Cedar Lake and Half Moon Lake TMDL Implementation Evaluation Monitoring - WCR 4_11


WCR is working in partnership with ACOE ERDC Spring Valley to conduct limnological assessment and research on the two TMDL implentation projects for Cedar Lake St. Croix County and Half Moon Lake City of Eau Claire. Half Moon Lake The Half Moon Lake TMDL set a water quality goal and implemention actions needed to achieve the water quality goal. Implementation actions that have been implemented include MS4 WPDES Stormwater Permit for the City of Eau Claire to address watershed nutrient loading to the lake, relocation of the water ski show team and year one of a three year hericide treatment plan to control curly leaf pondweed. CLP will be treated in 2010 and 2011 and funding is being developed to complete a whole lake alum treatment in 2011. ACOE has primary responsibility for project implementation and WDNR has committed to provided assistance conducting field work and data analysis. Monitoring has been conducted on Half Moon Lake in 2008 and 2009 as part of an effort to examine water quality response to control of curly-leaf pondweed and Eurasian watermilfoil via herbicide treatment and reduction in internal P loading from sediment. Five to six stations are being sampled at 1-m intervals between the lake surface and sediment at biweekly intervals between May and September for in situ temperature, dissolved oxygen, pH, conductivity, light penetration, Secchi transparency, total P, soluble reactive P, and viable chlorophyll. Findings indicated that Secchi transparency was low (~ 1.0 to 1.5 m in 2008 and < 1.0 m in 2009) and that high light attenuation was related to high algal biomass (40 to 50 ug/L in 2008 and 50 to 100 ug/L as chlorophyll in 2009). Chlorophyll concentrations were also positively related to total P concentration, suggesting incorporation of P and conversion to biomass. The trophic state index for chlorophyll ranged between 53 and 77, indicating highly eutrophic conditions. Water quality monitoring is scheduled to continue in 2010 to 2015 or longer. Aquatic plant biomass and population assessments is conducted multiple times per growing seasons. ACOE and WDNR staff conduct pre and post treatment biomass studies, herbicide degredation residual monitoring, and pre and post treatment aquatic plant population assessments. WDNR staff provide up to 20 hrs per week supporting this monitoring and assessment project. Cedar Lake The Cedar Lake TMDL implementation included reducing watershed phosphorus nutrient loading and control of internal loading through seasonal aeration. Monitoring has indicatied that water quality goals have not been achieved. WDNR working in partnership with ACOE ERDC Spring Valley, the Cedar Lake Protection Rehabilitation District, Polk County Land and Water Department, University of Minnesota and the Science Museum of Minnesota will be completing this project over the next 3 years. The objectives of this research are to identify and estimate 1) annual and summer external phosphorus (P) loading, 2) internal P loading from sediments under differing eH and pH conditions and the bioavailable sediment P pool, 3) horizontal water and P exchanges between littoral and pelagic zones, 4) vertical P transport from the hypolimnion to the epilimnion, 5) sedimentation of P, and 6) in-lake water quality trends. These data are being used to construct a P budget for the lake, identify importance P sources and sinks for algal growth, and develop external P loading reduction scenarios that can be used in conjunction with watershed models to manage the lake for improved water quality. The data collection is taking place over a 2 year period starting in 2009. WDNR provides up to 20 hrs per week to complete this monitoring.


These projects are necessary to achieve the water qualtiy goals set forth in the TMDL for both lakes. The results of both studies can be used statewide to set water quality improvement objectives for similiar projects. The Cedar Lake project results are expected to assist in developing water quality improvement actions on approximately 200 other polymictic lakes statewide. The Half Moon Lake results will be critical in developming management recommendations for lakes with expansive curly leaf pondweed populations and complex internal phosphorus loading.


These are milestones that will be reported on in the Division Quarterly Report. Please estimate dates in a manner that encourages success. 1) Each lake has multiple monitoring strategies being employed through out the growing season. Cedar Lake has 9-12 monitoring locations with several sites being instrumented within the lake collecting continuous in lake monitoring, and 2 gage sites for flow and nutrient loading in the watershed. Some sites are monitored continuously, weekly and biweekly. Cedar Lake montioring will be completed in calendar year 2010 with modeling and reporting to be completed by 2013. Half Moon Lake will be monitored for the next several years as herbicide treatments and the alum treatment is completed. Data are entered into the databases as the results are available.

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