Utilizing Geographic Information Science Advancements For Bathymetric Mapping and Dredging Assessment of a Small Urban Lake in Southeastern Minnesota

Currently emphasis on accurate and timely collection of fisheries data generates a need for investigation into advanced techniques in bathymetry, including recent refinements in Geographical Information Science (GIS) and Global Positioning Systems (GPS). The study area for this project was the east basin of Lake Winona, a small Mississippi River floodplain lake in Winona, Minnesota USA. Lake Winona was the site of recent dredging operations aimed at decreasing littoral zone areas to reduce plant growth and stunted fish populations. To assess potential effectiveness of dredging operations, bathymetric data were collected with a Garmin depthfinder and GPS unit, and interpolation techniques to produce lake morphometric characteristics (splining, kriging, and inverse distance weighting) were compared within ESRI’s ArcMap 9.0. All interpolation methods produced similar outputs for cross validation statistical comparisons, although kriging produced the best predictive output of actual bathymetric contouring for Lake Winona. Calculation of morphometric characteristics from derived bathymetric information showed significant changes in Lake Winona compared to historic accounts. Lake dredging was successful in reducing littoral zone areas by 30 percent and increasing lake volume by 28 percent, while increasing the mean depth by 60 percent (from 2.6 feet to 4.3 feet). Habitat for stunted fish populations was substantially reduced. Today, information from this project is being used to assess the feasibility of further bathymetric studies and to refine management approaches to improve the Lake Winona fishery.