# Outflow

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

           $$pst\_{sol,o}=Q\*\frac{F\_d\*pst\_{rchwtr}}{V}$$                                                                      7:4.1.13

           $$pst\_{sorb,o}=Q\*\frac{F\_p\*pst\_{rchwtr}}{V}$$                                                                    7:4.1.14

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 reach segment (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, $$pst*{rchwtr}$$ is the amount of pesticide in the water (mg pst), and $$V$$ is the volume of water in the reach segment (m$$^3$$ H$$\_2$$O).

Table 7:4-1: SWAT+ input variables that pesticide partitioning.

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


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