\section{Simulation Tools - A Decision Consequence Estimation Component}
The purpose of a simulation in the context of this document is to predict the response of a system to the decisions; that is what is the anticipated state of the system after the decisions have been applied.  Did the decisions improve the situation, or make it worse, or no detectable change.
\subsection{Simulation and Models}
define a model



\subsubsection{Example}
\subsection{Statistical Models}
\subsubsection{Example}
\subsection{Analog Models}
Analog models are models where analogs of the real system to be studied are employed.
Column, Jar, and bench-scale studies in Environmental Engineering are examples of analog (and physical) models of a real system.
Flume and estuary  scale physical models are examples of analog (and scaled) models of a real system.
Electric circuit analogs have been built to simulate behavior of river systems and groundwater aquifers -- actual instances of these kinds of models are today only likely to be found in museums; computer models have largely replaced these kind of analog models.

In general analog models are outside the scope of this document, they are useful, they are expensive, and they are uncommon (with the exception of the Environmental Engineering laboratory models).
\subsubsection{Example}
\subsection{Digital Models}
\subsubsection{Example}
Use an on-line network simulator to make a decision.  
\subsection{Readings}
\subsection{Exercises}