Rainfall

Commonly, LTCS's are used to test sewer models with many years worth of rainfall data. Although, you can manually enter in this data directly into the Storm Data Group Library, Drainage and Utilities now has the capability to reference external rainfall files when using the SWMM and 2D engines. This functionality eliminates the necessity of entering years worth of rainfall data into the Drainage and Utilities Storm Libraries and allows you to directly access rainfall stored in many common formats including:

• DSI-3240
• DSI-3260
• HLY03, HLY21
• FIF21
• And a generic SWMM specific format which works as follows where each line of the file contains the station ID, year, month, day, hour, minute, and non-zero precipitation reading, all separated by one or more spaces

STA01 2004 6 12 00 00 0.12

STA01 2004 6 12 01 00 0.04

STA01 2004 6 22 16 00 0.07

For more information on how SWMM utilizes external rain files see the SWMM user manual section 11.3 here: http://www.epa.gov/ednnrmrl/models/swmm/epaswmm5_user_manual.pdf

When setting up a reference to a rainfall file in the Storm Data dialog, note that not all data is required for all data types. For example when using the SWMM specific format, you will need to set the Rain Data File Type, the Station ID and the interval, for other file types this data may be implicit in the file. Also, if the Rain Data File contains multiple stations you can create multiple references to the same file, by clicking the add button in the Rain File Storm Data section.

When editing a definition of the Rain File type, the tabbed area of the dialog contains the following controls:

Storm Data Input Tab

Rain File: Allows you to select the desired SWMM rain file.

Rain Data File Type: Allows you to select the type of data stored in the selected rain file.

Rain Units: Allows you to select the unit for the data in the selected rain file.

Rain File Storm Data Table: Click the New button to add a row to the table; click Delete to remove the currently highlighted row from the table. The table consists of the following columns:

• Label: The label for the storm data.
• Station ID: The station ID for the storm data.
• Time Interval: The time interval for the storm data.
• Snow Catch Factor: Allows you to enter the SWMM snow catch factor.

Notes Tab

This tab contains a text field that allows you to enter descriptive notes that will be associated with the currently highlighted storm data definition.

Library Tab

This tab displays information about the storm data definition that is currently highlighted in the list pane. If the storm data definition is derived from an engineering library, the synchronization details can be found here. If the storm data definition was created manually for this model, the synchronization details will display the message Orphan (local), indicating that the storm data definition was not derived from a library entry.