Frazil and anchor ice

Frazil ice is formed in turbulent streams when temperatures are below freezing.. Needles of ice from on the surface and are submerged by the turbulent water forming a turbid mass of ice and water. Slush ice is caused by heavy snowfall on open water that is near or below freezing point. Slush ice chokes intakes, penstocks and turbines, necessitating the closing of power facilities to clear the pipes. Experiments with steam to combat ice at intakes have proven expensive and inefficient. Compressed air forced through the water at the intakes has been effective. Anchor ice forms most rapidly on dark colored streambeds of turbulent streams on cold clear nights. Anchor ice never forms under the cover of sheet ice. Anchor ice will thaw loose and float away during days of bright sunshine and form again on very cold clear nights.Discussion by Ralph L. Parshall.