63500 for 1986-93 also were
<br />reported for the Colorado Ri ver near Cameo
<br />(station 09095500), which is upstream from the
<br />salinity-control projects. Some of the decreases in
<br />dissolved solids at station 09163500 may have resulted
<br />from decreases in dissolved solids in the Colorado
<br />River at station 09095500. Apparently, there are natu-
<br />ral or man-induced effects in the Upper Colorado River
<br />Basin that may be related to the trends of decreasing
<br />salinity in the Colorado River near Cameo. Compari-
<br />son of trend slopes for annual dissolved-solids loads
<br />indicated that some of the decrease in dissolved-solids
<br />loads in the Colorado River near the Stale line since
<br />1986 probably were related to salinity-control projects
<br />in the Grand Valley and in the lower Gunnison River
<br />Basin.
<br />
<br />Step-trend tests on chloride and sodium data col-
<br />lected at three gaging stations on the White River in the
<br />vicinity of Meeker Dome were used to verify that plug-
<br />ging of three wells on Meeker Dome in 1980-81 was
<br />effective in decreasing the discharge of saline ground
<br />water from the leaking wells and to verify that the well
<br />plugging had remained intact through early 1995.
<br />Multiple t-tests were done on concentrations and on
<br />ranks of the concentrations to compare chloride and
<br />sodium data collected before and after the well plug-
<br />ging. Also, flow-adjusted chloride and sodium concen-
<br />trations were tested using ESTREND. Chloride and
<br />sodium concentrations have remained relatively
<br />unchanged from water years 1973 to 1995 in the White
<br />River above Coal Creek, which is upstream from
<br />Meeker Dome. At two slations downstream from
<br />Meeker Dome, White River at Meeker and White River
<br />below Meeker, chloride and sodium concentrations had
<br />highly significant (significance level less than 0.01)
<br />decreases after the well plugging was completed.
<br />Chloride and sodium concentrations have not changed
<br />significantly since April 1982 in the White River
<br />downstream from Meeker Dome, indicating that the
<br />well plugging has remained intact.
<br />
<br />REFERENCES CITED
<br />
<br />Bureau of Reclamation, 1982, Lower Gunnison Basin Unit,
<br />feasibility report-Appendix B, Hydrosalinity: Salt
<br />Lake City, Utah, Upper Colorado Region, 86 p.
<br />-1983, Grand Valley salt pickup calculations, Colorado
<br />River Basin Salinity Control Project: Grand Junction,
<br />Colo. [three sections plus appendixes].
<br />-1984, Lower Gunnison Basin Unit, feasibility
<br />report/final environmental statement: Salt Lake City,
<br />Utah, Upper Colorado Region, 204 p.
<br />-1985a, Grand Valley Unit, Stage Two development,
<br />final environmental impact statement: Bureau of
<br />Reclamation Report INT FES86-1O, 217 p.
<br />-1985b, Planning report, concluding the study on
<br />Meeker Dome Unit, Colorado: Salt Lake City, Utah,
<br />Upper Colorado Region, 35 p.
<br />-1986, Colorado River Basin Salinity Control Project,
<br />Grand Valley Unit-Stage Two development, water
<br />resources technical supporting data for the verification
<br />memorandum, April 1986: Salt Lake City, Utah,
<br />Upper Colorado Region [8 chapters].
<br />-1987, Lower Gunnison Basin Unit-Winter water:
<br />Salt Lake City, Utah, Colorado River Water Quality
<br />Improvement Program Preconstruction Report, 57 p.
<br />-1994. Lower Gunnison Basin Unit-East side later-
<br />als: Salt Lake City, Utah, Colorado River Water
<br />Quality Improvement Program, 51 p. [supplement to
<br />the feasibility report].
<br />Butler, D.L., Wright, W.G., Hahn, D.G., Krueger, R.P.,
<br />and Osmundson, B.C., 1994, Physical, chemical,
<br />and biological data for the detailed study of irrigation
<br />drainage in the Uncompahgre Project area and in
<br />the Grand Valley, west-central Colorado, 1991-92:
<br />U.S. Geological Survey Open-File Report 94-110,
<br />146 p.
<br />CH2M Hill, 1979, Problem identification and quantification,
<br />Meeker Dome salinity investigation: Denver, Colo.
<br />[four numbered sections plus appendixes].
<br />-1982, Phase I report, salinity investigation of the
<br />Meeker Dome Unil: Denver. Colo. [nine numbered
<br />sections].
<br />Cleveland, W.S., 1979, Robust locally weighted regression
<br />and smoothing scatterplots: Journal of American
<br />Statistical Association, v. 74, no. 368, p. 829-836.
<br />Hedlund, J.D.. 1994, Water and salt budgets: Portland, Ore.,
<br />U.S. Department of Agriculture, Soil Conservation
<br />Service, West National Technical Center, 60 p.
<br />Helsel, DR, and Hirsch, R.M., 1992, Statistical methods
<br />in water resources: Amsterdam, Elsevier Science
<br />Publishers, 529 p.
<br />Hirsch, R.M., Alexander, R.B., and Smith, R.A., 1991,
<br />Selection of methods for the detection and estimation
<br />of trends in water quality: Water Resources Research,
<br />v. 27, no. 5, p. 803-813.
<br />
<br />REFERENCES CITED 37
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