# Pesticides In Water Bodies

SWAT+ incorporates a simple mass balance developed by Chapra (1997) to model the transformation and transport of pesticides in water bodies. The model assumes a well-mixed layer of water overlying a sediment layer. Figure 8:4-1 illustrates the mechanisms affecting the pesticide mass balance in water bodies.

SWAT+ defines four different types of water bodies: ponds, wetlands, reservoirs and depressional/impounded areas (potholes). Pesticide processes are modeled only in reservoirs.

![Figure 8:4-1: Pesticide mass balance for well-mixed water body with sediment layer (after Chapra, 1997).](/files/y6upMWiWCtIbgU7VeBDG)


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