The purpose of forecasting is "to identify patterns in natural systems and human behavior and to discover relationships among variables and systems so we can estimate the timing, nature, and magnitude of changes in future conditions" (Institute for Water Resources 1996:146).
Two conditions are again established:
· The without-project condition. Projecting into the future, what will the resources be like if no project is constructed, the proposed action is not taken.
· The with-project condition. In this case, what will the resources be like if the project or action does occur?
The same resources are addressed in both conditions. How they might interact with their environment may be different under the two conditions, however.
The Planning Manual, beginning on page 146 of the pdf file, contains an overview of suggested techniques. Techniques are summarized in Table 25 as shown below.