Snow and ice depth are measured during the winter months on the eleven primary lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout lakes, unnamed lakes 27-02 [Crystal Bog] and 12-15 [Trout Bog], Fish, Mendota, Monona and Wingra). 10 snow depth measurements are taken in a circle around the sampling location and averaged to single measurement. Sampling Frequency: every 6 weeks during ice-covered season in the north and typically once during the winter in the south. Number of sites: 11.