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Groundwater Numerical Model for 1-Dimensional Flow - GN1D

Owned by rachelb (Deactivated)
18 Jun 2019
3 min read

Contents

User Interface

Description of 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. 

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 Ksat 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: 

 Vwd is the volume of water drained

 VT 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 - The initial groundwater table height is set by the user using the Init. Height field. Note that the groundwater table height is relative to the coordinate system of the cross section.
  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 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:

  1. Calculation Depth - The evapotranspiration extinction depth is calculated from Soil Type and Ground Cover.

  2. Input Depth - The evapotranspiration extinction depth is set by the user via the Depth field.