AnnAGNPS Pollutant Loading Model
T. Field Pond
The Field Pond routine is designed to accommodate the ponding and release of water & sediment associated with rice and/or crawfish farming as done in the southern US (e.g., Louisiana & Mississippi). A cell may have any combination of a normal landuse and a field pond in a rotation. The key is setting the user-specified rotation for gate openings and closing. On the day in the user-specified rotation when the gate is opened, water & sediment is released according to user-specified quantities. As long as the gate remains open, the area of the field pond is treated identically to the landuse for the remaining area of the cell; i.e., the field pond area is assumed to be zero and the area of the cell is at its maximun. When the gate is closed, the area of the cell is reduced by the area of the field pond and all precipitation in the field pond is trapped within the pond; i.e., the only surface loading contributions come from the non-pond area of the cell.