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<br />Watershed Districts
<br />Watershed Management Organizations (JPB WMO's)
<br />County Local Water Planners
<br />BWSR
<br />November 1, 2005
<br />~~~
<br />Minnesota Lake Water Ouality Assessment Report• Developing Nutrient
<br />Criteria. Third Edation. September 2005.
<br />This attached Minnesota Pollution Control Agency (MPCA) Report serves as the technical basis for
<br />Minnesota's proposed draft lake nutrient criteria. MPCA's previous Lake Water Quality Assessment
<br />(LWQA) reports (1988 and 1990) were developed as a requirement for participation in Clean Lakes
<br />Program (Section 314 of the Clean Water Act of 1987). The first two editions described regional
<br />patterns in lake water quality in Minnesota and served as a basis for developing ecoregion-based
<br />phosphorus criteria. The reports have long provided a basis for assessing the water quality of
<br />Minnesota's lakes and the criteria have been used extensively for water quality goal setting.
<br />As a part of the. Clean Water Action Plan of 1997, nutrients were identified as a significant national
<br />problem and U.S. Environmental Protection Agency was requested to develop a National Nutrient
<br />Strategy. One aspect of this strategy recommended that states develop ecoregion-based criteria for
<br />total phosphorus, total nitrogen, chlorophyll-a, and Secchi transparency.
<br />This edition builds on the previous LWQA reports and provides a detailed description of MPCA's
<br />approach for setting lake nutrient criteria. The draft criteria found in the report were developed based
<br />upon multiple sources of information, including: reference lake data, statewide lake data, historic
<br />reconstruction of lake water quality from fossil algae in lake sediments, lake user perceptions, fishery
<br />and macrophyte requirements and other factors. Draft criteria are presented and examples of how the
<br />criteria maybe used to further lake management are included in this edition. These criteria will be
<br />included in the next revision of the State's water quality standards that is currently underway.
<br />If you have any questions or need a copy of the report, please contact Steven Heiskary,
<br />Environmental Analysis and Outcomes Division, by phone at (651) 296-7217 or (800) 657-3864 or
<br />by e-mail at Steven.heiskary(a)pca.state.mn.us. Copies are also available on-line at:
<br />http://www.pca.state.mn.us/water/lakectuality.html#reports .
<br />cc: BWSR offices
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