MMINNEAPOLISINNEAPOLIS PPARKARK && RRECREATIONECREATION BBOARDOARD 20122012 WWATERATER RRESOURCESESOURCES RREPORTEPORT Environmental Stewardship Water Resources Management www.minneapolisparks.org January 2015 2012 WATER RESOURCES REPORT Prepared by: Minneapolis Park & Recreation Board Environmental Stewardship 3800 Bryant Avenue South Minneapolis, MN 55409-1029 612.230.6400 www.minneapolisparks.org January 2015 Funding provided by: Minneapolis Park & Recreation Board City of Minneapolis Public Works Copyright © 2015 by the Minneapolis Park & Recreation Board Material may be quoted with attribution. TABLE OF CONTENTS Page Abbreviations ............................................................................................................................. i Executive Summary ............................................................................................................... iv 1. Monitoring Program Overview .............................................................................................. 1-1 2. Birch Pond .............................................................................................................................. 2-1 3. Brownie Lake ......................................................................................................................... 3-1 4. Lake Calhoun ......................................................................................................................... 4-1 5. Cedar Lake ............................................................................................................................. 5-1 6. Diamond Lake ........................................................................................................................ 6-1 7. Grass Lake .............................................................................................................................. 7-1 8. Lake Harriet ............................................................................................................................ 8-1 9. Lake Hiawatha ........................................................................................................................ 9-1 10. Lake of the Isles ................................................................................................................... 10-1 11. Loring Pond .......................................................................................................................... 11-1 12. Lake Nokomis ...................................................................................................................... 12-1 13. Powderhorn Lake ................................................................................................................. 13-1 14. Ryan Lake ............................................................................................................................ 14-1 15. Spring Lake .......................................................................................................................... 15-1 16. Webber Pond ........................................................................................................................ 16-1 17. Wirth Lake ............................................................................................................................ 17-1 18. Comparisons Among Lakes ................................................................................................. 18-1 19. Public Beach Monitoring ...................................................................................................... 19-1 20. Exotic Aquatic Plant Management ....................................................................................... 20-1 21. Wetland Health Evaluation Program (WHEP) ..................................................................... 21-1 22. Bassett Creek Watershed Outlet Monitoring Program (WOMP) Station ............................. 22-1 23. Minnehaha Creek Watershed Outlet Monitoring Program (WOMP) Station ...................... 23-1 24. National Pollutant Discharge Elimination System (NPDES) Monitoring ............................ 24-1 th st 25. Nokomis 56 & 21 (BMP) Monitoring .............................................................................. 25-1 26. Xerxes Avenue at Minnehaha Creek Monitoring Station…………………………………26-1 27. Golf Course Wetland Monitoring ......................................................................................... 27-1 28. Climatological Summary ...................................................................................................... 28-1 29. Water Quality Education ...................................................................................................... 29-1 30. Quality Assurance Assessment Report ................................................................................. 30-1 31. Additional Sources of Water Quality Information ............................................................... 31-1 32. References ............................................................................................................................ 32-1 Appendix A – Box and Whisker Plot Record ....................................................................... A-1 Appendix B – Brownie, Powderhorn and Wirth Lake Macrophyte Maps ........................... B-1 Appendix C – Lake Monitoring Data 2012 .......................................................................... C-1 2012 Water Resources Report – Minneapolis Park & Recreation Board EXECUTIVE SUMMARY As part of its stewardship of the lakes and other water bodies within the City of Minneapolis, the Minneapolis Park and Recreation Board (MPRB) monitors lakes, streams, and stormwater flows for contaminants and other water quality indicators. This report presents the results for the 2012 monitoring season. The report is primarily based on data collected by the MPRB Environmental Operations Section. The MPRB monitors the water quality of Brownie, Calhoun, Cedar, Diamond, Grass, Harriet, Hiawatha, Isles, Loring, Nokomis, Powderhorn, Spring, Webber, and Wirth Lakes. Data from 2003- 2012 are used to calculate trophic state index (TSI) trends and estimate the trophic status for each lake. Based on the trophic state report for 2012 the following observations are made: Lakes with increasing Lakes with decreasing Lakes with stable trend water quality indicators water quality indicators Diamond Lake Brownie Lake Lake Calhoun Grass Lake Cedar Lake Lake Harriet Webber Pond Lake of the Isles Wirth Lake Loring Pond Lake Nokomis Powderhorn Lake Spring Lake Water Quality Highlights The Minneapolis lakes experienced both a very wet spring and also drought conditions from August through October during the 2012 sampling season. The water quality of Lakes Calhoun and Harriet continues to be strong for lakes in urban settings; however, the last decade of monitoring data has begun to trend towards slight degradation in water quality. Monitoring data should be used to track this nascent trend and to develop next generation plans for these lakes. Powderhorn Lake received its ninth barley straw treatment. Duckweed and filamentous algae impacted the aesthetics and clarity at Powderhorn Lake in 2012. An aquatic plant survey found that C. demersum (coontail) a native plant has begun to colonize the lake, bringing the total number of submerged aquatic plants in the lake to three up from zero. Wirth Lake continued its increasing water quality trend. Wirth Lake currently meets the Minnesota Pollution Control Agency (MPCA) guidelines for phosphorus, chlorophyll-a, and secchi depth and has for most years since 2000. Lake of the Isles and Cedar Lake both exhibit stable TSI values. These lakes have received significant improvements in stormwater treatment since the 1990’s. They exhibited a resulting improvement in water quality and have stabilized over the last five years at a higher level of water quality. 2012 Water Resources Report – Minneapolis Park & Recreation Board Page iv Qualitative monitoring of the floating artificial islands in Spring Lake showed establishment of planted vegetation. Weedy and invasive plants have also self-seeded to the islands. MPRB will monitor water quality parameters in the lake as well as the success of vegetation on the islands. The project will allow MPRB to evaluate artificial islands as a management technique for aquatic and wetland systems. The water quality at Lake Hiawatha is largely controlled by the inflow from Minnehaha Creek. Drought years strongly influence this lake. Monitoring data from Lake Hiawatha as well as flow data from the Minnehaha Creek WOMP station and the Minneapolis Park Board Xerxes station were used in the Minnehaha Creek – Lake Hiawatha TMDL study. Because of the long-term datasets collected by MPRB, the TMDL study will be based on actual watershed and in-lake conditions rather than relying on modeled data. The MPRB monitored 12 public beaches for Escherichia coli (E. coli, as recommended by the US Environmental Protection Agency). These bacteria are used as proxy indicators of pathogens in water. Four beaches had extremely low season long geometric means where the geometric mean was below 10. The single sample limit of 1,260 E. coli per 100 mL of water was exceeded at Harriet Southeast Beach and Wirth Beach during the 2012 beach season. Eurasian water milfoil harvesting was carried out on Calhoun, Cedar, Harriet, Lake of the Isles, Lake Nokomis and Wirth Lake in 2012. Plant growth in the permitted harvest areas were very low compared