This editor is displayed when the
button is selected from either the Lateral groundwater flow equation or the Deep groundwater flow equation field in a
subcatchment's properties.
It is used to define either a custom:
- lateral groundwater flow equation - which is used to calculate the groundwater flow between the saturated sub-surface zone of a subcatchment and its associated aquifer node
- deep groundwater flow equation - which is used to calculate the groundwater flow between the saturated sub-surface zone of a subcatchment and its associated aquifer
An example of a lateral groundwater flow equation specified in the editor is shown below.
In this example, a step function is specified to ensure that flow only occurs when the groundwater level is above a threshold of 5.
If no equation is specified in the editor, the standard lateral or deep groundwater flow equation is used by ICM.
The editor consists of the following items:
- A pane in which you can specify a new or edit an existing custom equation.
The following symbols and mathematical functions can be used in a lateral or deep groundwater flow equation:
- Hgw - the height of the groundwater table relative to the aquifer's bottom elevation
- Hsw - the height of the surface water relative to the aquifer's bottom elevation
- Hcb - the height of the channel bottom relative to the aquifer's bottom elevation
- Hgs - the height of the ground surface relative to the aquifer's bottom elevation
- Phi - the porosity of the subsurface soil
- Theta - the moisture content of the upper unsaturated zone
- Ks - the saturated hydraulic conductivity
- K - the hydraulic conductivity at the current moisture content
- Fi - the infiltration rate from the ground surface
- Fu - the percolation rate from the upper unsaturated zone
- A - subcatchment area
- abs(x) - the absolute value of x
- sgn(x) - which is +1 for x >= 0 or -1 otherwise
- step(x) which is 0 for x <= 0 and 1 otherwise
- sqrt(x) - the square root of x
- log(x) - logarithm base e of x
- log10(x) - logarithm base 10 of x
- exp(x) - e raised to the x power
- The standard trig functions (sin, cos, tan, and cot)
- The inverse trig functions (asin, acos, atan, and acot)
- The hyperbolic trig functions (sinh, cosh, tanh, and coth)
- Standard operators, +, -, *, /, ^ (for exponentiation)
- Any level of nested parentheses
- An OK button, which saves any changes and closes the editor.
- A Close button, which discards any changes and closes the editor.