9623 - Laserfiche WebLink

Home Browse Search

References Cited 9 Table 4. Results of the seasonal Kendall test for trends on selected nutrient species in the Fraser River Basin, 1991 and 1995 through 2000. [mg/L, milligrams per liter; (mg/L)/yr, milligrams per liter per year; <, less than; --, no data] Site Site Span Number of Number of Minimum Data used p-value Trend Slope Median number name of trend analyses censored reporting in trend of tau direction [(mg/L)/yr] concentration (fig. 1) analysis analyses level analysis test (mg/L) (mg/L) Ammonia 3 Fraser River below Vasquez 1991-2000 108 22 < 0.002 Raw 0.0001 Down -0.002 0.018 Creek at Winter Park, CO 4 Fraser River at Tabernash, CO 1991-2000 108 10 < 0.002 Raw 0.1137 None 0.058 Flow-adjusted 0.4003 None Nitrite plus nitrate 1 Fraser River at Upper Station, 1995-2000 61 2 <0.005 Raw 0.0032 Up 0.0057 0.084 near Winter Park, CO Flow-adjusted 0.0238 Up 0.007 2 Fraser River below Buck 1991-2000 100 2 <0.005 Raw 0.0341 Down -0.0023 0.078 Creek at Winter Park, CO Flow-adjusted 0.1335 None 3 Fraser River below Vasquez 1991-2000 103 1 <0.010 Raw 0.2056 None 0.141 Creek at Winter Park, CO Flow-adjusted 0.9210 None 4 Fraser River at Tabernash, CO 1991-2000 105 1 <0.005 Raw 0.2255 None 0.174 Flow-adjusted 0.0414 Up 0.007 Orthophosphorus 3 Fraser River below Vasquez 1995-2000 61 7 <0.001 Raw 0.0125 Up 0.001 0.010 Creek at Winter Park, CO 4 Fraser River at Tabernash, CO 1995-2000 66 0 --- Raw 0.0076 Up 0.004 0.052 Flow-adjusted 0.0627 None Summary In general, the water in the Fraser River Basin is of good quality and compares favorably with State standards. A few pH values were greater than State standards, and even in these instances, the river was not out of compliance because of the limited number of exceedances. Un-ionized ammonia, nitrite plus nitrate, and chloride concentrations did not exceed any applicable State standard. Concentrations and loads of nutrients increased downstream; the largest inputs into the river were between Fraser River below Vasquez Creek at Winter Park (site 3) and Fraser River at Tabemash (site 4). Wastewater- treatment-plant discharges enter the Fraser River upstream from site 4. Median monthly loading data for nutrients and chloride indicate that the largest nutrient and chloride loading happens during early spring before the onset of spring runoff. Seasonal Kendall trend results indicate downward trends for ammonia concentration at Fraser River below Vasquez Creek at Winter Park (site 3) during the period of this study. Nitrite plus nitrate concentrations had upward trends at Fraser River at Tabernash (site 4) for the available data during 1995 through 2000. Results from the trend testing on nitrite plus nitrate concentrations during 1991 through 2000 at Fraser River below Buck Creek (site 2) had a downward trend and Fraser River at Tabernash (site 4) had an upward trend. Con- centrations of orthophosphorus showed consistently upward trends at both the Fraser River below Vasquez Creek at Winter Park and Fraser River at Tabernash sites. References Cited Apodaca, L.E., and Bails, J.B., 1999, Fraser River watershed, Colorado-Assessment of available water-quantity and water- quality data through water year 1997: U.S. Geological Survey Water-Resources Investigations Report 98-4255, 58 p. Cleveland, W.S., 1979, Robust locally weighted regression and smoothing scatterplots: Journal of the American Statistical Association, v. 74, p. 829-836. Colorado Water Quality Control Commission, 2001, June 30 (2001) Classifications and numeric standards for Upper Colorado River Basin and North Platte River (Planning Region 12) Regulation 33: Colorado Department of Public Health and Environment, Water Quality Control Commis- sion [variously paginated]. Colorado Water Quality Control Division, 1989, Colorado nonpoint assessment report: Denver, Colorado Department of Public Health and Environment, 189 p.