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4 Streamwater Quality at Selected Sites in the Fraser River Basin, Grand County, Colorado, Water Years 1991-2000 Table 3. Summary of median concentrations of selected water-quality constituents at 13 sites in the Fraser River Basin, 1991-2000. [mg/L, milligrams per liter] Site Site Chloride Ammonia Nitrite Dissolved Ortho- Total number name (mg/L) (mg/L) plus nitrate phosphorus phosphorus phosphorus (fig. 1) (mg/L) (mg/L) (mg/L) (mg/L) 1 Fraser River at Upper Station, near 9.782 0.002 0.084 0.003 0.001 0.050 Winter Park, CO 2 Fraser River below Buck Creek at 8.370 0.003 0.075 0.004 0.002 0.050 Winter Park, CO 3 Fraser River below Vasquez Creek 5.40 0.018 0.127 0.012 0.009 0.050 at Winter Park, CO 4 Fraser River at Tabernash, CO 4.835 0.065 0.169 0.062 0.051 0.102 5 Fraser River below Crooked Creek 3.48 0.034 0.085 0.031 0.027 0.059 at Tabernash, CO 6 Fraser River at Highway 40 at 4.010 0.030 0.140 0.040 0.040 0.060 Granby, CO 7 Crooked Creek below Tipperary Creek 0.280 0.004 0.006 0.007 0.005 0.041 near Tabernash, CO 8 Crooked Creek above Pole Creek at 2.915 0.007 0.005 0.015 0.010 0.041 Tabemash, CO 9 Pole Creek at Upper Station near 0.380 0.005 0.008 0.017 0.013 0.050 Tabernash, CO 10 Pole Creek at mouth near Tabernash, CO 2.04 0.008 0.025 0.021 0.017 0.051 11 Ranch Creek near Fraser, CO 0.251 0.002 0.033 0.004 0.003 0.030 12 Hurd Creek below Trail Creek near 0.405 0.004 0.005 0.004 0.002 0.050 Tabernash, CO 13 Ranch Creek below Meadow Creek 0.515 0.003 0.035 0.012 0.007 0.050 near Tabernash, CO Water samples were analyzed for dissolved chloride, dis- solved or total ammonia, dissolved or total nitrite plus nitrate, dissolved and total phosphorus, dissolved orthophosphorus, and fecal coliform bacteria. Properties measured at the time of sample collection include water temperature, pH, specific conductance, and dissolved oxygen. The dissolved phase of water-quality constituents was obtained by filtering sampled water through a 0.45-µm (micrometer) filter; total concentra- tions are from unfiltered samples. Nutrient samples (ammonia, nitrite plus nitrate, phosphorus, and orthophosphorus) col- lected in the Fraser River Basin from October 1991 through September 2000 were analyzed for either total or dissolved concentrations. In general, most samples collected before cal- endar year 1992 were analyzed for total nutrients. From water year 1993 through 2000, water-quality samples were analyzed for dissolved nutrients. Total and dissolved concentrations only were determined for phosphorus from samples collected for the same sampling event. At sites where total and dissolved nutrient samples were collected over time, the data were aggregated for statistical analysis using the methods outlined in Mueller and others (1995). Unless otherwise specified, con- centrations in this report represent aggregated concentrations. Streamwater-Quality Results Stream Standards Specific properties and constituents compared to appli- cable State standards include pH, dissolved oxygen, fecal coliform bacteria, un-ionized ammonia, nitrite plus nitrate, and chloride. A summary of water-quality data for selected con- stituents is in tables 2 and 3. Analysis of the data for this report indicates that water quality in the Fraser River Basin is gener- ally very good and compares favorably to State standards. In general, pH measurements from the study sites were within the State standard range of 6.5-9. At site 4, the pH measurements were greater than the maximum State standard for less than 10 percent (29) of the total number (307) of mea- surements taken. Compliance with State standards, however, is determined by comparing the 15th and 85th percentiles of the representative water-quality data with the associated water-quality standard. For site 4, the 15th and 85th percentile values for pH were equal to 7.6 and 8.8, respectively, which is