RiverSim provides great freedom as to the choice of units and the time step for creating and running a model.

The graphic shows the menu to get at the default units and timing information. Choosing "Default Units" from the menu gets the following dialog:

The combo boxes function as expected and you may choose any convenient set of units. You need not be consistent between English and SI units.

The scale factor allows you to choose a decade multiplier. So, if you wish to work in millions of cubic meters or thousands of acre feet, this is possible. Note that the units you select are for display and reporting only. The simulator runs internally on a consistent set of units.

One of the selections under Flow is AFF which means acre-feet of flow, a unit of volume. This is to be interpreted as acre-feet per time step.

Selecting "Initial Values" from the menu gets the following dialog. This is simply the standard slot display for the storage slots of all the reservoirs in the system. It is provided as a convenience. You can do the same thing by double clicking on each reservoir in the workspace and setting beginning storage in that display.

Selecting "Timers" from the menu gets the following dialog:

There are two group boxes on this dialog.

• Model Time: This area sets the simulation time step and the start time for the model. RiverSim will run on any step from one hour up to one month. It is important to note that changing the time step on an existing model will erase all existing time series. This is because RiverSim has no way to disaggregate a time series.
• Control Cycle: This area sets the control cycle for the model. Briefly, many river basins reuse the same operating rules in a repeating pattern. This may be anywhere from monthly within an annual cycle for planning purposes to hourly within a daily cycle for peaking hydropower. RiverSim allows complete control over this process.