The pilot was practicing low approaches when he experienced a partial loss of engine power during climb out. He continued onto the downwind leg where he applied carburetor heat and determined the loss of power was a result of carburetor ice. The pilot shortened the downwind and base legs, and decided to land on the grass alongside the paved runway. The pilot stated the approach was high and fast, and he was more comfortable landing on the grass as the airplane was equipped with tundra tires. The airplane nosed over during the landing when it contacted standing water on the grass. The right wing of the airplane was substantially damaged. The outside air temperature was reported as 20 degrees Celsius and the was 18 degrees Celsius. A Transport Canada Carburetor Icing Chart indicates the conditions were conducive to serious carburetor icing at descent power.