Reach Evaporation
This method category is used to model evaporation on a reach object.
NoneThis is the default method. No calculations are performed and there are no slots associated with this method. It should be used if you do not want to model evaporation.
Inflow Exponent Pan EvaporationThis method models evaporation based on empirical equations.The equations are as follows:
Note: The exponential calculation is carried out in user units. The value set in the Exponent column of the Evaporation Data slot, as set by the user, must be consistent with the user units for the Inflow slot. Changing the user units on the Inflow slot will produce a different result. There will not be an automatic conversion of the Exponent value.
Slots Specific to This Method
Evaporation Data
Type: Table
Units: FLOW, TIME/LENGTH, NONE, AREA, NONE
Description: This table holds various coefficients and constants for the Inflow Exponent Pan Evaporation method. It holds the following values and units: Threshold Flow (FLOW), Coefficient (TIME/LENGTH), Exponent (NONE), Bankfull Surface Area (AREA), PanEvapCoeff (NONE).
Information: The value in the Exponent column must be consistent with the user units for the Inflow slot. If the user units on the Inflow slot are changed, the Exponent must be changed manually to correspond to the new units. Otherwise different results will be produced.
I/O: Input Only
Links: Not linkable
Evaporation
Type: Series Slot
Units: FLOW
Description: This slot is the output to the Inflow Exponent Pan Evaporation method. It holds the losses as calculated by the empirical equations.
Information:
I/O: Output only
Links: Not linkable
Pan Evaporation
Type: Series
Units: VELOCITY
Description: This slot contains the pan evaporation coefficient
Information: This slot must have a valid value for the Inflow Exponent Pan Evaporation method.
I/O: Input only
Links: Can be linked to data object
Pan EvaporationThis method models evaporation based on the pan evaporation rate, the surface area of the reach and a pan evaporation coefficient.
Slots Specific to This Method
Evaporation
Type: Series Slot
Units: FLOW
Description: This slot is the output to the Pan Evaporation method. It holds the losses as calculated by the equation.
Information:
I/O: Output only
Links: Not linkable
Pan Coefficient
Type: Periodic
Units: NoUnits
Description: This slot holds a coefficient that is applied to the computation.
Information: The coefficient should be greater than 0.0.
I/O: Required input
Links: NA
Inflow Surface Area Table
Type: Table
Units: Flow vs Area
Description: Table relating Inflow to the reach to Surface Area
Information:
I/O: Input Only
Links: NA
Pan Evaporation
Type: Series
Units: Velocity (Length/Time)
Description: This slot contains the pan evaporation rate.
Information: This slot must have a valid input or an error will occur.
Information: Input only
I/O: Can be linked
Surface Area
Type: Series
Units: Area
Description: The water surface area of the reach.
Information: The value in this slot is found by looking up the Inflow on the Inflow Surface Area Table
I/O: Output only
Links: Linkable, possibly to the Wetted Sand Area Excluded slot. See “Wetted Sand Evaporation” for more information.
Method Details
To calculate evaporation, first, the Inflow is looked up on the Inflow Surface Area Table to compute and set the Surface Area. Then, the Pan Coefficient and Pan Evaporation are accessed and verified that there is valid data. Finally, Evaporation is computed as follows:
Revised: 11/11/2019