Water-Quality Characteristics and Ground-Water Quantity
<br />of the Fraser River Watershed, Grand County, Colorado,
<br />1998-2001
<br />Nancy J. Bauch and Jeffrey B. Bails
<br />Abstract
<br />The U.S. Geological Survey, in cooperation with the
<br />Grand County Board of County Commissioners, conducted a
<br />4-year study to assess ground- and surface-water-quality condi-
<br />tions and ground-water quantity in the 302-square-mile Fraser
<br />River watershed in north-central Colorado. The Fraser River
<br />flows north about 28 miles from the headwaters near the Conti-
<br />nental Divide, through the towns of Winter Park, Fraser, Taber-
<br />nash, and Granby, and is one of the major tributaries to the
<br />Upper Colorado River. Increasing urban development, as well
<br />as the seasonal influx of tourists, is placing more demands on
<br />the water resources in the Fraser River watershed.
<br />A ground-water sampling network of I 1 wells was
<br />established to represent different aquifer systems (alluvial,
<br />Troublesome Formation, Precambrian granite), land uses
<br />(urban, nonurban), and areas with or without individual septic
<br />disposal system use. The well network was sampled for ground-
<br />water quality on a semiannual basis from August 1998 through
<br />September 2001. The sampling included field properties and the
<br />collection of water samples for analysis of major ions, trace
<br />elements, nutrients, dissolved organic carbon, bacteria, methyl-
<br />ene blue active substances, and radon-222. One surface-water
<br />site, on the Fraser River just downstream from the town of
<br />Tabernash, Colorado, was sampled bimonthly from August
<br />1998 through September 2001 to assess the cumulative effects
<br />of natural and human processes on water quality in the upper
<br />part of the Fraser River watershed. Surface-water-quality sam-
<br />pling included field properties and the collection of water-qual-
<br />ity samples for analysis of major ions, trace elements, nutrients,
<br />organic carbon, and bacteria.
<br />Ground water was a calcium-bicarbonate type water and is
<br />suitable as a drinking-water, domestic, municipal, industrial,
<br />and irriuation source. In general, no widespread ground-water-
<br />quality problems were indicated. All pH values and concentra-
<br />tions of dissolved solids, chloride, fluoride, sulfate, nitrite, and
<br />nitrate in the ground-water samples met or were substantially
<br />less than U.S. Environmental Protection Agency drinking-
<br />water standards and health advisories or State of Colorado
<br />water-quality standards. Federal standards for turbidity and
<br />concentrations of iron, manganese, methylene blue active sub-
<br />stances, and radon-222 were not met in water samples from at
<br />least one well. The only ground-water-quality concern assessed
<br />by this study is radon-222, which was detected in all radon-
<br />analyzed samples from 10 wells at levels exceeding the pro-
<br />posed U.S. Environmental Protection Agency drinking-water
<br />standard of 300 picocuries per liter.
<br />Concentrations of chloride, magnesium, and sulfate were
<br />statistically different (higher) in ground-water samples from
<br />wells completed in the alluvial aquifer, urbanized areas, and
<br />areas with individual septic disposal system use than those from
<br />wells completed in the Troublesome Formation, nonurban
<br />areas, and areas without individual septic disposal system use.
<br />Dissolved organic carbon concentrations were statistically
<br />higher in ground-water samples from wells completed in the
<br />alluvial aquifer and areas without individual septic disposal sys-
<br />tem use than those from wells completed in the Troublesome
<br />Formation and areas with individual septic disposal system use.
<br />Differences in dissolved organic-carbon concentrations
<br />between the latter category and areas without septic systems
<br />likely had no environmental significance.
<br />Surface water at the site Fraser River below Crooked
<br />Creek at Tabernash was a calcium-bicarbonate type water and
<br />is suitable as a drinking-water, residential, commercial, and irri-
<br />gation resource. All pH values and concentrations of dissolved
<br />oxygen were within the State of Colorado instream water-qual-
<br />ity standards, and all concentrations of chloride, sulfate, iron,
<br />manganese, un-ionized ammonia, nitrite, nitrate, and fecal
<br />coliform bacteria met State standards. Seasonal changes in the
<br />values or concentrations of field properties and constituents in
<br />the surface water were detected. For most constituents, maxi-
<br />mum concentrations typically occurred during winter with low
<br />streamflow conditions, and minimums typically occurred dur-
<br />ing spring as a result of dilution by snowmelt runoff.
<br />Ground-water quantity was estimated for the alluvial and
<br />Troublesome Formation aquifers in the upper portion of the
<br />Fraser River watershed, the most likely area for future ground-
<br />water use. The estimated average volume of available ground
<br />water in the alluvial aquifer was about 150,000 acre-feet, with
<br />seasonal fluctuations of about 7 percent. The Troublesome
<br />Formation aquifer, which consists of siltstone and interbedded
<br />sandstone and conglomerate, has approximately 370,000 acre-
<br />feet of available water in the upper 500 feet of the aquifer.
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