Are we seeing progress on reducing phosphorus in Lake Champlain tributaries?
Ann Arbor, MI — Efforts at reducing phosphorus amounts to Lake Champlain have been underway for over 20 years in both the United States and Canada. An analysis of whether phosphorus amounts in tributaries have changed since 1990 is the basis of a study by the U.S. Geological Survey. A new method of evaluating long-term trends in water quality was applied to 20 years of phosphorus and nitrogen data collected in 18 Lake Champlain tributaries by the States of New York, Vermont, and the province of Quebec. The new method filters the raw data to remove year-to-year variation in streamflow. "It is very difficult to detect changes in water quality data because river systems are naturally highly variable from year to year", says USGS scientist Laura Medalie.
Although 20 years of data show no clear patterns or trends, the most recent 10-year period showed improvements in many tributaries for phosphorus and nitrogen (reversing increases seen in the first 10-year period). "Although the magnitude of many of the improvements is small, they should be viewed in the context of a growing population in the Lake Champlain basin," says Medalie. The phosphorus and nitrogen trend results appear to be related to a combination of intensity of agricultural activities, the amount of phosphorus released from wastewater-treatment facilities, and population density. Results are presented for both phosphorus and nitrogen concentrations and yields: concentrations are important for the biological communities and yields are important for determining whether amounts (of phosphorus and nitrogen) are being reduced in the watersheds that drain to the Lake.
The study found that the amount of phosphorus reduction over the last 20 years is about 15% of the reduction target set by a Lake Champlain management plan. "Millions of dollars have been spent on programs to reduce phosphorus inputs to the Lake and people are naturally curious about whether scientific evidence exists to document that the programs are being effective."
Original Publication Information
Results of this study, "Use of flow-normalization to evaluate nutrient concentration and flux changes in Lake Champlain tributaries, 1990-2009," are reported by Laura Medalie, R.M. Hirsch and S.A. Archfield in the special issue on Lake Champlain, of the Journal of Great Lakes Research, published by Elsevier, 2011.
Contacts
For more information about the study, contact Laura Medalie, U.S. Geological Survey, 87 State Street, U.S. Post Office & Fed. Bldg., P.O. Box 628, Montpelier, Vermont 05601; lmedalie@usgs.gov, (802) 828-4512.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
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