Water resource region facts for kids

A water resource region is a way the United States Geological Survey (USGS) divides the United States into large areas. Think of it like drawing big lines on a map to show where all the water flows!

Each region is a huge area where all the rain and snow eventually drains into one main river, or a group of rivers that flow into the same ocean or sea. The U.S. is split into 21 of these main water regions.

The 21 main water resource regions of the United States.

Exploring U.S. Water Regions

The United States is divided into 21 major water resource regions. Each region is like a giant bowl where all the water collects and flows in a certain direction. This helps scientists understand how water moves across the country. Below is a list of these regions, showing where they are and where their water ends up.

Region Number	Region Name	Where the Water Goes	States Included	Size (approx.)	Map
01	New England	Water flows into the Bay of Fundy, the Atlantic Ocean (near Maine and Connecticut), Long Island Sound, and the Saint-François River (which goes to the Saint Lawrence River).	All of Maine, New Hampshire, Rhode Island, and parts of Connecticut, Massachusetts, New York, and Vermont.	73,753 sq mi (191,020 km2)
02	Mid Atlantic	Water flows into the Atlantic Ocean (from New York to Virginia), Long Island Sound, and the Richelieu River (which goes to the Saint Lawrence River).	All of Delaware, New Jersey, and Washington, D.C., plus parts of Connecticut, Maryland, Massachusetts, New York, Pennsylvania, Vermont, Virginia, and West Virginia.	106,334 sq mi (275,400 km2)
03	South Atlantic–Gulf	Water flows into the Atlantic Ocean (from Virginia to Florida) and the Gulf of Mexico (from Florida to Louisiana).	All of Florida and South Carolina, plus parts of Alabama, Georgia, Louisiana, Mississippi, North Carolina, Tennessee, and Virginia.	279,664 sq mi (724,330 km2)
04	Great Lakes	Water flows into the Great Lakes system and the Saint Lawrence River.	Parts of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin.	141,984 sq mi (367,740 km2)
05	Ohio	Water flows into the Ohio River Basin (but not the Tennessee River Basin).	Parts of Illinois, Indiana, Kentucky, Maryland, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia.	162,916 sq mi (421,950 km2)
06	Tennessee	Water flows into the Tennessee River Basin.	Parts of Alabama, Georgia, Kentucky, Mississippi, North Carolina, Tennessee, and Virginia.	40,908 sq mi (105,950 km2)
07	Upper Mississippi	Water flows into the Mississippi River above where the Ohio River joins it (but not the Missouri River Basin).	Parts of Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, South Dakota, and Wisconsin.	189,968 sq mi (492,010 km2)
08	Lower Mississippi	Water flows into the Mississippi River below where the Ohio River joins it, and into coastal streams that go to the Gulf of Mexico.	Parts of Arkansas, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee.	106,741 sq mi (276,460 km2)
09	Souris-Red-Rainy	Water flows into Lake Winnipeg and Hudson Bay (in Canada).	Parts of Minnesota, North Dakota, and South Dakota.	90,759 sq mi (235,060 km2)
10	Missouri	Water flows into the Missouri River Basin, the Saskatchewan River Basin, and some smaller areas where water doesn't flow out to the ocean.	All of Nebraska and parts of Colorado, Iowa, Kansas, Minnesota, Missouri, Montana, North Dakota, South Dakota, and Wyoming.	520,960 sq mi (1,349,300 km2)
11	Arkansas-White-Red	Water flows into the Arkansas River, White River, and Red River Basins.	All of Oklahoma and parts of Arkansas, Colorado, Kansas, Louisiana, Missouri, New Mexico, and Texas.	247,988 sq mi (642,290 km2)
12	Texas-Gulf	Water flows into the Gulf of Mexico from Sabine Pass to the Rio Grande.	Parts of Louisiana, New Mexico, and Texas.	181,886 sq mi (471,080 km2)
13	Rio Grande	Water flows into the Rio Grande Basin and other areas where water doesn't flow out to the ocean.	Parts of Colorado, New Mexico, and Texas.	132,517 sq mi (343,220 km2)
14	Upper Colorado	Water flows into the Colorado River Basin above a specific point called Lee Ferry, and into the Great Divide closed basin.	Parts of Arizona, Colorado, New Mexico, Utah, and Wyoming.	113,347 sq mi (293,570 km2)
15	Lower Colorado	Water flows into the Colorado River Basin below Lee Ferry, and into the Gulf of California, plus some smaller areas where water doesn't flow out to the ocean.	Parts of Arizona, California, Nevada, New Mexico, and Utah.	140,146 sq mi (362,980 km2)
16	Great Basin	Water flows into the Great Basin within Utah and Nevada, which means it stays within the basin and doesn't reach the ocean.	Parts of California, Idaho, Nevada, Oregon, Utah, and Wyoming.	141,717 sq mi (367,050 km2)
17	Pacific Northwest	Water flows into the Strait of Georgia, Strait of Juan de Fuca, and the Pacific Ocean (in Oregon and Washington). It also includes part of the Great Basin in Oregon.	All of Washington and parts of California, Idaho, Montana, Nevada, Oregon, Utah, and Wyoming.	302,334 sq mi (783,040 km2)
18	California	Water flows into the Pacific Ocean within California, and also includes parts of the Great Basin in California where water stays within the basin.	Parts of California, Nevada, and Oregon.	168,579 sq mi (436,620 km2)
19	Alaska	All water drainage within the state of Alaska.	All of Alaska.	720,535 sq mi (1,866,180 km2)
20	Hawaii	All water drainage within the state of Hawaii.	All of Hawaii.	6,428 sq mi (16,650 km2)
21	Caribbean	Water drainage within Puerto Rico, the United States Virgin Islands, and other U.S. areas in the Caribbean.	Includes land areas where the United States has some interest or control.	3,582 sq mi (9,280 km2)
22	South Pacific	Water drainage within Guam, the Northern Mariana Islands, and American Samoa.		317,750 acres (1,285.9 km2)