SWMM's rain gauge objects can utilise rainfall data stored in external rainfall files. The program currently recognises the following formats for storing such data:
DSI-3240 and related formats which record hourly rainfall at U.S. National Weather Service (NWS) and Federal Aviation Agency stations, available online from the National Climatic Data Centre (NCDC) at www.ncdc.noaa.gov/oa/ncdc.html.
DSI-3260 and related formats which record fifteen minute rainfall at NWS stations, also available online from NCDC.
HLY03 and HLY21 formats for hourly rainfall at Canadian stations, available online from Environment Canada at www.climate.weatheroffice.ec.gc.ca.
FIF21 format for fifteen minute rainfall at Canadian stations, also available online from Environment Canada.
A standard user-prepared format 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.
An excerpt from the user-prepared format might look as follows:
STA01 2004 6 12 00 00 0.12
STA01 2004 6 12 01 00 0.04
STA01 2004 6 22 16 00 0.07
When a rain gauge is designated as receiving its rainfall data from a file, the user must supply the name of the file and the name of the recording station referenced in the file. For the standard user-prepared format, the rainfall type -e.g. intensity or volume, recording time interval, and depth units must also be supplied as rain gauge properties. For the other file types, these properties are defined by their respective file format and are automatically recognised by SWMM.