The Watershed Treatment Model (WTM) 2013 helps users to estimate benefits from a wide range of stormwater runoff and pollutant removal practices. This is an older version that is compatible with 32 bit machines and early 64 bit versions.

There is a May, 2020 update to the WTM that upgrades the macros in the “WTM 2013 off the shelf – 64 bit” file to be compatible with most modern computers. It also addressed some inconsistencies between levels of implementation described as “percentage” versus “fraction” and made some edits to the “Results-copy” tab.

Some computers may experience errors or conflicts with the older 32 bit or newer 64-bit version, either due to a windows or VBA version or build date, and on some older machines. For those users, the “WTM 2013 off the shelf – no macros” version is available. The calculations in this version are exactly the same as in the 64-bit option, but the user is not able to use check boxes to reveal only portions of each sheet.