New England
(01)
Missouri (10)
California
Mid-Atlantic
(02)
South Atlantic-Gulf
(03)
Puerto Rico
Caribbean (21)
Great Lakes
(04)
Ohio(05)
Tennessee
(06)
Upper Mississippi (07)
Souris-Red-Rainy
(09)
Lower Mississippi
(08)
Texas-Gulf
(12)
Arkansas-White-Red (11)
Pacific Northwest
(17)
Rio Grande
(13)
UpperColorado
(14)
LowerColorado
(15)
(18)
Great Basin
(16)
Alaska(19)
Hawaii(20)
Water-resources regions of the United States