2021 Metro WBIF - Mississippi East Watershed - Rice Creek WD

The purposes of this feasibility study are to 1) better quantify the negative effects of Peltier Lake backflow on water quality in Centerville Lake, 2) improve RCWD?s understanding of the hydraulic relationship between the two lakes, and 3) analyze the technical feasibility, downstream impact, and cost effectiveness of identified disconnection scenarios. Centerville Lake does not meet MN State water quality standards, and suffers from frequent and occasionally intense algae blooms. Monitoring data indicate an increasing trend of phosphorus and chlorophyll-a annual summer means. A significant portion of the annual phosphorus load for Centerville Lake (40-50%, TMDL, 2013) is thought to be from Peltier Lake backflow. Although the TMDL provided an estimate of backflow nutrient loading as a model residual, a more precise understanding is necessary before considering costly management options. Backflow is thought to occur when Peltier Lake?s surface elevation rises above Centerville Lake?s after rain events due to Peltier Lake?s much larger watershed and drawn out time of concentration. If Peltier Lake backflow into Centerville Lake is a problem that requires management (i.e. flow cutoff or reroute), flow rates and elevations are required for project design. Should the lakes be recommended for disconnection, there are two known potential options for maintaining outlet flows from Centerville Lake that, along with any other possible scenarios, need to be analyzed. This is the most important and next achievable step identified for improvement of Centerville Lake in the Peltier Lake and Centerville Lake TMDL Implementation Plan. Understanding, and potentially managing, backflow nutrient loading in Centerville Lake is a pre-requisite to other management actions, such as carp management or sediment-nutrient management.