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Region
- United States109
- Wisconsin25
- Minnesota19
- Mississippi River Watershed19
- High Plains Aquifer15
- Illinois River Watershed13
- New Jersey11
- Florida10
- CaliforniaSan Joaquin River Watershed9
- OregonWillamette River Watershed9
- Ozark Mountains9
- Red River of the North Watershed9
- Arizona8
- North Carolina8
- CaliforniaTulare Lake Watershed7
- Iowa7
- Middle West7
- New England7
- Potomac River Watershed7
- TexasTrinity River Watershed7