# 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).](https://1348478613-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MTFpIHUB1K63DLhLJaf%2Fuploads%2FjeQnOKdwNMz7mA3Nub2O%2FPicture3.png?alt=media\&token=1611d180-7ca2-412f-9c26-68bbf94446c0)