A Statistical Evaluation of Trends in the Water Quality of the Niagara River

Using water quality data collected at Niagara-on-the-Lake by the Water Quality Branch, Ontario Region, between 1975 and 1980, pH, alkalinity, total phosphorous, and nitrate concentrations are examined for changes over time. Moving averages, Spearman's rank correlation coefficient and regression methods, which model the seasonal cycle, are used. It appears that pH and alkalinity are decreasing, and nitrate increasing, but these changes do not occur for all months. Since river discharge did not change significantly in any month, the changes in pH, alkalinity, and nitrate are not due simply to changes in discharge. A change in total phosphorous concentrations over years was not detected.