> 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/pesticides-in-water-bodies/pesticide-in-the-water/outflow.md).

# Outflow

Pesticide is removed from the water body in outflow. The amount of dissolved and particulate pesticide removed from the water body in outflow is:

      $$pst\_{sol,o}=Q\*\frac{F\_d\*pst\_{lkwtr}}{V}$$                                                           8:4.1.14

      $$pst\_{sorb,o}=Q\*\frac{F\_p\*pst\_{lkwtr}}{V}$$                                                          8:4.1.15

where $$pst\_{sol,o}$$ is the amount of dissolved pesticide removed via outflow (mg pst), $$pst\_{sorb,o}$$ is the amount of particulate pesticide removed via outflow (mg pst), $$Q$$ is the rate of outflow from the water body (m$$^3$$ H$$*2$$O/day), $$F\_d$$ is the fraction of total pesticide in the dissolved phase, $$F\_p$$ is the fraction of total pesticide in the particulate phase, $$pst*{lkwtr}$$ is the amount of pesticide in the water (mg pst), and $$V$$ is the volume of water in the water body (m$$^3$$ H$$\_2$$O).

Table 8:4-1: SWAT+ input variables that pesticide partitioning.

| Variable Name | Definition                                                                                | Input File |
| ------------- | ----------------------------------------------------------------------------------------- | ---------- |
| LKPST\_KOC    | $$K\_d$$: Pesticide partition coefficient (m$$^3$$/g)                                     | .lwq       |
| LKPST\_REA    | $$k\_{p,aq}$$: Rate constant for degradation or removal of pesticide in the water (1/day) | .lwq       |
| LKPST\_VOL    | $$v\_v$$: Volatilization mass-transfer coefficient (m/day)                                | .lwq       |
| LKPST\_STL    | $$v\_s$$: Pesticide settling velocity (m/day)                                             | .lwq       |