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GN1D User Interface

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Model Components

Cross Section

Specifying the topology of the river link via a cross-section is the first step in setting up the GN1D model.

Edit Cross Section

Opens the cross-section editor

Clear Cross Section

Deletes the cross-section. 

Common Controls

These parameters are common with the GAT (Analytical Tool) saturated connection model.

Transmissivity

The rate at which groundwater flows horizontally in an aquifer. The transmissivity for horizontal flow  of an aquifer with saturated thickness  and horizontal conductivity  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: 

 is the volume of water drained

 is the total volume of the aquifer material

 

River to No-flow Boundary

The distance from the left and right hand river banks to the groundwater no-flow 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 z-coordinate of the aquifer basement (no-flow 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:

  1. Input
  2. Height at t = 0

 

1.3.1        Option 1: Input

Init. Height

The initial groundwater table height in the coordinate system of the cross section.

 

Option 2: Height at t = 0

The initial groundwater table height is set to the initial river stage.

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 MoistureSpecific 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 MoistureSpecific 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:

  1. Calculation Depth
  2. Input Depth

Option 1: Calculation Depth

The evapotranspiration extinction depth is estimated from soil type and ground cover.

Soil Type

The soil type

Ground Cover

The type of ground cover

Option 2: Input Depth

The evapotranspiration extinction depth is input by the user.

Depth

The maximum depth below the ground surface at which evapotranspiration can occur.

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