.. _transport:
.. role:: raw-html(raw)
:format: html
4-Transport
===========
After generating particle paths and estimating ammonium, nitrate, and
phosphate concentrations at the water table, the Transport Module
(Figure 4-1) estimates the plumes of ammonium, nitrate, and phosphate,
i.e., the spatial distribution of their concentrations, using the
Domenico solution’s steady state, 2D version. Note that the calculations
performed by this module are the most computationally demanding out of
all the modules. If there is insufficient memory or free disk space,
calculations may fail unexpectedly. If this happens, users need to
reduce the resolution or conduct the simulation for a sub-area of the
domain. A common practice is to first split the OSTDS into several
sub-areas, prepare corresponding OSTDS input files, and then run
ArcNLET-Py for the input files. There is no need to re-do the flow
and Particle Tracking Modules because the flow conditions do not
change between the ArcNLET-Py runs. After the ArcNLET-Py runs, one
can mosaic together the plumes generated by the runs.
The transport model is based on an analytical solution introduced by
Domenico and Robbins (1985) for the advection-dispersion equations that
govern the transport of ammonium, nitrate, and phosphate. This analytical
solution considers advection along a single dimension and dispersion
along one, two, or three dimensions. Additionally, it assumes homogenous
flow fields and homogeneous aquifer transport properties. The advantage
of using an analytical solution is that the concentration of contaminants
can be determined anywhere, anytime, without having to solve any
differential equations numerically. For more advanced solute transport
modeling with complicated hydrogeological conditions (e.g., heterogeneous
aquifer transport properties), one should use more sophisticated
software and/or computer codes such as MT3DMS.
The Domenico solution used in this Python Toolbox is a two-dimensional,
steady-state with first-order decay (first-order decay is used to simulate
denitrification (Domenico, 1987)). This formulation produces a two-dimensional
plume later converted to a pseudo-3D form by extending the 2D solution in
the vertical dimension. Using a pseudo-3D form avoids the large memory
requirements of calculating the complete 3D solution formulated by
Domenico and Robbins (1985). The shape of each plume depends on the groundwater
flow field near the NO\ :sub:`3`, NH\ :sub:`4`, or PO\ :sub:`4` source, as
determined by the Groundwater Flow Module. Since the analytical solution
requires uniform flow to deal with heterogeneity in the flow magnitude,
the harmonic mean averaged along the flow path is used. This average value
is used in evaluating the analytical solution. Heterogeneous porosity is
handled by averaging the porosity along the path using the arithmetic mean.
Heterogeneous decay coefficients and dispersivities are handled using a
constant value for each plume, with the possibility of the values varying
from plume to plume. The values of the decay coefficient and dispersivities
should be representative of the plume. Each plume is individually warped to
conform to a flow path, using a first- or second-order transformation or
a thin-plate spline transformation to handle curved paths.
For phosphate transport, the module supports both linear and Langmuir
adsorption models to account for sorption processes. The
**linear distribution coefficient** (\(K_d\)) is used for the linear isotherm,
representing a constant ratio between the adsorbed and dissolved phosphate
concentrations. The **Langmuir adsorption model** includes the Langmuir
coefficient and the maximum sorption capacity, which describe the affinity
of phosphate for adsorption sites and the maximum amount of phosphate that
can be adsorbed onto the soil surface, respectively. These models allow for
a more accurate representation of phosphate transport, considering both
reversible adsorption processes and surface saturation effects.
Note that the Domenico solution is for a single species
(i.e., ammonium, nitrate, or phosphate). Zhu et al. (2016) expanded the solution
for both ammonium and nitrate with the transformation introduced by
Sun et al. (1999). The current version of ArcNLET-Py is based on the work of
Zhu et al. (2016).
The outputs of the Transport Module are a raster, representing the combined
concentration distribution of all OSTDS, and an auxiliary point shapefile that
stores associated plume information (e.g., transport simulation parameters,
calculated mass inputs, etc.) for each OSTDS. Lastly, the plume info shapefile
output from the Transport Module is used in the functionality of the
Load Estimation Module to determine load from OSTDS to surficial water bodies.
.. figure:: ./media/transportMedia/media/image1.png
:align: center
:alt: A screenshot of a computer Description automatically generated
Figure 4-1: The Transport Module.
.. warning::
When running the ArcNLET-Py transport module, be cautious about processing too many features at once, especially when dealing with a large number of septic tanks (OSTDS). It has been observed that attempting to run calculations on more than 1,000 OSTDS at a time can cause the system to become unstable or fail due to the high demand on system resources. This issue is related to ArcGIS Pro's heavy use of storage and memory, particularly for storing intermediate raster files.
For best results, it is recommended to split large datasets into smaller subsets and run the transport module on these smaller groups separately. This approach helps manage resource usage and reduces the likelihood of system crashes or storage issues. Keep in mind that temporary files may not always be automatically deleted by ArcGIS Pro, which could further impact available disk space.
Input Layers
------------
- **Types of Contaminants:** This option allows users to select the type
of contaminants to be modeled in the transport simulation. The three
available options are as follows.
a. **Nitrogen:** This selection enables the modeling of nitrogen species,
specifically ammonium (NH\ :sub:`4`\ :sup:`+`) and nitrate
(NO\ :sub:`3`\ :sup:`-`). When this option is selected, input fields
related to nitrogen transformation processes, such as nitrification
and denitrification, become available.
b. **Phosphorus:** This selection focuses on the transport of phosphorus in
the form of phosphate (PO\ :sub:`4`\ :sup:`3-`). Input fields related to
phosphorus adsorption processes, including options for linear and Langmuir
sorption isotherms, are revealed to provide detailed modeling of phosphorus
behavior in the subsurface.
c. **Nitrogen and Phosphorus:** This option enables the simultaneous modeling
of both nitrogen (ammonium and nitrate) and phosphorus (phosphate) species.
It activates input fields for nitrogen transformation processes and
phosphorus adsorption, allowing for a comprehensive assessment of nutrient
transport and interaction within the study area.
- :raw-html:`Consideration of NH4-N:` This option allows for estimating the
load of ammonium (NH\ :sub:`4`\ :sup:`+`) to surface water bodies. By
default, this option is unchecked. Utilizing this option increases
computation time. There are several input fields revealed when
considering NH\ :sub:`4`\ :sup:`+`.
- **Input Source locations (point):** This layer specifies the areas of
the contaminant sources. This point feature class may optionally
contain several numeric (FLOAT) fields in its attribute table that
allow for the specification of transport parameters on a
source-by-source basis. The fields that are permitted are described
in Table 4‑1.
- **Input Water bodies (polygon):** Specifies the locations of water
bodies. It is the same input used in the Particle Tracking
Module.
- **Input Particle Paths (polyline):** The particle paths
correspond with the **Source locations** and are the output file of the
Particle Tracking Module. The Transport Module uses this file to
calculate the average velocity (harmonic mean) and porosity (arithmetic
mean) along each flow path. These values are then used for the
calculation of each plume.
.. raw:: html
Table 4‑1: Optional parameters in the attribute table of the source locations file.
+--------------+-----------------------------------+-------------------+
| **Field | **Description** | **Corresponding |
| Name** | | Parameter** |
+==============+===================================+===================+
| C_NH4-N | The initial concentration of the | C0 |
| | source plane for | [L] |
| | ammonium-nitrogen. | |
+--------------+-----------------------------------+-------------------+
| C_NO3-N | The initial concentration of the | C0 |
| | source plane for | [L] |
| | nitrate-nitrogen. | |
+--------------+-----------------------------------+-------------------+
| C_PO4-P | The initial concentration of the | C0 |
| | source plane for | [L] |
| | phosphate-phosphorus. | |
+--------------+-----------------------------------+-------------------+
The field names must be labeled as shown in the table and be of the
FLOAT type. If one wants to use constant concentrations of ammonium,
nitrate, and/or phosphate for all OSTDS, he/she can input the concentration
values in the **Parameters** section.
Options and Parameters
----------------------
- **Solution type:** The form of the Domenico solution to use. The
available options are:
a. **DomenicoRobbinsSS2D:** The two-dimensional, steady-state Domenico
solution without decay (i.e., denitrification). This is a legacy method,
and it is retained for understanding the impact of denitrification. This
solution should not be used for OSTDS modeling because denitrification
is always expected to occur.
b. **DomenicoRobbinsSSDecay2D:** The two-dimensional, steady-state
Domenico solution with decay. This solution should always be used.
- **Plume warping control point spacing [Cells]:** This parameter is used
to warp the plume to specific flow paths. It specifies the number of
cells along the plume centerline (starting from the OSTDS location)
separating the control points for warping. The control point spacing,
plume length, and the plume cell size determine the number of control
points. TakingFigure 4-1 as an example, the parameter value of 48
means that a control point is set for every 48 cells along the plume
centerline. The warping **Method** includes three options: spline,
first-order polynomial (also called affine transformation), and
second-order polynomial. The default method is the second-order
polynomial transformation.
a. A smaller **Plume warping control point spacing** yields a more
accurate warp at the expense of a longer computation time. The
computation time depends on the **Method** used for warping.
Setting the **Plume warping control point spacing** too small may
increase computation time or cause the warp to fail if the flow
path is nearly straight. Setting this value too large is not
problematic since the software automatically ensures sufficient
control points are available for warping. If the algorithm cannot
generate a sufficient number of points (likely because the plume
is too short or has a cell size that is too large), then the warp
fails. The default value (48 cells) should be acceptable for most
applications. For example, if the spacing is set to 48 cells,
control points are spaced 48 raster cells apart. If it is
impossible to place the required number of control points (i.e.,
due to a short plume), the program adjusts this number to an
appropriate value. If, after adjusting spacing, the requirements
for the number of points cannot be met, the warp fails, and the
plume is discarded. If many plumes are discarded for this reason,
a possible solution is to increase the plume resolution (i.e.,
decrease the **Plume Cell Size** value).
- **Plume warping methods:** The warping algorithm to use. More details
of the wrapping methods can be found on the Esri website at
https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/warp.htm.
ArcNLET-Py has the following three options:
a. **Spline:** This option is for the thin-plate spline
transformation. This method has the best overall result regarding
computational time and numerical accuracy.
b. **Polynomial2:** This selection is for the second-order polynomial
transformation. This transformation can be used in exceptional
cases where the flow paths are simple and are generally
arc-shaped. This transformation is the default, as it yields
slightly more accurate results than the Spline method does.
c. **Polynomial1**: This selection is for the first-order polynomial
(affine) transformation. This transformation should only be used
for troubleshooting or when the flow path is straight.
- :raw-html:`Threshold Concentration [M/L3]:` By default, the threshold value
is set to 10-6 for ammonium and nitrate concentrations. If a
concentration in a cell is smaller than the threshold value, it is
not used for the plume calculation. This value can speed up
computation and reduce memory requirements by discarding portions of
the plume below the threshold value. Setting this value too low may
increase resource utilization beyond the capabilities of the machine
running the model. Setting this value too high may result in
discarding significant portions of the plume, resulting in large mass
balance errors. The units of the threshold value are the same as
those of NH4_conc and NO3_conc. For example, if the units of NO3_conc
are in mg/L, then the default of 1E-6 mg/l should be sufficient for
most applications. If the concentration units are not in mg/L, this
value should be changed to the equivalent value in the correct units.
- **Post-processing**: This setting controls how plumes intersecting
water bodies are handled:
a. **None:** When the plumes reach a water body, the plume terminates
with a straight line perpendicular to the flow direction. This
option is for troubleshooting or when the other methods are too
slow.
b. **Medium:** Plumes are all post-processed as a single raster.
Plumes that reach a water body are terminated with a shape that
conforms to the shape of the water body boundary. This option
works in cases where the configuration of the water bodies is
simple (e.g., a single large water body). This setting is the
default selection.
c. **Full:** Plumes are processed individually. This option is the
slowest of the three and, depending on the number of plumes, is
significantly slower than the **Medium** option. **Medium** and
**Full** produce the same result when only a single plume exists.
In cases where plumes appear to cross small creeks, ditches, or
other complicated water body configurations, this option or the
**None** option should be used.
- **Domenico Boundary:** A mass balance calculation requiring either
specifying or estimating the inflow mass rate from an OSTDS. When the
inflow mass rate is specified, ArcNLET-Py needs to estimate the
height (called Z) of a source plane associated with an OSTDS. If the
Z value is specified, ArcNLET estimates the inflow mass rate.
Although a 2D version of the Domenico solution is used, the Z value
is required since it converts the 2D solution into a pseudo-3D form
by extending the 2D solution vertically downwards. There are two
options for this variable:
a. **Specified Input Mass Rate:** Setting the **Domenico Boundary**
to this option enables the **Mass input [M/T]**. The value of the
**Mass input** (**M\ in)** parameter represents a known input mass
rate, in units of mass per time, from the constant concentration
source plane. The mass unit must be the same as that of :raw-html:`NO3-N Concentration` (C0), and/or the :raw-html:`PO4 Concentration` (C0),
The time units must be the same as the time units of the groundwater
flow velocity magnitude. A 20,000 mg/day value per OSTDS is a
reasonable starting point. Using a specified mass inflow rate
requires estimating the Z value, and the option for a
**Maximum Z [L]** value, which limits the value of Z, is enabled.
In extreme situations, an unreasonably large Z value may be estimated
based on the specified input mass rate. The **Z max [L]** value
is the maximum Z value of the Domenico source plane that limits
the value of Z, and the default is 3 meters. Note that the value
for **Source Dimension Z [L]** is automatically estimated when using
the **Specified Input Mass Rate** option.
b. **Specified Z:** Setting the **Domenico Boundary** parameter to
this option enables the **Source Dimension Z [L]** allocation. The
mass units of **M\ in** are automatically calculated. The Z value
is based on the measured plume’s thickness.
- **Source Plane Parameters:** The user can determine which option to use
based on available information. For example, if only the inflow mass
rate is available from a report, the first option should be used. If a
reasonable Z value is available, the second option should be used.
- **Source Dimension Y (m)** and **Source Dimension Z (m):** The
dimensions are in map units and should be the same as the DEM unit.
The source plane represents the **Source Dimension Y [L]** (Y)
and **Source Dimension Z [L]** (Z). The Y\ **-**\ value is estimated
by measuring the width of the drainfield in the direction
perpendicular to groundwater flow. The default values are
**Source Dimension Y [L]** is 6 meters, and **Source Dimension Z**
is 1.5 meters. The value of Z should not typically exceed 3 meters.
These values are in units of meters and should be changed if the
map units are not meters. The units of Y and Z must have the same
units for length as the groundwater flow velocity magnitude.
If the **Domenico Boundary** parameter is set to **Specified Input Mass Rate**,
the **Source Dimension Z** value is calculated automatically.
If the **Domenico Boundary** parameter is set to **Specified Z**,
then the **Mass Input** value is calculated automatically.
- **Plume cell size [L]**: The grid resolution in map units over which
the Domenico solution is evaluated. Smaller values yield
higher-resolution plumes at the expense of increased computation time
and memory usage. An out-of-memory or other error likely occurs if
the cell size is too small when there are many plumes. The cell size
should be between 5 and 30 times smaller than the source width to
represent the plume. By default, the cell size is set to a value 15
times smaller than the value of **Source Dimension Y**. This value
can be set higher to speed up calculations. The plume resolution can
differ from the DEM and generally should be smaller. Likewise, the
resolution of the plumes should be smaller than the resolution used
in particle tracking, rendering the model execution more flexible.
The units of this parameter must have the same length units as the
groundwater flow velocity magnitude. Although a general guideline is
provided for reasonable values of this parameter, the smaller the
**Plume cell size**, the more accurate the solution.
- **Volume Conversion Factor:** This factor converts volumes calculated
from the units of length to the volume units used for concentration.
For example, if the value of NO3_conc was specified using the unit of
mg/L, and the length units (units of the cell size, source
dimensions, dispersivities, and length portion of the groundwater
flow velocity magnitude units) are in meters, the conversion factor
is 1,000 since 1,000 liters equals one cubic meter. The correct
conversion factor is CRITICAL to calculate the nitrate load
correctly.
- :raw-html:`Bulk Density [M/L3]:` The bulk density of the soil. By default,
this value is 1.42 g/cm\ :sup:`3`.
- **Nitrogen Parameters:**
a. :raw-html:`NO3-N Concentration [M/L3]:` The concentration of the source
plane. Its range is between 0 and 80 mg/L, and the default is 40
units (e.g., mg/L). If there are data in the :raw-html:`Input Source locations
(point)` (i.e., the exported shapefile from VZMOD) in the No3_conc
field, then the :raw-html:`NO3-N Concentrations [M/L3]` input field is
removed from the Geoprocessing Pane, and the values in the :raw-html:`Input
Source locations (point)` attribute table are used.
b. :raw-html:`NH4-N Concentration [M/L3]:` The NH:raw-html:`4` concentration
of the source plane. If the input source locations (shapefile)
contain a column named nh4_conc, then the value in the input file
is used. This field allows users to enter different initial
concentrations for different OSTDS. If not, the input value here
is the initial value for all OSTDS. By default, the value is 10
mg/L. If there are data in the :raw-html:`Input Source locations (point)`
(i.e., the exported shapefile from VZMOD) in the nh4_conc field,
then the :raw-html:`NH4-N Concentrations [M/L3]` input field is removed
from the Geoprocessing Pane, and the values in the :raw-html:`Input Source
locations (point)` attribute table are used.
- **Dispersivities:** These approximate values for a given soil type's
horizontal and longitudinal dispersivities may be obtained from the
literature (e.g., Freeze and Cherry, 1979). The defaults are based on
a model by USGS scientists of the Naval Air Station in Jacksonville.
This number should be changed accordingly if the map units are not
meters. This parameter has two settings:
a. :raw-html:`NO3 Dispersivity αL [L]:` This is for the longitudinal
dispersivity of :raw-html:`NO3`. The default is 2.113 m/day.
b. :raw-html:`NO3 Dispersivity αTH [L]:` This parameter represents the
horizontal dispersivity of :raw-html:`NO3`. The default value is
0.234 meters.
c. :raw-html:`NH4-N Dispersivity αL [L]:` This is the longitudinal
dispersivity for :raw-html:`NH4+`. By default, the value is
2.113 meters.
d. :raw-html:`NH4-N Dispersivity αTH [L]:` This is the horizontal
transverse dispersivity of :raw-html:`NH4+`. By default, the
value is set to 0.234 meters.
e. :raw-html:`kd for NH4-N cm3/g:` AKA the
:raw-html:`Adsorption coefficient [L3/M]:` The measure of how much
:raw-html:`NH4+` is adsorbed by the soil at a given temperature
and pH. By default, this value is set to 2 g/:raw-html:`cm3`.
- **Denitrification Decay Rate [1/T]:** This represents the first-order
decay constant. This constant controls the amount of nitrate loss due
to denitrification. An approximate value may be obtained from the
literature (e.g., McCray, 2005). The default value is 0.008
day\ :sup:`-1`.
- **Nitrification Decay Rate [1/T]:** This is the first-order decay
constant for NH\ :sub:`4`\ :sup:`+`. This constant controls the
amount of ammonium loss due to nitrification. By default, the value
is 0.0001 day-1.
- **Phosphorus Parameters:** These parameters allow for modeling
of phosphate transport in the subsurface environment, considering both
its movement and interactions with soil particles. Accurate specification
of these parameters helps in simulating the behavior of phosphate,
ensuring a realistic assessment of its potential impact on groundwater
quality and the surrounding ecosystem.
a. :raw-html:`Concentration of PO4-P [mg/l]:` The initial concentration
of phosphate-phosphorus in the source plane.
b. :raw-html:`PO4-P Dispersivity αL [m]:` Longitudinal dispersivity for
phosphate-phosphorus. The default is 2.113 meters.
c. :raw-html:`PO4-P Dispersivity αTH [m]:` Horizontal transverse dispersivity
for phosphate-phosphorus. The default value is 0.234 meters.
d. :raw-html:`Rprecip [mg/kg1/day]:` Represents the rate of precipitation for phosphate.
The default value is 0.002 mg/kg/day.
- **Sorption isotherm:** The sorption isotherm defines how phosphate interacts
with soil particles, either through a linear relationship or via Langmuir adsorption,
which accounts for both the affinity of phosphate to soil and the maximum capacity
of soil to adsorb phosphate.
**Linear:** The linear option assumes a constant, proportional relationship between
phosphate concentration and soil adsorption.
- **Linear distribution coefficient [L/kg]:** Represents the linear relationship
between adsorbed phosphate and its concentration in the solution. The default
value is 15.1 L/kg.
**Langmuir:** The Langmuir option models phosphate adsorption with a fixed maximum
capacity and varying affinity.
- **Langmuir coefficient [L/mg]:** Indicates the affinity of phosphate for adsorption
sites. The default value is 0.2 L/mg.
- **Maximum sorption capacity [mg P/kg]:** The total amount of phosphate that can be
adsorbed onto the soil surface at saturation. The default value is 237 mg P/kg.
.. note::
**Choosing Between Linear and Langmuir Sorption Isotherms:**
The choice between linear and Langmuir sorption isotherms depends on the specific
conditions of the study area. **Linear sorption** is recommended when the phosphorus
concentration is less than or equal to 10 mg/L, as it provides a simpler and proportional
model suitable for lower concentrations (McCray et al. 2005). For higher concentrations or
when adsorption sites are nearing saturation, **Langmuir sorption** is preferred because it
accounts for the maximum adsorption capacity and varying affinity of phosphate for soil particles.
Outputs
-------
The raster output(s) contain the concentration distribution of the
calculated plumes. An additional file, the “\_info” shapefile, is saved
in the disk location as the plume’s raster, with the same name and
having the “\_info” suffix. The “\_info” file contains points
corresponding to each source location. Each point has attributes that
describe the plume corresponding to that location (i.e., the parameters
used to calculate the plume, the warping, and post-processing methods,
to name a few). Since the Load Estimation Module uses some of this
information, the values in the attribute table should not be modified
manually. For reference purposes, the field descriptions of the “\_info”
file are given in Table 4‑2. In the table, the Load Estimation Module
uses the fields indicated with an asterisk to calculate loads. The
fields not used for calculation are for informational/archival purposes.
They should not be modified as they serve to record the parameters used
for each plume.
Additionally, the presence and consistency of the fields are checked to
ensure the parameters exist in the data. There are two options for plume
outputs. The first option is the default. The second option is enabled
by checking the box for the :raw-html:`Consideration of NH4-N`. The raster
output options are as follows:
- :raw-html:`Output Plumes of NO3-N (raster):` This is the name of the output
raster file of the :raw-html:`NO3-` concentration plumes. Note
that the “_info” shapefile has the same file name and location as the
raster.
- :raw-html:`Output Plumes of NH4-N (raster):` This is the file name and
location of the optional raster for the :raw-html:`NH4+` plumes.
Note that the “_info” shapefile has the same file name and location as
your raster.
- :raw-html:`Output Plumes of P (raster):` This is the name of the output raster file
for phosphate :raw-html:`(PO43-)` concentration plumes, showing
the spatial distribution of phosphorus concentrations. Similar to the other
outputs, the associated “_info” shapefile has the same file name and location as
the raster.
.. raw:: html
Table 4‑2: The field descriptions for the plumes auxiliary file.
+-------------------------+--------------------------------------------+
| **Field Name** | **Description** |
+=========================+============================================+
| PathID | This is the PathID of the flow paths that |
| | generate a particular plume. Values in |
| | this field correspond to values of the |
| | PathID field of Table 2‑1. |
+-------------------------+--------------------------------------------+
| Is2D | 1 – Indicates the plume is pseudo 3D. |
| | |
| | 0 – Indicates the plume is fully 3D (not |
| | currently supported). |
+-------------------------+--------------------------------------------+
| domBdy | – The source plane has a specified mass |
| | input rate. |
| | |
| | – The source plane has a specified Z |
| | dimension. |
+-------------------------+--------------------------------------------+
| decayCoeff | The decay coefficient. |
+-------------------------+--------------------------------------------+
| avgVel | The velocity value. It is obtained by |
| | averaging along the flow path. |
+-------------------------+--------------------------------------------+
| avgPrsity | The porosity value. It is obtained by |
| | averaging along the flow path. |
+-------------------------+--------------------------------------------+
| dispL | The longitudinal dispersivity. |
+-------------------------+--------------------------------------------+
| dispTH | The transverse-horizontal dispersivity. |
+-------------------------+--------------------------------------------+
| dispTV | This is for the transverse-vertical |
| | dispersivity that is not currently |
| | supported. |
+-------------------------+--------------------------------------------+
| sourceY | The Y source dimension. |
+-------------------------+--------------------------------------------+
| sourceZ | The Z source dimension. |
+-------------------------+--------------------------------------------+
| MeshDX | This mesh is the plume cell size in the |
| | x-direction (same as the MeshDY). |
+-------------------------+--------------------------------------------+
| MeshDY | This mesh is the plume cell size in the |
| | y-direction (same as the MeshDX). |
+-------------------------+--------------------------------------------+
| MeshDZ | This mesh is the plume cell size in the |
| | z-direction (same as the sourceZ). |
+-------------------------+--------------------------------------------+
| plumeTime | The plume time is the time at which the |
| | plume is calculated. This value is -1 for |
| | steady-state plumes (only steady-state |
| | solutions are supported). |
+-------------------------+--------------------------------------------+
| pathTime | The total time that flow takes from the |
| | start of the flow path to the end. |
+-------------------------+--------------------------------------------+
| plumeLen | Plume length represents the length of the |
| | plume in map units. |
+-------------------------+--------------------------------------------+
| pathLen | The path length is the total length of the |
| | flow path. |
+-------------------------+--------------------------------------------+
| plumeVol | Plume volume is the total volume |
| | calculated by summing the volumes of the |
| | individual plume cells. Each plume cell |
| | has dimensions MeshDX \* MeshDY \* MeshDZ. |
+-------------------------+--------------------------------------------+
| massInRate\* | The mass input rate of nitrate is from the |
| | Domenico constant concentration plane due |
| | to advective and dispersive flow. This |
| | number is calculated based on an |
| | analytical solution. |
+-------------------------+--------------------------------------------+
| massDNRate\* | The nitrate mass removal rate is due to |
| | denitrification. This value is calculated |
| | for each plume cell using the definition |
| | of first-order decay. |
+-------------------------+--------------------------------------------+
| srcAngle | The orientation of the Domenico source |
| | plane is in degrees clockwise from north. |
+-------------------------+--------------------------------------------+
| Warp | This field represents the warping |
| | algorithm utilized. |
| | |
| | 0 – Spline |
| | |
| | 1 – Polyorder1 |
| | |
| | 2 – Polyorder2 |
+-------------------------+--------------------------------------------+
| PostP | The post-processing method. |
| | |
| | 0 – None |
| | |
| | 1 – Medium |
| | |
| | 2 – Full |
+-------------------------+--------------------------------------------+
| msRtInNMR | This rate is the mass input rate of |
| | nitrate from the Domenico constant |
| | concentration plane due to advective and |
| | dispersive flow. The method that |
| | calculates this is similar to numerical |
| | modeling software in which the inflow is |
| | calculated on a cell-by-cell basis, given |
| | the size of the source plane, groundwater |
| | flow velocity, and concentration |
| | gradients. The field is for information |
| | purposes, as it is not used in |
| | calculations. |
+-------------------------+--------------------------------------------+
| C_NO3 | The source concentration of |
| | NO\ :sub:`3`-N. |
+-------------------------+--------------------------------------------+
| C_NH4 | The source concentration of NH\ :sub:`4`-N |
+-------------------------+--------------------------------------------+
| C_PO4 | The source concentration of PO\ :sub:`4`-P |
+-------------------------+--------------------------------------------+
| VolFac | The volume conversion factor. |
+-------------------------+--------------------------------------------+
| nextConc | It is an approximate value of the |
| | concentration gradient at the source. This |
| | value corresponds to the cell |
| | concentration located at x=MeshDX, y=0. |
+-------------------------+--------------------------------------------+
| threshConc | The concentration threshold value. |
+-------------------------+--------------------------------------------+
| WBId_plume\* | Records the FID of the water body that the |
| | plume discharges to. If the plume does not |
| | reach a water body, this value is -1. |
+-------------------------+--------------------------------------------+
| WBId_path\* | Records the FID of the water body that the |
| | flow path reaches. If the flow path does |
| | not reach a water body, this value is -1. |
+-------------------------+--------------------------------------------+
Troubleshooting
---------------
Table 4‑3 lists possible issues encountered during model execution,
probable causes, and possible solutions. Note that the error messages
may appear for reasons other than those listed. If you cannot find a
solution to the issue, then please submit a [New issue] in the
ArcNLET-Py GitHub repository (`Issues · ArcNLET-Py/ArcNLET-Py ·
GitHub `__) as
described in the GitHub instructions at `Creating an issue - GitHub
Docs `__.
.. raw:: html
Table 4‑3: The Transport Module troubleshooting guide.
+---------------------+-----------------------+-----------------------+
| **Error** | **Cause** | **Solution** |
+=====================+=======================+=======================+
| Depending on the | The system has | Free up memory by |
| choice of | insufficient memory | closing other |
| parameters, plume | or disk space. | programs. |
| calculation may | | |
| fail if there are | | Split up the input |
| many sources. | | file (paths or |
| | | sources) into |
| | | multiple parts |
| | | (either split up the |
| | | point sources or the |
| | | particle paths). |
+---------------------+-----------------------+-----------------------+
| Junk is output in | Warping may succeed | Try a different |
| the plume’s raster | in specific | warping method or |
| after warping. | configurations of the | different control |
| | warping control | point spacing. |
| | points (e.g., when | |
| | many points fall on a | |
| | path that is almost a | |
| | straight line), but | |
| | the plume raster | |
| | consists of garbled | |
| | data. | |
+---------------------+-----------------------+-----------------------+
| Some plumes are not | Warping fails due to | Decrease the value of |
| calculated. | insufficient control | the Plume cell size |
| | points if the plume | parameter. |
| | is too short. | |
| | | Move the OSTDS point |
| | The OSTDS point may | outside or modify the |
| | be inside a water | water body boundary |
| | body. | if appropriate. |
| | | |
| | | If a plume is not |
| | | calculated for any |
| | | reason, the input |
| | | load to the system |
| | | due to that source is |
| | | ignored. |
+---------------------+-----------------------+-----------------------+