A type of evaporation pan that is about 1 m (3 ft) square and 0. 5 m (18 in. ) deep. This pan is sunk into the ground to within about 5 cm (2 in. ) of its rim, and the water is maintained at about ground level. It is made of unpainted galvanized iron. The pan coefficient, on an annual basis, is about 0. 8.