> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-8-water-bodies/impoundment-water-routing/ponds-wetlands.md).

# Ponds/Wetlands

Ponds and wetlands are water bodies located within subbasins that received inflow from a fraction of the subbasin area. The algorithms used to model these two types of water bodies differ only in the options allowed for outflow calculation.

The water balance for a pond or wetland is:

         $$V=V\_{stored}+V\_{flowin}-V\_{flowout}+V\_{pcp}-V\_{evap}-V\_{seep}$$              8:1.2.1

 where $$V$$ is the volume of water in the impoundment at the end of the day (m$$^3$$ H$$*2$$O),$$V*{stored}$$ is the volume of water stored in the water body at the beginning of the day   (m$$^3$$ H$$*2$$O), $$V*{flowin}$$ is the volume of water entering the water body during the day (m$$^3$$ H$$*2$$O), $$V*{flowout}$$ is the volume of water flowing out of the water body during the day (m$$^3$$ H$$*2$$O), $$V*{pcp}$$ is the volume of precipitation falling on the water body during the day (m$$^3$$ H$$*2$$O), $$V*{evap}$$ is the volume of water removed from the water body by evaporation during the day (m$$^3$$ H$$*2$$O), and $$V*{seep}$$ is the volume of water lost from the water body by seepage (m$$^3$$ H$$*2$$O).  $$V*{seep}$$ is added to shallow aquifer storage.