General Slots
Area
Type: Scalar
Units: Area
Description: The horizontal area of the aquifer.
Information: This value must be greater zero, within the tolerance defined on the Comparison Criteria slot. If the Area is less than the Comparison Criteria, an error is issued at the start of the run.
I/O: Required Input
Links: Not Linkable
Comparison Criteria
Type: Scalar
Units: Fraction
Description: This slot value is used as the tolerance/convergence criteria when comparing scalar slot values, including adjacent conductance values, area and storativity.
Information:
I/O: Required Input, defaults to 0.001 [decimal] = 0.1% if not input.
Links: Not Linkable
Head
Type: Series
Units: Length
Description: This represents the hydraulic or piezometric head, which is a specific measurement of liquid pressure.
Information: This value is presented at the computational timestep.
The convergence on the Head slot is automatically set to None and cannot be changed. Resetting this slot is controlled by the convergence criteria of the Storage slot. That is, if Storage is reset, then Head is reset. If Storage is within convergence and not reset, then Head is also not reset.
I/O: Typically Output, but a specified value (input/rules) is required for initialization as follows. If the run start date falls on the first date of a computational timestep, a value must be provided for the Head at the run initial date. If not, Head Previous must be specified as described below.
Links: Typically not linked.
Head Previous
Type: Series
Units: Length
Description: This slot holds the value of the Head from the previous computational timestep duplicated over the run timesteps, during the computational timestep.
Information: This slot holds values at the run timestep.
The convergence on the Head Previous slot is automatically set to None and cannot be changed. Resetting this slot is controlled by the convergence criteria of the Storage slot. That is, if Storage is reset, then this slot is reset at the next timestep. If Storage is within convergence and not reset, then this slot is also not reset.
I/O: Typically computed, but if the run start date falls after the first date of a computational timestep, a value must be provided for the Head Previous on the start timestep.
Links: Linkable to one or more adjacent objects Head Previous L/R/U/D/A/B
Specified Inflow
Type: Series with Periodic Input
Units: Flow
Description: Inflows to the aquifer typically from other sources that are not modeled. This slot provides a place to specify any inflows that aren’t classified as other inflows, such as recharge.
Information: This value can be positive (into the object) or negative (out of the object). Specified Inflows that are negative can cause the storage to become negative.
I/O: Input as a periodic or series data. Specify a single value if you have a constant value. If no value is specified, it is assumed the value is zero, but that is not shown on the slot.
Links: Not Linkable
Storage
Type: Series
Units: Volume
Description: The volume of water in the aquifer.
Information: This value is computed by the mass balance computation.
I/O: Typically output, but the value on the last timestep of the previous computational timestep must be specified.
Links: Not linkable.
Storativity
Type: Scalar
Units: No Units
Description: The storativity or storage coefficient is the volume of water released/gained from storage per unit decline/increase in hydraulic head in the aquifer, per unit area of the aquifer. Storativity is a unit less quantity, and ranges between 0 and the effective porosity of the aquifer.
Information: This value must be non zero, within the tolerance defined on the Comparison Criteria slot. If the absolute value of the Storativity is less than the Comparison Criteria, an error is issued at the start of the run.
I/O: Required Input
Links: Not Linkable
Revised: 08/02/2021