The program must manage many different kinds of data that are part of a wide variety of components. Part of the management is the saving and display of the data entered by the user. The remainder of the management is the use of the data during a compute.

Saving Properties

The program uses the concept of the current component to manage saving updates or changes to properties. The current component is the item in the project that is currently selected in the Watershed Explorer. For example, if you click on a Subbasin icon in the Watershed Explorer it will become highlighted, and its editor will be shown in the Component Editor. The subbasin becomes the current component at that moment. You may make changes to the properties of the subbasin on any of the tabs in the Component Editor. When you switch between tabs, any changes are automatically updated in the subbasin. The changes are also updated when you leave the tabs and click anywhere else in the program interface. Even though the updates are made in the subbasin properties, the changes are not saved to disk. Updates and changes are only saved to disk when the project is saved. You can save the project two different ways.

The first way to save all pending changes is from the File menu. Click on the File menu and then select the Save command. All components currently open in the project will be saved to disk, including the current Basin Model with its hydrologic elements, current Meteorologic Model, current Control Specifications, and all other project components.

The second way to save all pending changes is from the toolbar. Click the Save Current Project button. All components in the project will be saved to disk.

Number Formatting

Each country of the world has socially accepted conventions for formatting numbers. It would be difficult for the program to support every single convention in use around the world. However, one important factor is the symbol used for the decimal separator. For example, in the United States a number would typically be formatted as follows:


In Austria the same number would usually be displayed as follows:


Either format can be selected using the program settings described in Program Settings. The setting is used to interpret all user input and to configure all displayed output data.

Date and Time Formatting

The formatting of dates and times is also subject to social convention. The program imposes some limitations to simplify the formatting of date and time information. All dates should specify a two-digit day, followed by the month abbreviation, and end with a four-digit year. For example, in the United States a date would be entered or displayed as follows:


The same date would be entered or displayed in France as follows:


Dates will be processed using the common month abbreviation according to the language and country selected in the program settings described in Program Settings. The selected choice will be used for displaying data information, for example, in computed results. The selected choice will also be used for interpreting input, for example, when specifying the start time of a simulation.

All times are formatted with the same rules regardless of any settings on the computer. A time should use two digits for the hour, followed by a colon, and end with two digits for the minutes. All times are assumed to be in an arbitrary local time zone that does not observe summer time (daylight savings in the United States). It uses 24-hour clock time instead of AM or PM notation. For example, time would always be displayed as:


Some status messages displayed by the program indicate when some event occurred. Those times also include seconds.

The date system used in the program follows the Gregorian calendar. This calendar entered use at the end of the day on 04 October 1582. It took many years for the calendar to gain wide-spread use in Europe. It eventually became the most common calendar in use around the world. One of the principal features of the calendar is the definition of leap year. Because the program does not implement the calendars that preceded it, the leap year rules defined in the Gregorian calendar are applied throughout all time. This means that for simulations with time intervals before 1582, the simulation results may show inconsistencies when compared to the calendar actually in use during those ancient historical times.

Units Conversion

Almost all initial conditions and parameter data for the various methods included in the program require units. For example, hydraulic conductivity has units of either millimeters per hour (mm/hr) or inches per hour (in/hr) depending on the unit system of the Basin Model. The unit system is one of the properties of the Basin Model and Meteorologic Model. If the system international unit system is selected for a Basin Model, then the hydraulic conductivity should be entered in mm/hr. However, the conductivity should be entered in in/hr if the U.S. customary unit system is selected. The units of an initial condition or parameter are shown in parenthesis after the label.

The value of initial conditions and parameter data are automatically converted when the unit system of a Basin Model or Meteorologic Model is changed. For example, suppose a Basin Model used the U.S. customary unit system and a hydraulic conductivity was entered as 0.23 in/hr. If the unit system were changed to system international, the conductivity would be automatically converted to 5.84 mm/hr. The conversions are performed according to standards specified by the National Institutes of Standards and Technology (Taylor 1995).

Time-series data, paired data, and grid data components each have their own unit system based on the units of the data. The unit system is determined automatically from the units of the data. For example, a discharge time-series gage with units of cubic meters per second (M3/S) will be in the system international unit system. The units are selected by the user for manual entry data, but are read automatically from the record header for external DSS data. Data is automatically converted to the correct unit system during a compute.


Time-series data and gridset data are usually defined with a fixed time interval, though some data may be defined on an irregular basis. All of the different types of simulations happen with a fixed time interval, as specified in the control specifications. When the time interval of the time-series or gridset data does not match the time interval of the compute, the data is automatically interpolated. A linear interpolation in time is used.

Paired data components use a limited number of points to represent a curve, such as a storage-discharge curve. However, the curve represents continuous data. Linear interpolation is used when a dependent value is required for an independent value between two specified values. The interpolation is performed between the dependent values corresponding to the closest available independent values on each side of the requested value. Some paired data components use irregularly spaced values to represent an annual pattern, such as a groundmelt pattern. Linear interpolation in time is used on these components.