Scientific Investigations Report 2005-5224
In cooperation with the Bureau of Reclamation
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The Bureau of Reclamation is considering several alternatives to meet the future municipal, rural, and industrial water-supply needs in the Red River of the North (Red River) Basin, and an environmental impact statement is being prepared to evaluate the potential effects of the various alternatives on the water quality and aquatic health in the basin in relation to the historical variability of streamflow and constituent concentration. Therefore, a water-quality trend analysis was needed to determine the amount of natural water-quality variability that can be expected to occur in the basin, to determine if significant water-quality changes have occurred as a result of human activities, to explore potential causal mechanisms for water-quality changes, and to establish a baseline from which to monitor future water-quality trends. This report presents the results of a study conducted by the U.S. Geological Survey, in cooperation with the Bureau of Reclamation, to analyze historical water-quality trends in two dissolved major ions, dissolved solids, three nutrients, and two dissolved trace metals for nine streamflow-gaging stations in the basin.
Annual variability in streamflow in the Red River Basin was high during the trend-analysis period (1970-2001). The annual variability affects constituent concentrations in individual tributaries to the Red River and, in turn, affects constituent concentrations in the main stem of the Red River because of the relative streamflow contribution from the tributaries to the main stem. Therefore, an annual concentration anomaly, which is an estimate of the interannual variability in concentration that can be attributed to long-term variability in streamflow, was used to analyze annual streamflow-related variability in constituent concentrations. The concentration trend is an estimate of the long-term systematic changes in concentration that are unrelated to seasonal or long-term variability in streamflow. Concentrations that have both the seasonal and annual variability removed are called standardized concentrations. Numerous changes that could not be attributed to natural streamflow-related variability occurred in the standardized concentrations during the trend-analysis period. During various times from the late 1970's to the mid-1990's, significant increases occurred in standardized dissolved sulfate, dissolved chloride, and dissolved- solids concentrations for eight of the nine stations for which water-quality trends were analyzed. Significant increases also occurred from the early 1980's to the mid-1990's for standardized dissolved nitrite plus nitrate concentrations for the main-stem stations. The increasing concentrations for the main-stem stations indicate the upward trends may have been caused by human activities along the main stem of the Red River. Significant trends for standardized total ammonia plus organic nitrogen concentrations occurred for most stations. The fitted trends for standardized total phosphorus concentrations for one tributary station increased from the late 1970's to the early 1980's and decreased from the early 1980's to the mid-1990's. Small but insignificant increases occurred for two main-stem stations. No trends were detected for standardized dissolved iron or dissolved manganese concentrations. However, the combination of extreme high-frequency variability, few data, and the number of censored values may have disguised the streamflow-related variability for iron.
The time-series model used to detect historical concentration trends also was used to evaluate sampling designs to monitor future water-quality trends. Various sampling designs were evaluated with regard to their sensitivity to detect both annual and seasonal trends during three 4-month seasons. A reasonable overall design for detecting trends for all stations and constituents consisted of eight samples per year, with monthly sampling from April to August and bimonthly sampling from October to February.
Abstract
Introduction
Purpose and scope
Streamflow data and hydrologic characteristics
Concentration data used for water-quality trend analysis
Water-quality trend analysis
Time-series model used for water-quality trend analysis
Results of water-quality trend analysis
Major ions and dissolved solids
Nutrients
Trace metals
Possible human causes of historical water-quality trends
Sampling designs to monitor future water-quality trends
Detection of annual trends
Detection of seasonal trends
Summary
References
Appendix 1. Time-series model for streamflow and concentration
Appendix 2. Fitted trends and generalized likelihood ratio test results
Table 2-1. Fitted trends for standardized dissolved sulfate concentrations
Table 2-2. Fitted trends for standardized dissolved chloride concentrations
Table 2-3. Fitted trends for standardized dissolved-solids concentrations
Table 2-4. Fitted trends for standardized dissolved nitrite plus nitrate as nitrogen concentrations
Table 2-5. Fitted trends for standardized total ammonia plus organic nitrogen concentrations
Table 2-6. Fitted trends for standardized total phosphorus concentrations
Figures
Map showing locations of streamflow-gaging stations used for water-quality trend analysis
Graph showing daily mean streamflows (three values per month) and measured total ammonia plus organic nitrogen and total phosphorus concentrations for1970-2001 for the Sheyenne River near Kindred, North Dakota, streamflow-gaging station
Graph showing measured total ammonia plus organic nitrogen and total phosphorus concentrations and fitted annual and seasonal concentration anomalies for 1970-2001 for the Sheyenne River near Kindred, North Dakota, streamflow-gaging station
Graph showing seasonally adjusted total ammonia plus organic nitrogen and total phosphorus concentrations and fitted annual concentration anomalies for 1970-2001 for the Sheyenne River near Kindred, North Dakota, streamflow-gaging station
Graph showing standardized total ammonia plus organic nitrogen and total phosphorus concentrations and fitted trends for 1970-2001 for the Sheyenne River near Kindred, North Dakota, streamflow-gaging station
Graphs showing fitted standard deviation (top graph) and serial correlation at a 10-day time lag (bottom graph) for the high-frequency variability in total phosphorus concentrations for the Sheyenne River near Kindred, North Dakota, streamflow-gaging station
Graph showing fitted annual concentration anomalies for dissolved sulfate for 1970-2001 for main-stem and major tributary stations
Graph showing fitted annual concentration anomalies for dissolved sulfate for 1970-2001 for small tributary stations
Graph showing fitted trends for standardized dissolved sulfate concentrations for 1970-2001 for main-stem and major tributary stations
Graph showing fitted trends for standardized dissolved sulfate concentrations for 1970-2001 for small tributary stations
Graph showing fitted annual concentration anomalies for dissolved chloride for 1970-2001 for main-stem and major tributary stations
Graph showing fitted trends for standardized dissolved chloride concentrations for 1970-2001 for main-stem and major tributary stations
Graph showing fitted trends for standardized dissolved-solids concentrations for 1970-2001 for main-stem and major tributary stations
Graph showing fitted trends for standardized dissolved-solids concentrations for 1970-2001 for small tributary stations
Graph showing fitted annual concentration anomalies for dissolved nitrite plus nitrate as nitrogen for 1975-2001
Graph showing fitted trends for standardized dissolved nitrite plus nitrate as nitrogen concentrations for 1975-2001
Graph showing fitted trends for standardized total ammonia plus organic nitrogen concentrations for 1975-2001
Graph showing fitted annual concentration anomalies for total phosphorus for 1975-2001
Graph showing fitted trends for standardized total phosphorus concentrations for 1975-2001
Graph showing fitted annual concentration anomalies for dissolved manganese for 1970-2001
Graph showing estimated cropland for the Red River of the North at Emerson, Manitoba, Basin for 1974-2001
Graph showing estimated livestock inventory for the Red River of the North at Emerson, Manitoba, Basin for 1974-2001
Graph showing characteristic annual trends for selected sampling designs for dissolved sulfate concentrations for main-stem and major tributary stations
Graph showing characteristic annual trends for selected sampling designs for total ammonia plus organic nitrogen concentrations for main-stem and major tributary stations
Graph showing characteristic seasonal trends for selected sampling designs for dissolved sulfate concentrations for main-stem and major tributary stations
Graph showing characteristic seasonal trends for selected sampling designs for dissolved nitrite plus nitrate as nitrogen concentrations for main-stem and major tributary stations
Graph showing characteristic seasonal trends for selected sampling designs for total ammonia plus organic nitrogen concentrations for main-stem and major tributary stations
Graph showing characteristic seasonal trends for selected sampling designs for total phosphorus concentrations for main-stem and major tributary stations
Tables
Selected characteristics of streamflow-gaging stations used for water-quality trend analysis
Mean daily streamflows for selected stations in the Red River of the North Basin for various periods during 1970-2001
Constituents used for water-quality trend analysis
Stations and constituents used for water-quality trend analysis and number of samples for concentration data
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