Darcy Velocity (Spatial Analyst)

Summary

Calculates the groundwater seepage velocity vector (direction and magnitude) for steady flow in an aquifer.

Learn more about how Darcy Flow and Darcy Velocity work

Usage

Syntax

DarcyVelocity (in_head_raster, in_porosity_raster, in_thickness_raster, in_transmissivity_raster, out_magnitude_raster)
ParameterExplanationData Type
in_head_raster

The input raster where each cell value represents the groundwater head elevation at that location.

The head is typically an elevation above some datum, such as mean sea level.

Raster Layer
in_porosity_raster

The input raster where each cell value represents the effective formation porosity at that location.

Raster Layer
in_thickness_raster

The input raster where each cell value represents the saturated thickness at that location.

The value for the thickness is interpreted from geological properties of the aquifer.

Raster Layer
in_transmissivity_raster

The input raster where each cell value represents the formation transmissivity at that location.

The transmissivity of an aquifer is defined as the hydraulic conductivity K times the saturated aquifer thickness b, as units of length squared over time. This property is generally estimated from field experimental data such as pumping tests. Tables 1 and 2 in How Darcy Flow and Darcy Velocity work list ranges of hydraulic conductivities for some generalized geologic materials.

Raster Layer
out_magnitude_raster

The output flow direction raster.

Each cell value represents the direction of the seepage velocity vector (average linear velocity) at the center of the cell, calculated as the average value of the seepage velocity through the four faces of the cell.

It is used with the output magnitude raster to describe the flow vector.

Raster Dataset

Return Value

NameExplanationData Type
out_direction_raster

The output flow direction raster.

Each cell value represents the direction of the seepage velocity vector (average linear velocity) at the center of the cell, calculated as the average value of the seepage velocity through the four faces of the cell.

It is used with the output magnitude raster to describe the flow vector.

Raster

Code Sample

DarcyVelocity example 1 (Python window)

Calculates the groundwater seepage velocity (direction and magnitude) for steady flow in an aquifer.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outDarcyVelocity = DarcyVelocity("gwhead", "gwporo", "gwthick", "gwtrans", 
                            "C:/sapyexamples/output/outdarcymag")
outDarcyVelocity.save("c:/sapyexamples/output/outdarcyvel")
DarcyVelocity example 2 (stand-alone script)

Calculates the groundwater seepage velocity (direction and magnitude) for steady flow in an aquifer.

# Name: DarcyVelocity_Ex_02.py
# Description: Calculates the groundwater seepage velocity 
#              vector (direction and magnitude) for steady 
#              flow in an aquifer.
# Requirements: Spatial Analyst Extension
# Author: ESRI

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inHeadRaster = "gwhead"
inPorosityRaster = "gwporo"
inThicknessRaster = "gwthick"
inTransmissivityRaster = "gwtrans"
outMagnitudeRaster = "C:/sapyexamples/output/outdarcymag"

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Execute DarcyVelocity
outDarcyVelocity = DarcyVelocity(inHeadRaster, inPorosityRaster, inThicknessRaster,
                            inTransmissivityRaster, outMagnitudeRaster)

# Save the output 
outDarcyVelocity.save("C:/sapyexamples/output/outdarcyvel")

Environments

Related Topics

Licensing Information

ArcView: Requires Spatial Analyst
ArcEditor: Requires Spatial Analyst
ArcInfo: Requires Spatial Analyst

6/29/2011