There are 3 conservation authorities in Halton Hills. This includes the watersheds of Credit Valley Conservation, Conservation Halton, and Grand River Conservation Authority. Within these areas are subwatersheds. Within the subwatersheds are areas called catchments. The Subwatershed Impact Study (SIS) listed here deals with stormwater management within the catchment area. The study looks to all watersheds so that impacts of management do not affect other areas. The Scoped Subwatershed Plan for the 401 Corridor has established watershed policies, objectives, constraints and watershed management techniques.