Region
- United States 1,398 results
- Colorado 397 results
- California 117 results
- Great Lakes (North America) 103 results
- Florida 55 results
- West (U.S.) 46 results
- Chesapeake Bay (Md. and Va.) 41 results
- Chesapeake Bay Watershed 40 results
- Colorado River Watershed (Colo.-Mexico) 39 results
- Long Island Sound (N.Y. and Conn.) 32 results
- Massachusetts 29 results
- Texas 26 results
- Great Lakes Region (North America) 22 results
- New York (State) 22 results
- Washington (D.C.) 21 results
- Europe 20 results
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- Arizona 18 results
- Denver Metropolitan Area 18 results
- Idaho 18 results
- Michigan 18 results
- Oregon 18 results
- Colorado River (Colo.-Mexico) 17 results
- Kansas 17 results
- Louisiana 17 results
- Minnesota 17 results
- Ohio 17 results
- European Union countries 16 results
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- Montana 15 results
- Alaska 14 results
- Canada 14 results
- Hawaii 14 results
- Missouri 14 results
- Pennsylvania 14 results
- Utah 14 results
- Atlantic Ocean 13 results
- Georgia 13 results
- Iowa 13 results
- Mississippi River Watershed 13 results
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- Great Lakes Watershed (North America) 12 results
- Mexico, Gulf of 12 results
- North America 12 results
- Washington (State) 12 results
- Indiana 11 results
- Pontchartrain, Lake, Watershed 11 results
- Pontchartrain, Lake, Watershed (La.) 11 results
- West Virginia 11 results more…