Basic Concepts and Equations
This method can be used with Kinematic Wave, Modified Puls, Muskingum Cunge, and Normal Depth routing methods.
The inundated area is calculated for the current flow rate.
The flow rate is multiplied by the time step and divided by the inundated area to get the depth of water on the inundated area for the time step.
Infiltration from the channel is calculated using the Deficit and Constant Loss Model.
Loss rate is then calculated as the infiltration depth times the inundated area divided by the time step.
|
Q_{loss}=A \cdot{infiltration}/\Delta{t} |
When used with the Normal Depth, Kinematic Wave, and Muskingum-Cunge methods, the wetted perimeter is multiplied by the reach length in order to compute the inundated area.
When used with the Modified Puls method, the optional Elevation-Discharge Function must be specified in the routing parameters. Flow depth is calculated for the current flow from the Elevation-Discharge function. The current storage is divided by the depth to get the inundated area..
Deficit Constant Loss/Gain does not allow for recovery of deficit between events. This method should only be used for single events.
Required Parameters
The initial deficit defines the volume of water that is be required to fill the soil layer at the start of the simulation while the maximum deficit specifies the total amount of water the soil layer can hold.
The maximum deficit is typically defined using the product of the effective soil porosity and an assumed active layer depth, but it should be calibrated using observed data
The percolation rate defines the rate at which water will be infiltrated into the soil layer after the initial deficit has been satisfied in addition to the rate at which percolation occurs once the soil layer is saturated. Typically, this parameter is equated with the saturated hydraulic conductivity of the soil.
The initial deficit must be less than or equal to the maximum deficit. Both parameters are specified as effective depths (e.g., inches or millimeters).
Elevation-Discharge function for Modified Puls routing.
