What is a Watershed
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A watershed is all of the land that drains into the same location. Watersheds come in all shapes and sizes. They cross county, state, and national boundaries. In the continental US, there are 2,110 watersheds; including Hawaii, Alaska, and Puerto Rico, there are 2,267 watersheds.
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Geographical Features
The watershed drainage area of the Ohio River Watershed, excluding the Tennessee River Basin, includes parts of Illinois, Indiana, Kentucky, Maryland, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia. The total drainage area for the Ohio River Watershed is 203,940 square miles. The total area of the Ohio River Watershed covered by the Mid-Atlantic States of Pennsylvania, Maryland, Virginia and West Virginia is 43,405 square miles.
About the Ohio River Watershed
Most of the Ohio River Watershed is drained by tributaries; less than five percent of the basin runoff drains directly into the main stem. The runoff characteristics of the tributaries, therefore, determine the quantity of flow in the Ohio at any time.
Two main tributaries, the Allegheny and the Monongahela, located in the Middle Atlantic Region form the beginning of the Ohio River at Pittsburgh. Located on the Allegheny Plateau, the Allegheny Watershed crosses Pennsylvania and New York and covers 11,770 square miles of drainage area. Within the Watershed are 13 sub watersheds (eg. French Creek, Clarion, Kiskimenetas-Conemaugh) and numerous sub-sub watersheds. The watershed covers 22 counties and has 325 miles of main stem. Located within the watershed are the Allegheny Mountains extending west from the Appalachian Mountains. The headwaters of the Allegheny River are located in upland forested areas and the terrain of the watershed remains a mixture of mountains and plateaus throughout the watershed. The formation of the Ohio River at the confluence of the Allegheny and the Monongahela Rivers is known locally as the Three Rivers area. The total drainage area for the Ohio River Watershed is 203,940 square miles.
The area covered by the Monongahela River Watershed is one of the most industrialized areas in the country and includes the coal fields of West Virginia and Western Pennsylvania. The watershed flows through 7,400 square miles of drainage land in three states, with the main stem extending more than 128 miles. There are six sub watersheds that cover the states of Pennsylvania, West Virginia and Maryland, two of which are the Cheat River and Youghioghey River watersheds. The Monongahela River watershed also includes 85 miles designated as a National Wild and Scenic River and the Cheat River is located within the Monongahela National Forest.
Two main tributaries, the Allegheny and the Monongahela, located in the Middle Atlantic Region form the beginning of the Ohio River at Pittsburgh. Located on the Allegheny Plateau, the Allegheny Watershed crosses Pennsylvania and New York and covers 11,770 square miles of drainage area. Within the Watershed are 13 sub watersheds (eg. French Creek, Clarion, Kiskimenetas-Conemaugh) and numerous sub-sub watersheds. The watershed covers 22 counties and has 325 miles of main stem. Located within the watershed are the Allegheny Mountains extending west from the Appalachian Mountains. The headwaters of the Allegheny River are located in upland forested areas and the terrain of the watershed remains a mixture of mountains and plateaus throughout the watershed. The formation of the Ohio River at the confluence of the Allegheny and the Monongahela Rivers is known locally as the Three Rivers area. The total drainage area for the Ohio River Watershed is 203,940 square miles.
The area covered by the Monongahela River Watershed is one of the most industrialized areas in the country and includes the coal fields of West Virginia and Western Pennsylvania. The watershed flows through 7,400 square miles of drainage land in three states, with the main stem extending more than 128 miles. There are six sub watersheds that cover the states of Pennsylvania, West Virginia and Maryland, two of which are the Cheat River and Youghioghey River watersheds. The Monongahela River watershed also includes 85 miles designated as a National Wild and Scenic River and the Cheat River is located within the Monongahela National Forest.
Ohio River Watershed Facts
- The Ohio River is 981 miles (1582 km) long, starting at the confluence of the Allegheny and the Monongahela Rivers in Pittsburgh, Pennsylvania, and ending in Cairo, Illinois, where it flows into the Mississippi River.
- The Ohio River flows through or borders six states: Illinois, Indiana, Kentucky, Ohio, Pennsylvania, and West Virginia.
- The Ohio River is a source of drinking water for more than three million people.
- More than 25 million people, almost 10 percent of the U.S. population, live in the Ohio River Watershed.
- Approximately 150 species of fish have been collected from the Ohio River.
- The average depth of the Ohio River is approximately 24 feet.
- The widest point along the Ohio River is approximately 1 mile at the Smithland Dam.
- There are 20 dams and 49 power generating facilities on the Ohio River. For hydropower impacts, click here: Hydropower Impacts. The power generating facilities have a combined capacity in excess of six percent of the total US generating capacity. The navigation dams provide a nine-foot minimum depth for commercial navigation.
- Over 230 million tons of cargo are transported on the Ohio River each year. Coal and other energy products make up approximately 70 percent of the commerce traveling by barge.
