Plate 10 THE SPILLWAY OF A LARGE FARM DAM      Drains of various types are used for the control of water. First, spillways are the largest drains, so that they by-pass the flood overflow from the farm irrigation dams. Plate 10 (upper) is the spillway under construction and (lower) completed. This size spillway is necessary for the "lower valley dam" it serves, which has a catchment area of 350 acres ("Yobarnie" Pond).