Wisconsin Department of Natural Resources
Water Level Fluctuations (WLF) in Wisconsin Impoundments: Evaluation of the Efficacy of WLF in a Partial Drawdown including an Appraisal of Downstream Impacts - NER_01_11 WLF
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The Neshkoro Millpond (WBIC 148500), like most local impoundments, is severally impacted due to excessive sedimentation and over-abundant aquatic plant growth. Recreational use of this system is largely limited to winter recreation due to its eutrophic status. The Neshkoro Millpond is being managed in partnership with Friends of the White River. They received a lake planning grant in 2008 and the findings of the resulting Lake Management Plan advocated conducting a partial drawdown of the lake. It was difficult for the Department to foster adoption of the partial drawdown / water level fluctuation (WLF) action due to the lack of available data concerning partial draw-downs. Additionally, concerns were expressed concerning the potential downstream impacts to the White River from the likely discharge of large volumes of organic sediments through the dam. In attempting to address these concerns it was discovered that little data exists pertaining to the downstream impacts of draw-downs.
The Neshkoro Millpond has applied for and received a Department permit to conduct partial draw-downs (4 vertical feet) of the lake for three consecutive years starting in 2010 and ending in 2013. The draw-down in 2010 will be for a consecutive 12 month period starting in May. Data gathered by this research project will be used to make decisions for the timing of additional draw-downs to take place in 2011 and 2012. Many similar millponds in Marquette and surrounding counties are monitoring the effectiveness of Neshkoro's management efforts to help them determine if a similar action should be taken with their systems. The goals of the Neshkoro Millpond's draw-down are as follows: 1. Improve the recreational and economic value of the millpond through control of EWM, CLP, and coontail and resulting improvement in aquatic plant FQI. 2. Increase mean lake depth and improve sediment quality for native macrophytes via the consolidation, decomposition and subsidence of organic lake bed sediments. The Friends of the White River do not have the monetary resources available to monitor this management effort to determine if their goals are met. This is due to the fact that this group will have to offset hydroelectric generation revenue lost due to this draw-down. The objective of this project is to study the efficacy of the 3-year WLF drawdown on the Neshkoro Millpond along with studying the downstream impacts to the White River. In order for the Department to promote WLF draw-downs as an effective tool it is imperative that the efficacy of draw-downs be quantifiably determined. Information pertaining to the efficacy of draw-downs in this regard is lacking. It is likely that if the Department can demonstrate that draw-downs are an effective management tool it will enable broader acceptance of this WLF tool with local lake managers. Lastly, it is critical to evaluate the seasonality and overall timing of draw-downs to maximize potential benefits. This evaluation project will contribute to the goals of the Water Flux Team. The information gained by this research will used by the team to help establish statewide protocols for draw-down WLF.
Monitoring proposed: Ted Johnson will be the lead on this project and proposes to do the following monitoring activities: Lake Research 1. A full lake PI survey was completed in 2009. A second PI survey will take place in 2012 or 2013 (post draw-down). The costs for this are not included with this project proposal. 2. Six lake bed samples will be taken in May of 2010 to be analyzed for particle size distribution and percent organic matter. 3. Seventy five reference points of lake bed elevations will be taken pre and post draw-down. The local NRCS staff will help me with this and their GPS unit is accurate to 1cm for X, Y and Z coordinates. 4. Aerial coverage of emergent plant communities will be mapped with GPS in 2010 and once again post draw-down (2012 or 2013) 5. A spring electro-fishing survey will be completed by fishery staff in 2010. A full survey is scheduled for 2013 which will provide post draw-down data. The costs for this are not included with this project proposal. Downstream Impact Analysis 1. Two downstream and one upstream stations will be sampled bimonthly for 5-months for the following water quality parameters: a. Ammonia, TP, TSS b. Grab ¿ DO, pH, Temp, Conductivity 2. Quantified Habitat assessed at each of the 3 stations. 3. Insect samples taken for HBI at each of the 3 stations. NOTE: Post draw-down follow up to this sampling is needed and would be proposed under a continuing project proposal. For both lake and stream work the following applies: 1. Number of sample sites, Lake- 75, Stream- 3 2. Number of sampling events, 18 3. Sample collection completed, April, 2011 4. Date all data will be entered into database, June, 2011 5. Date the final report will be complete, August, 2011
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