This Technical Practice Update (TPU) proposes a watershed rating methodology that combines and expands existing elements used to assess the sustainability of a watershed, including human use of physical characteristics, water and wastewater treatment facilities, and significant industrial facilities. Inherent in these discussions is the concept that human activity, at a minimum, should only use nature's resources at a rate at which they can be safely replenished naturally so that future generations can meet their own needs. It has now been proposed that it may be possible to apply certification to an entire watershed. This TPU tries to show how steps might be taken in this direction and to address how a foundation might be established that could provide the basis for a subsequent certification process. Published by WEF. 2009. Electronic download. 22 pages.