Scientific Investigations Report 2006-5238
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AbstractThis report presents the results of a study conducted by the U.S. Geological Survey, in cooperation with the North Dakota State Water Commission, the Devils Lake Basin Joint Water Resource Board, and the Red River Joint Water Resource District, to analyze historical water-quality trends in three dissolved major ions, three nutrients, and one dissolved trace element for eight stations in the Devils Lake Basin in North Dakota and to develop an efficient sampling design to monitor the future trends. A multiple-regression model was used to detect and remove streamflow-related variability in constituent concentrations. To separate the natural variability in concentration as a result of variability in streamflow from the variability in concentration as a result of other factors, the base-10 logarithm of daily streamflow was divided into four components—a 5-year streamflow anomaly, an annual streamflow anomaly, a seasonal streamflow anomaly, and a daily streamflow anomaly. The constituent concentrations then were adjusted for streamflow-related variability by removing the 5-year, annual, seasonal, and daily variability. Constituents used for the water-quality trend analysis were evaluated for a step trend to examine the effect of Channel A on water quality in the basin and a linear trend to detect gradual changes with time from January 1980 through September 2003. The fitted upward linear trends for dissolved calcium concentrations during 1980-2003 for two stations were significant. The fitted step trends for dissolved sulfate concentrations for three stations were positive and similar in magnitude. Of the three upward trends, one was significant. The fitted step trends for dissolved chloride concentrations were positive but insignificant. The fitted linear trends for the upstream stations were small and insignificant, but three of the downward trends that occurred during 1980-2003 for the remaining stations were significant. The fitted upward linear trends for dissolved nitrite plus nitrate as nitrogen concentrations during 1987‑2003 for two stations were significant. However, concentrations during recent years appear to be lower than those for the 1970s and early 1980s but higher than those for the late 1980s and early 1990s. The fitted downward linear trend for dissolved ammonia concentrations for one station was significant. The fitted linear trends for total phosphorus concentrations for two stations were significant. Upward trends for total phosphorus concentrations occurred from the late 1980s to 2003 for most stations, but a small and insignificant downward trend occurred for one station. Continued monitoring will be needed to determine if the recent trend toward higher dissolved nitrite plus nitrate as nitrogen and total phosphorus concentrations continues in the future. For continued monitoring of water-quality trends in the upper Devils Lake Basin, an efficient sampling design consists of five major-ion, nutrient, and trace-element samples per year at three existing stream stations and at three existing lake stations. This sampling design requires the collection of 15 stream samples and 15 lake samples per year rather than 16 stream samples and 20 lake samples per year as in the 1992-2003 program. Thus, the design would result in a program that is less costly and more efficient than the 1992-2003 program but that still would provide the data needed to monitor water-quality trends in the Devils Lake Basin. |
Abstract
Introduction
Description of Devils Lake Basin
Streamflow and Concentration Data Used for Water-Quality Trend Analysis
Time-Series Model Used for Water-Quality Trend Analysis
Analysis of Streamflow-Related Variability in Concentration Data
Water-Quality Trend Analysis
Dissolved Major Ions
Nutrients
Trace Element
Sampling Design
Summary
References Cited
Appendix
Parametric Flow-Adjustment Model
Survival Regression for Dissolved Nitrite Plus Nitrate as Nitrogen
Variogram Analysis of Flow-Adjusted Concentrations
Model Robustness
1–2. Maps showing:
1. Location of the Devils Lake Basin in North Dakota
2. Locations of stations used for water-quality trend analysis
3–22. Graphs showing:
3. Elevation of Devils Lake, North Dakota, June 30, 1867, through September 30, 2003
4. Daily streamflow for 1960 through September 2003 for the Mauvais Coulee near Cando, North Dakota, and Edmore Coulee near Edmore, North Dakota, stations
5. Calcium concentrations for 1965 through September 2003 for the Lake Irvine near Churchs Ferry, North Dakota, station
6. Streamflow anomalies for the Mauvais Coulee near Cando, North Dakota, and Edmore Coulee near Edmore, North Dakota, stations
7. Measured and fitted dissolved sulfate concentrations for 1970 through September 2003 for the Mauvais Coulee near Cando, North Dakota, station
8. Flow-adjusted dissolved sulfate concentrations for 1970 through September 2003 for the Mauvais Coulee near Cando, North Dakota, station
9. Partial residuals of dissolved sulfate concentrations for the Mauvais Coulee near Cando, North Dakota, station in relation to streamflow anomalies
10. Measured and fitted dissolved ammonia concentrations for 1985 through September 2003 for the Edmore Coulee near Edmore, North Dakota, station
11. Flow-adjusted dissolved ammonia concentrations for 1985 through September 2003 for the Edmore Coulee near Edmore, North Dakota, station.
12. Partial residuals of dissolved ammonia concentrations for the Edmore Coulee near Edmore, North Dakota, station in relation to streamflow anomalies
13. Measured and fitted dissolved nitrite plus nitrate concentrations and censored values for 1980 through September 2003 for the Mauvais Coulee near Cando, North Dakota, station
14. Flow-adjusted dissolved nitrite plus nitrate concentrations and censored values for 1985 through September 2003 for the Mauvais Coulee near Cando, North Dakota, station
15. Measured and flow-adjusted concentrations for 1980 through September 2003 for stations used in water-quality trend analysis
16. Fitted trends for flow-adjusted dissolved calcium concentrations
17. Fitted trends for flow-adjusted dissolved sulfate concentrations
18. Fitted trends for flow-adjusted dissolved chloride concentrations
19. Fitted trends for flow-adjusted dissolved nitrite plus nitrate concentrations
20. Fitted trends for flow-adjusted dissolved ammonia concentrations
21. Fitted trends for flow-adjusted total phosphorus concentrations
22. Fitted trends for flow-adjusted dissolved strontium concentrations
A1. Dissolved nitrite plus nitrate concentrations for the Lake Alice near Churchs Ferry, North Dakota, station
A2. Dissolved nitrite plus nitrate concentrations for the Mauvais Coulee near Cando, North Dakota, station
A3. Dissolved nitrite plus nitrate concentrations and censored values for the Mauvais Coulee near Cando, North Dakota, station
A4. Fourth root of squared residuals for flow-adjusted dissolved sulfate concentrations for the Starkweather Coulee near Webster, North Dakota, station
A5. Fourth root of squared residuals for flow-adjusted dissolved chloride concentrations for the Edmore Coulee near Edmore, North Dakota, station
A6. Estimated variogram for flow-adjusted dissolved sulfate concentrations for the Big Coulee near Churchs Ferry, North Dakota, station for season 1 (March through May)
A7. Estimated variogram for flow-adjusted dissolved sulfate concentrations for the Big Coulee near Churchs Ferry, North Dakota, station for season 2 (June through November)
A8. Estimated variogram for flow-adjusted total phosphorus concentrations for the Channel A near Penn, North Dakota, station for season 1 (March through May)
A9. Estimated variogram for flow-adjusted total phosphorus concentrations for the Channel A near Penn, North Dakota, station for season 2 (June through November)
1. Stations used for water-quality trend analysis
2. Constituents used for water-quality trend analysis
3. Stations and constituents used for water-quality trend analysis and number of samples for concentration data
4. Stations and constituents used to test significance of Channel A step trend and linear trend from 1980 through September 2003
5. Number of samples required to obtain specified error tolerance for estimated median concentrations
A1. Fitted model coefficients for stream stations (sites 1, 2, 4, 7, and 8) and lake stations (sites 3, 5, and 6)
A2. Fitted survival regression model coefficients for dissolved nitrite plus nitrate for stream stations (sites 1, 2, 4, 7, and 8) and lake stations (sites 3, 5, and 6)
A3. Estimated seasonal standard deviations and correlation ranges for flow-adjusted concentrations
A4. Results of test of significance for Channel A step trend and linear trend from 1980 through September 2003 for the Big Coulee near Churchs Ferry, North Dakota, station
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