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Introduction 3 the Fraser River itself (Bails, 2003), little historical information is available on ground- and surface-water quality in the Fraser River watershed. An assessment of available water-quality data in the watershed through water year 1997 revealed few ground- and surface-water-quality data (Apodaca and Bails, 1999). The effects of population growth and the conversion of rangeland and forests to urban land uses on ground-water quality in the Fraser River watershed were first studied in 1997 as part of the Upper Colorado River Basin study unit of the U.S. Geological Survey (USGS) National Water-Quality Assessment Program (Apodaca and Bails, 2000; Apodaca and others, 2002). Recognizing the lack of baseline water-quality data for the Fraser River watershed, the Grand County Board of County Commissioners indicated a need to further characterize and monitor water quality in the watershed. In 1998, the USGS, in cooperation with the Grand County Board of County Commissioners, began a detailed water-quality study in the area. The objectives of the study were to (1) assess current ground-water quality and quantity in areas with present-day development and potential future development in the Fraser River watershed, (2) determine the effects of individual septic disposal systems (ISDS's) on ground-water quality, and (3) assess current surface-water quality and quantity at a site on the Fraser River downstream from the town of Tabernash to determine the effects of present-day growth in the watershed and to support assessment of future growth. This study provides baseline ground- and surface-water information for the Fraser River watershed. Water-quality sampling began in August 1998 and continued through September 2001. Results from the initial sampling in August 1998 relating the effects of ISDS's on ground-water quality were described by Apodaca and others (2000). Purpose and Scope This report presents an assessment of ground- and surface- water-quality data and ground-water-quantity data collected by the USGS from August 1998 through September 2001 in the Fraser River watershed. Ground-water-quality data include field properties and concentrations of dissolved solids, major ions, selected trace elements, nutrients, organic carbon, bacte- ria, methylene blue active substances (MBAS), and radon-222 for water from 1 1 wells. These data are related to aquifer type (alluvial, Troublesome Formation), land use (urban, nonurban), and location in ISDS and non-ISDS areas. Ground-water- quality data also are examined for changes over time. The sur- face-water data include field properties and concentrations of dissolved solids, major ions, selected trace elements, nutrients, organic carbon, and fecal coliform bacteria for water from one site on the Fraser River. This report also presents an estimate of the quantity of water available in the alluvial aquifer of the Fraser River and in the Troublesome Formation. Description of the Fraser River Watershed The Fraser River watershed is in north-central Colorado in Grand County (fig. 1) and lies within the Southern Rocky Mountains physiographic province (Hunt, 1974). The water- shed comprises about 302 mil in the southeastern part of Grand County and constitutes about 16 percent of the total area (1,869 mi-) of the county. The terrain within the watershed is flat in the valleys to mountainous in the southern and eastern boundaries, with land-surface altitudes ranging between about 8,000 and 12,800 ft. The Fraser River flows northerly about 28 mi from its headwaters along the Continental Divide in the Arapaho National Forest though the towns of Winter Park, Fraser, Tabernash, and Granby to its confluence with the Colo- rado River (fig. 1). The primary tributaries to the Fraser River are Vasquez, St. Louis, Crooked, Ranch, Tenmile, and Straw- berry Creeks (fig. 1). Land use/land cover in the Fraser River watershed is 64 percent evergreen forest; 8 percent deciduous forest; 24 per- cent pasture, shrubland, and grassland; less than 2 percent urban, less than 2 percent perennial ice/snow or bare rock; and less than 1 percent open water (fig. 2) (U.S. Environmental Pro- tection Agency, 2002a). For purposes of this report, the land use/land cover is classified as "urban" or "nonurban" (forests, rangeland, grassland) and "ISDS" or "non-ISDS" area, based on a visual examination of land use around a well and well loca- tion in an area of historical or new ISDS use or in an area with- out ISDS use. Daily average temperature ranges between 13°F and 55°F. Average annual precipitation ranges from 20 inches per year north and west of Fraser to more than 40 inches per year in the higher peaks along the Continental Divide in the eastern and southern portions of the watershed. The geology of the Fraser River watershed varies from rocks of Precambrian age to unconsolidated alluvium of Qua- ternary age (fig. 3). Igneous and metamorphic rocks (granite, gneiss, and schist) of Precambrian age are exposed in the north- eastern, eastern, and southern areas of the watershed. Fractured rocks of this age generally produce small quantities of water that are suitable only for domestic uses. Sedimentary rocks of Triassic, Jurassic, and Cretaceous age in the northwestern area of the watershed yield little water, however, yields probably are sufficient for most domestic purposes. Rocks of Tertiary age or younger, including the Troublesome Formation and alluvium, have the largest yields for wells in the watershed (Voegeli, 1965). The Troublesome Formation of Tertiary age is primarily siltstone with some interbedded sandstones and conglomerates and is as much as 1,000 ft thick. Alluvium consists of unconsol- idated sand and gravel and glacial drift and is as much as 200 ft thick. Recharge is derived mostly from snowmelt (Apodaca and others, 2000). Aquifers in the Fraser River watershed include the alluvial aquifer composed of alluvium, the Troublesome Formation aquifer composed of rocks of the Troublesome Formation, and the Precambrian granite aquifer composed of fractured granite.