> 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/outflow/wetland-outflow.md).

# Wetland Outflow

The wetland releases water whenever the water volume exceeds the normal storage volume, $$V\_{nor}$$. Wetland outflow is calculated:

&#x20;           $$V\_{flowout}=0$$               if     $$V\<V\_{nor}$$                                                  8:1.2.14

&#x20;           $$V\_{flowout}=\frac{V-V\_{nor}}{10}$$      if      $$V\_{nor} \le V \le V\_{mx}$$                                     8:1.2.15

&#x20;            $$V\_{flowout}=V-V\_{mx}$$ if       $$V>V\_{mx}$$                                                8:1.2.16

where $$V\_{flowout}$$ is the volume of water flowing out of the water body during the day  (m$$^3$$ H$$\_2$$O), $$V$$ is the volume of water stored in the wetland (m$$^3$$ H$$*2$$O), $$V*{mx}$$ is the volume of water held in the wetland when filled to the maximum water level (m$$^3$$ H$$*2$$O), and $$V*{nor}$$ is the volume of water held in the wetland when filled to the normal water level (m$$^3$$ H$$\_2$$O).

Table 8:1-2: SWAT+ input variables that pertain to ponds and wetlands.

|            |                                                                                                                  |      |
| ---------- | ---------------------------------------------------------------------------------------------------------------- | ---- |
| PND\_ESA   | $$SA\_{em}$$: Surface area of the pond when filled to the emergency spillway (ha)                                | .pnd |
| PND\_PSA   | $$SA\_{pr}$$: Surface area of the pond when filled to the principal spillway (ha)                                | .pnd |
| PND\_EVOL  | $$V\_{em}$$: Volume of water held in the pond when filled to the emergency spillway (10$$^4$$ m$$^3$$ H$$\_2$$O) | .pnd |
| PND\_PVOL  | $$V\_{pr}$$: Volume of water held in the pond when filled to the principal spillway(10$$^4$$ m$$^3$$ H$$\_2$$O)  | .pnd |
| WET\_MXSA  | $$SA\_{mx}$$: Surface area of the wetland when filled to the maximum water level (ha)                            | .pnd |
| WET\_NSA   | $$SA\_{nor}$$: Surface area of the wetland when filled to the normal water level (ha)                            | .pnd |
| WET\_MXVOL | $$V\_{mx}$$: Volume of water held in the wetland when filled to the maximum water level (m$$^3$$ H$$\_2$$O)      | .pnd |
| WET\_NVOL  | $$V\_{nor}$$: Volume of water held in the wetland when filled to the normal water level (m$$^3$$ H$$\_2$$O)      | .pnd |
| PND\_FR    | $$fr\_{imp}$$: Fraction of the subbasin area draining into the pond                                              | .pnd |
| WET\_FR    | $$fr\_{imp}$$: Fraction of the subbasin area draining into the wetland                                           | .pnd |
| PND\_K     | $$K\_{sat}$$: Effective saturated hydraulic conductivity of the pond bottom (mm/hr)                              | .pnd |
| WET\_K     | $$K\_{sat}$$: Effective saturated hydraulic conductivity of the wetland bottom (mm/hr)                           | .pnd |
| IFLOD1     | $$mon\_{fld,beg}$$: Beginning month of the flood season                                                          | .pnd |
| IFLOD2     | $$mon\_{fld,end}$$: Ending month of the flood season                                                             | .pnd |
| NDTARG     | $$ND\_{targ}$$: Number of days required for the reservoir to reach target storage                                | .pnd |