Knowledge Bank

Water quality trends from 1977 to 1987 at four stations in the upper Ohio River were explored statistically by use of the seasonal Kendall test for trends and informally described by comparison with flow data and water quality criteria. Monthly data for eight chemical parameters were evaluated: cyanide, phenolics, copper, iron, lead, zinc, dissolved oxygen, and total suspended solids. Results indicated general improvements in the water quality, most notably in decreasing concentrations of cyanide, phenolics, lead, and zinc. The strongest trends were noted for cyanide. Flow adjustment of the data did not affect conclusions about concentration trends, and flow-concentration regressions were weak.