The purpose of the Western Washington Hydrology Model (WWHM2012) is to design stormwater control facilities so they can best mitigate the effects of increased runoff (peak discharge, duration, and volume). This model can also inform facility developers and managers on the effects likely to result from proposed land-use changes that impact nearby natural streams, wetlands, and other water courses.
We released WWHM2012
WWHM2012 is an updated version of Western Washington Hydrology Model that includes several new elements related to Low Impact Development (LID). The last generation of the Western Washington Hydrology Model (WWHM3) could not model LID features/facilities. See a list of the changes between Model 3 to 2012.
Latest version of the model
To install the current version of the WWHM2012, download and install first the "WWHM Program" file, then the "Map Data" file below.
The Model will be updated as we receive comments and make improvements.
Archive of all 2012 versions
All versions of the WWHM2012 program are available in our WWHM archive.
Western Washington Hydrology Model users manual
WWHM 2012 trainings available (for a fee)
For information on training classes on Western Washington Hydrology Model WWHM2012 please contact Dan Morris at the AGC Education Foundation at 206-284-4500.
You may also go to the AGC Education Foundation website and navigate to find and register for WWHM2012 training classes. Class schedules are based on the number of people interested in training.
More information about the 2012 version of the model
Model version WWHM2012 provides:
- A uniform technology and methodology for the 19 counties of Western Washington
- A more accurate methodology than single-event design storms
- An easy-to-use software package
Model version WWHM2012 is based on:
- Continuous simulation hydrology (HSPF)
- Washington's long-term recorded precipitation data
- Measured pan-evaporation data
- Historic vegetation (for pre-developed conditions)
- Regional HSPF parameters
Parameter values can be modified to simulate local conditions and meet the needs of each county or region.
Join the Western Washington Hydrology Model email listserv for news, including new version releases.