DHI-WEH produces some excellent hydrology, hydraulic, and water quality software applications. Unfortunately, these are some of the most expensive such software applications available anywhere.
MIKE SWMM (from DHI-WEH) is now available free of charge to anyone who would like to use it: freeware. It is based on SWMM4.4x and does not support the latest version of SWMM (5.x).
The company is focusing development resources on MIKE URBAN, phasing out MIKE SWMM, MOUSE, and MIKE STORM.