Water-Quality Trend Analysis and Sampling Design for the Souris River,Saskatchewan, North Dakota, and Manitoba

摘要

The Souris River Basin is a 24,600-square-mile basin lcoated in southeastSaskatchewan, north-central North Dakota, and southwest Manitoba. This report presents results of a study conducted for the Bilateral Water Quality Monitoring Group by the U.S. Geological Survey, in cooperation with the North Dakota Department of Health, to analyze historic trends in water quality in the Souris River and to determine efficient sampling designs for monitoring future trends. U.S. Geological Survey and Environment Canada water-quality data collected during 1977-96 from four sites near the bounary crossings between Canada and the United States were included in the trend analysis. A parametric time-series model was developed for detecting trends in historic constituent concentration data. The model can be applied to constituents that have at least 90 percent of observations above detection limits of the analyses, which, for the Souris River, includes most major ions and nutrients and many trace elements. The time-series model also was used to determine the sensitivity of various sampling designs for monitoring future water-quality trends in the Souris River.