\documentclass[10pt,letterpaper, final]{report} % \documentclass{} required in all files

\usepackage{../preamble/myWEPS} % This is now our single preamble file inclusion (it assumes a “.sty” file extension)

\begin{document}

\subsection{Skill Building} \label{subsec:Skill_Building_9}
The \textbf{X-length} is the longest (one dimension) distance from a stable boundary
to the opposite side of the field running east-west with the orientation angle set at 0\textdegree.
The \textbf{Y-length} is the longest (perpendicular to the X-length) distance from a stable boundary
to the opposite side of the field running north-south with the orientation angle set to 0.
These are the \textbf{unsheltered distances} which WEPS uses to calculate the erosion rate.
A \textbf{stable boundary} is one that stops surface creep and saltation phases of wind erosion.
A grass strip at least 13 feet wide and 1.5 feet high is an example of a stable boundary.
Vegetation width, height, and porosity are to be considered when declaring a stable boundary.
Most barriers, such as a windbreak, also can function as a stable boundary.

This exercise is intended to assist the user in selecting the correct distance to enter
for the X-length and the Y-length in the Simulation Region panel of the WEPS interface.

\subsection{Scenario} \label{subsec:Scenario_9} 

\begin{itemize}

\item{A 40-acre field (shown in light tan) is to be evaluated for wind erosion.
The remaining land (green) is not controlled by the owner of the 40 acres
and the management on this remaining land cannot be changed by the owner of the 40-acre field.
The remaining land may however contribute to the wind erosion process on the 40-acre field.}
\item{The green land (one section in size, 640 ac) has a road on all sides
with a 50-ft band of green vegetation (grass, 1.5 ft perimeter buffer).}
\item{The non-erodible buffer is represented in dark brown.}
\item{Both the 40 acres and the remaining 600 acres are farmed in a winter wheat-summer fallow, 
conventional tillage rotation.}

\end{itemize}

\textbf{Question}: Which of the following selections is the correct X-Length and Y-Length combination
to evaluate or enter in the Simulation Region panel on the WEPS interface?

\begin{itemize}
\item{\textbf{A} X=2640 ft by Y=1320 ft}
\item{\textbf{B} X=5280 ft by Y=3960 ft}
\item{\textbf{C} X=1320 ft by Y=1320 ft}
\item{\textbf{D} X=5280 ft by Y=5280 ft}
\end{itemize}

\begin{figure}[H]
\centering
	\includegraphics[scale=0.6]{images/Example_9/Ex9-1a.jpg}
\end{figure}


In WEPS, wind directions are simulated to vary from day to day throughout the simulation.
Because the management outside the field is not controlled by the same owner for conservation planning purposes,
the unsheltered distance should be the \textbf{longest distance} from a stable boundary
through the length of the field to the down-wind edge of the field.
On the X axis, the longest distance (X-Length) starts at the east boundary and extends west
all the way through the 40 acre field (5280 ft).
On the Y axis, the longest distance (Y-Length) starts at the south boundary and extends north
all the way though the 40 acre field (3960 ft).
Therefore, the dimensions (X-Length, Y-Length, and acres) entered on the WEPS interface will 
be larger than the actual field for this scenario.
Thus, the \textbf{Answer} is: \textbf{B}

\begin{figure}[H]
\centering
	\includegraphics[scale=0.8]{images/Example_9/Ex9-2.jpg}
\end{figure}

By using the Critical Dominant Soil within the field, we can ensure that we are considering the 
most erodible part of the field.
By controlling wind erosion on that portion, it is highly likely 
that erosion will controlled on the entire field.

To demonstrate this in a real world example
(note that this example site does not exactly represent the scenario mentioned above,
but it is close enough for demonstration purposes), let's look at the following scenario:
\begin{itemize}
\item{Select a field located approximately at \textbf{37.23823º N, 100.17985º W} in Meade county, Kansas.}
\item{Specify a field size of \textbf{40 ac} square (\textbf{1320 ft x 1320 ft})}
\item{Select the \textit{CRLMOD Managements} CSIP service from the management dropdown choice list.
Go into the \textit{CMZ 40} management folder
and then into the \textit{b. Multi-year Rotation Templates} folder.
From there, select the \textbf{Wheat, grain; 1 yr fallow, sweep, CMZ40} two year management rotation.}
\item{Select the most erosive soil via the CSIP Soil Service for the field located approximately at
\textbf{37.23823º N, 100.17985º W}
which is the \textbf{Manis\_KS119\_2689\_90\_CL} soil
(\cref{{fig:Map showing the soil map units of a field_1}}.}
\end{itemize}

\begin{figure}[H]
\centering
	\includegraphics[scale=1.4]{images/Example_9/WebSoilSurvey_map.jpg}
\caption{WebSoilSurvey Map showing soil map units of a field.}
\label{fig:Map showing the soil map units of a field_1}
\end{figure}

\textbf{Step 1}: Make a WEPS Run with the 40 acre field size specified.
The Run Summary is presented in \cref{fig:Run_Summary_results_for_40_acre_field}.

\begin{figure}[H]
\centering
	\includegraphics[scale=1.8]{images/Example_9/Run_Summary_40ac_Ex9.jpg}
\caption{Run Summary results for 40 acre field only.}
\label{fig:Run_Summary_results_for_40_acre_field}
\end{figure}

\textbf{Step 2}: Change the field size to an \textbf{X-Length = 5280 ft} and a \textbf{Y-length = 3960 ft} (480 acres).
The field shape must be set to \textbf{Rectangle} to make these changes, if it is not already set to that shape.

\textbf{Step 3}: Make another WEPS Run with the 480 acre field size specified
The Run Summary is presented in \cref{fig:Run_Summary_results_for_480_acre_field}.


\begin{figure}[H]
\centering
	\includegraphics[scale=1.8]{images/Example_9/Run_Summary_480ac_Ex9.jpg}
\caption{Run Summary results for 480 acre field (stable boundary).}
\label{fig:Run_Summary_results_for_480_acre_field}
\end{figure}

Note that the erosion rate from the field went from 0.7 tons/ac per year rate for the 40 acre field only
to 2.4 tons/ac per year for the 480 ac field size to reach a non-erodible boundary.
Our erosion estimate is almost 3.5 times greater for the larger field size.
In this case, the management practices, even though significant tillage is being conducted,
still keeps sufficient residue on the surface during the fallow season at this site,
to keep it under the Soil Loss Tolerance value, even for the larger sized field simulated.

However, it still demonstrates the impact homogeneous management practices have on large fields
and there potential affect on adjacent fields if there are no non-erodible boundaries present
to reduce or eliminate the saltation process on the site.
If the site was more susceptible to erosion, e.g. less residue cover being maintained on the site
or the erosive winds were more extreme during that period, the difference in erosion rates
for the two simulations would have been much greater.
This is a prime example where a reduction in the distances to non-erodible boundaries
would significantly reduce wind erosion susceptibility and its magnitude when it does occur.
A suitable example practice here would be strip cropping the large field
by alternating the fallow and crop growth periods in this two year rotation.

\end{document}