Water Quality Changes Under Ice Cover in Northern Prairie Lakes

Water quality changes under ice cover were studied in seven northern prairie lakes. The lakes are high in dissolved materials and exist essentially as closed systems during the winter months. Ice cover ranging from 53 to 86 cm developed on the lakes. Melted ice samples showed small amounts of dissolved impurities present in surface layers of the ice. No substantial concentrations of any ions were found in the ice of lower layers. Specific conductance increased over 40% under ice cover in two of the lakes studied. Increases in other lakes ranged from 19 to 38%. Major ions showed increases similar to specific conductance in all but one of the lakes. Most dissolved materials returned to their fall levels following the spring ice melt. A concentration phenomenon can be expected to occur in many shallow northern prairie lakes under ice cover. Increases in ion concentration appear related to the extent of ice cover