2005-04-28_AgendaPacket - Laserfiche WebLink

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Tom, by urn r~~~r The Metropolitan Council is charged with developing a comprehensive regional development guide that minimizes the adverse impacts of growth, including adverse impacts on the environment. To help meet this goal, the Minnesota Legislature has mandated the Council to conduct an assessment of the waters (lakes, streams, and rivers) in the TCMA that have been polluted or that have potential for water pollution caused by non-point sources. The monitor- ing data collected by the Council and its partners is used to support regional planning efforts, identify pollution prob- lems, and meet federal and state regulations. A Metropolitan Council survey of Twin Cities residents found that more than three out of four people consider water quality monitoring "very important", making this the high- est-ranking service provided by the Council for two years in a row. Lakes monitored by Council staff and volunteers are typi- cally sampled at two-week intervals from mid-April through mid-October. Most lakes are sampled from one station located at the deepest spot near the center of the lake. Field measurements taken during each monitoring event include temperature, dissolved oxygen, and water clarity (measured as Secchi disk transparency SDT). In addition, a surface water sample is collected for lab analyses that include total phosphorus (TP), total Kjeldahl nitrogen (TKN), and chlorophyll-a (Chl-a). The routine chemical analyses are performed at the Metropolitan Council Environmental Services (MCES) laboratory following U.S. EPA approved methods. A full description of each pro- gram' smethodology can be found at: http://www.metrocouncil.org/environment/ Lakes/index.htm Each lake monitored in 2004 was assigned a water quality grade using an A through F grading system developed by Council staff in 1989. The grading system uses percentile ranges for three water quality indicators, summertime (May-September) average values for total phosphorus, chlorophyll-a, and Secchi depth transparency that were developed from the Council's TCMA lake water quality database. Total phosphorus is a key nutrient measure, ~ .. i ~~ chlorophyll-a is a measure of algae abundance, and Secchi depth transparency is a measure of water clarity. An overall grade is calculated as the average grade for the three individual grades. The grading system allows com- parisons of lake water quality across the TCMA. =--=_ _ In 2004, 35% of the assessed lakes ,= __,- . had overall water quality grades of "A" or "B", meaning that they had relative- ly minor recreational use impairment due to eutrophication. Another 37% of lakes received a water quality grade of "C". However, 28% of lakes received a water quality grade of "D" or "F", meaning that they have poor water quality. There were 119 lakes monitored in both 2003 and 2004. Of these, lake grades were unchanged for 66%, increased for 26%, and decreased for 8%. Analysis of the repeat lakes indicates that the regions' lakes experienced better water quality in 2004 as compared to that of 2003. Furthermore, data from the 2003 lake monitoring program revealed slightly better lake water quality in 2003 as compared to 2002. However, as in past years, analysis revealed no dis- tinct spatial pattern for lake water quality across the region. The Council's lake monitoring programs have played a key role in recent efforts to use satellite images to assess lake water clarity for the region. The use of satellite technology provides acost-effective way to extend the analysis of the region' s lake water quality from just the lakes involved in our ground-based programs to all the lakes in the region. Results of the 2004 satellite assessment of the region revealed similar results to that found through the 2004 ground-based monitoring programs, that the region experi- enced better lake water quality in 2004 than that recorded in 2003. The complete results of the 2004 satellite analy- sis can be found at: http://www.metrocouncil.org/ plan- ning/environmentJTGWaterClarity2004.pdf.