| Altamaha Watersheds |
| Arctic Alaska |
| Arkansas/Red Rivers |
| Beaufort/Chukchi Seas |
| Bering Sea/Aleutian Islands |
| Bristol Bay/Kodiak |
| Caribbean |
| Central Gulf Watersheds |
| Central Valley of California/San Francisco Bay |
| Chesapeake Bay/Susquehanna River |
| Columbia Basin |
| Connecticut River/Long Island Sound |
| Delaware River/Delmarva Coastal Area |
| East Texas |
| Edwards Plateau |
| Florida Panhandle Watersheds |
| Gila/Salt/Verde Rivers |
| Great Lakes |
| Gulf of Maine Rivers |
| Hudson River/New York Bight |
| Interior Alaska |
| Interior Basin |
| Klamath/Central Pacific Coast |
| Lake Champlain |
| Lower Colorado River |
| Lower Mississippi River |
| Lower Missouri River |
| Lower Rio Grande |
| Middle and Upper Rio Grande |
| Mississippi Headwaters/Tallgrass Prairie |
| Missouri Main Stem |
| North Pacific Coast |
| North Pacific/Gulf of Alaska |
| Northwest Alaska |
| Ohio River Valley |
| Ozark Watersheds |
| Pacific Islands |
| Pecos River |
| Peninsular Florida |
| Platte/Kansas Rivers |
| Roanoke/Tar/Neuse/Cape Fear Rivers |
| Savannah/Santee/Pee Dee Rivers |
| South Central Alaska |
| South Florida |
| Southeast Alaska |
| Southern Appalachians |
| Southern California |
| Tennessee/Cumberland River |
| Texas Gulf Coast |
| Upper Colorado River |
| Upper Mississippi River/Tallgrass Prairie |
| Upper Missouri/Yellowstone and Upper Columbia Rivers |
| Yukon-Kuskokwim Delta |
| <all other values> |