# Ohio water resource region

The Ohio water resource region is one of 21 major geographic areas, or regions, in the first level of classification used by the United States Geological Survey to divide and sub-divide the United States into successively smaller hydrologic units. These geographic areas contain either the drainage area of a major river, or the combined drainage areas of a series of rivers.
The Ohio region, which is listed with a 2-digit hydrologic unit code (HUC) of 05, has an approximate size of 162,916 square miles (421,950 square kilometers), and consists of 14 subregions, which are listed with the 4-digit HUCs 0501 through 0514.
This region includes the drainage of the Ohio River Basin, excluding the Tennessee River Basin. Includes parts of Illinois, Indiana, Kentucky, Maryland, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia.

## List of water resource subregions

| Subregion HUC | Subregion Name | Subregion Description | Subregion Location | Subregion Size | Subregion Map |
| 0501 | Allegheny Subregion Subregion | The Allegheny River Basin. | Pennsylvania and New York. | 11,600 sq mi (30,000 km$^2$) | HUC0501 |
| 0502 | Monongahela Subregion Subregion | The Monongahela River Basin. | Maryland, Pennsylvania, and West Virginia. | 7,310 sq mi (18,900 km$^2$) | HUC0502 |
| 0503 | Upper Ohio Subregion Subregion | The Ohio River Basin below the confluence of the Allegheny and Monongahela River Basins to the confluence with the Kanawha River Basin, excluding the Muskingum River Basin. | Ohio, Pennsylvania, and West Virginia. | 13,200 sq mi (34,000 km$^2$) | HUC0503 |
| 0504 | Muskingum Subregion Subregion | The Muskingum River Basin. | Ohio | 7,980 sq mi (20,700 km$^2$) | HUC0504 |
| 0505 | Kanawha Subregion Subregion | The Kanawha River Basin. | North Carolina, Virginia, and West Virginia. | 12,200 sq mi (32,000 km$^2$) | HUC0505 |
| 0506 | Scioto Subregion Subregion | The Scioto River Basin. | Ohio | 6,440 sq mi (16,700 km$^2$) | HUC0506 |
| 0507 | Big Sandy–Guyandotte Subregion Subregion | The Big Sandy and Guyandotte River Basins. | Kentucky, Virginia, and West Virginia. | 5,900 sq mi (15,000 km$^2$) | HUC0507 |
| 0508 | Great Miami Subregion Subregion | The Great Miami River Basin. | Indiana and Ohio. | 5,330 sq mi (13,800 km$^2$) | HUC0508 |
| 0509 | Middle Ohio Subregion Subregion | The Ohio River Basin below the confluence with the Kanawha River Basin to the confluence with the Kentucky River Basin, excluding the Big Sandy, Great Miami, Guyandotte, Kentucky, Licking and Scioto River Basins. | Indiana, Kentucky, Ohio, and West Virginia. | 8,850 sq mi (22,900 km$^2$) | HUC0509 |
| 0510 | Kentucky–Licking Subregion Subregion | The Licking and Kentucky River Basins. | Kentucky | 10,500 sq mi (27,000 km$^2$) | HUC0510 |
| 0511 | Green Subregion Subregion | The Green River Basin. | Kentucky and Tennessee. | 9,140 sq mi (23,700 km$^2$) | HUC0511 |
| 0512 | Wabash Subregion Subregion | The Wabash River Basin. | Illinois, Indiana, and Ohio. | 32,600 sq mi (84,000 km$^2$) | HUC0512 |
| 0513 | Cumberland Subregion Subregion | The Cumberland River Basin. | Kentucky and Tennessee. | 17,700 sq mi (46,000 km$^2$) | HUC0513 |
| 0514 | Lower Ohio Subregion Subregion | The Ohio River Basin below the confluence with the Kentucky River Basin, to the confluence with the Mississippi River, excluding the Cumberland, Green, Tennessee, and Wabash River Basins. | Illinois, Indiana, and Kentucky. | 12,500 sq mi (32,000 km$^2$) | HUC0514 |