> 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/sediment-in-water-bodies/mass-balance.md).

# Mass Balance

The mass balance equation for sediment in a water body is:

      $$sed\_{wb}=sed\_{wb,i}+sed\_{flowin}-sed\_{stl}-sed\_{flowout}$$                          8:2.1.1

where $$sed\_{wb}$$ is the amount of sediment in the water body at the end of the day (metric tons), $$sed\_{wb,i}$$ is the amount of sediment in the water body at the beginning of the day (metric tons), $$sed\_{flowin}$$ is the amount of sediment added to the water body with inflow (metric tons), $$sed\_{stl}$$ is the amount of sediment removed from the water by settling (metric tons), $$sed\_{flowout}$$ is the amount of sediment transported out of the water body with outflow (metric tons).