Major U.S. Watersheds

This menu includes major watersheds: the Albemarle and Pamlico Sounds, Chesapeake Bay, Columbia River Basin, Delaware Bay, Delaware River Basin, Great Lakes, Long Island Sound, Lower Columbia River Basin, Mississippi-Atchafalaya River Basin, Mobile Bay, Puget Sound, San Francisco Bay, and Tampa Bay. Many of these watersheds consist of several HUC-12 codes. Maps of these watersheds are available on the User Guides/Technical Documents tab.

This menu also provides options to search watershed boundaries defined by:

USGS: The US Geological Survey classifies watersheds in the US and Caribbean into 21 regions, represented by a 2-digit Hydrologic Unit Code (HUC).

Large Aquatic Ecosystems (LAEs) Program: EPA's Office of Wetlands, Oceans & Watersheds classifies LAEs to include multiple small wetersheds and water resources within a large geographic area that provides significant resources or services, such as food supply,recreation and tourism, groundwater recharge, flood management, air purification, nutrient cycling, and wildlife habitat.

National Estuaries Program (NEP): The NEP identifies nationally significant estuaries of the US for protection and restoration. EPA administers the NEP, but program decisions and activities are carried out by committees of local government officials, private citizens, and representatives from other federal agencies, academic institutions, industry, and estuary user-groups. Estuaries are selected for inclusion in the program through a nomination process. There are currently 28 estuary programs implemented in the U.S.