USGS completes study of phosphorus concentrations in Winooski River

The US Geological Survey (USGS) has completed a study to understand the distribution of phosphorus in the sediments of the Winooski River, a tributary watershed to Lake Champlain, Vermont.

The study, undertaken in collaboration with the University of Vermont and the US Department of Agriculture, Natural Resources Conservation Service in Vermont, will help evaluate the effectiveness of phosphorus-reduction policies implemented by the State.

The Winooski River was selected because it has the largest watershed draining into Lake Champlain, the largest population, and contributes the second largest amount of phosphorus to the Lake.

An estimated four-fold increase in the amount of phosphorus entering Lake Champlain since the early 19th century has resulted in accelerated algal and plant growth in the Lake. Human activities, such as urban and industrial wastewater discharges, and urban and agricultural runoff are responsible for the increase.

The banning of phosphate detergents, controls on agricultural runoff, and the building of phosphorus-removal capabilities at WwTPs following the Clean Water Act of 1972 helped to decrease the amount of phosphorus entering the Lake.

In 1993, however, a Lake Champlain Water-Quality Agreement for higher standards was implemented by the States of Vermont and New York and the province of Quebec, Canada. This agreement required an additional decrease in the amount of phosphorus entering the Lake.

“An understanding of the distribution of phosphorus in river-bottom sediment, and the relation between land use, soil type, slope, and stream flow in a contributing watershed, will help policy and planning efforts determine the best way to reduce the amount of phosphorus entering Lake Champlain,” said Ann Chalmers, the principal USGS hydrologist of the project. “Concentrations of phosphorus in river-bottom sediments were 20 percent higher in urban and agricultural areas than in forested areas. Also, the concentrations of phosphorus in river-bottom sediments increased from the headwaters of the Winooski River Basin to the outlet on the shore of Lake Champlain,” said Chalmers.

River-bottom sediments composed of silt and clay contained 60 percent more phosphorus than sandy bottom deposits. Silt and clay deposits were found in slow-moving or stationary water sites, which are potential sites for the storage of phosphorus.

Copies of the report can be obtained from the USGS at 361 Commerce Way, Pembroke, NH 03275 by calling the Public Information Coordinator at (603) 226-7837. The report is distributed as Fact Sheet 108-98, titled ‘Distribution of Phosphorus in Bed Sediments of the Winooski River Watershed, Vermont, 1997.’

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