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Groundwater Numerical Model for 1Dimensional Flow  GN1D
Contents
User Interface
Description of Components
Cross Section
Specifying the topology of the river link via a crosssection is the first step in setting up the GN1D model.
Edit Cross Section  Opens the crosssection editor 
Clear Cross Section  Deletes the crosssection. 
Refer to the Cross Section Editor user guide for details.
Common Controls
These parameters are common with the GAT (Groundwater Analytical Tool) saturated connection model.
Transmissivity  The rate at which groundwater flows horizontally in an aquifer. The transmissivity T for horizontal flow of an aquifer with saturated thickness d and horizontal conductivity K_{sat} is: For an unconfined aquifer, d is the average saturated thickness. 
Specific yield  A ratio indicating the volumetric fraction that an aquifer will yield when all water is allowed to drain out of it under the force of gravity: V_{wd} is the volume of water drained V_{T} is the total volume of the aquifer material 
River to Noflow Boundary  The distance from the left and right hand river banks to the groundwater noflow boundary 
Model Parameters
Additional parameters saturated zone, which are required for the finite difference scheme.
Divisions per Bank  The number of subdivisions per bank. 
Aquifer Floor  The zcoordinate of the aquifer basement (noflow boundary). Uses the coordinate system defined by the cross section. 
Init. Height Method  The method by which the initial groundwater table height is calculated. The two options are:

Infiltration Parameters
Unsaturated zone parameters
Init. Soil Moisture  The initial soil moisture content of the unsaturated zone as volumetric fraction of the total volume. 
Sat. Soil Moisture  The saturated soil moisture content as a volumetric fraction. Field soil moisture is the amount of water that will be retained in the soil if it is allowed to drain under the force of gravity. It can be calculated as: Field Soil Moisture = Sat. Soil Moisture – Specific Yield Field soil moisture is displayed in the user interface but is not editable. 
Field Soil Moisture  Field soil moisture is displayed in the user interface but is not editable. Field soil moisture is the amount of water that will be retained in the soil if it is allowed to drain under the force of gravity. It can be calculated as: Field Soil Moisture = Sat. Soil Moisture – Specific Yield 
Saturated Vertical Hydraulic Conductivity  The saturated vertical hydraulic conductivity. 
Average Suction  The average suction at the wetted front. 
Soil Evaporation Parameters
Parameters for setting the maximum depth at which evapotranspiration can occur.
Extinction Depth  Sets the method by which the evapotranspiration extinction depth will be calculated. The extinction depth is the maximum depth below the ground surface at which evapotranspiration can occur. The two options are:
