Ohio River

• Category: Inland Aquatic Biomes.
• Geographic Location: North America.
• Summary: A major river in the United States and a key tributary of the Mississippi River, the Ohio and its basin are home to tens of millions of people in several different ecosystems.

A long, shallow, often wide, and heavily interconnected river in the eastern United States, the Ohio River is the main tributary of the Mississippi River, flowing through a region of varying climates and ecosystems. It has been a significant transportation route from before European settlements, for Native Americans, through today. The Ohio River flows southwest almost 1,000 miles (1,600 kilometers) through six states: Pennsylvania, Ohio, West Virginia, Kentucky, Indiana, and Illinois. Along the way, it serves as the characteristically wiggling border for several of these states, including the southern borders of Illinois, Indiana, and Ohio; and parts of the northern borders of Kentucky and West Virginia. The entire watershed of the Ohio River extends even further, including parts of New York, Maryland, Virginia, North Carolina, Georgia, Tennessee, Alabama, and Mississippi.

Hydrology and Climate

The source of the Ohio is the Allegheny River in western Pennsylvania. In Pittsburgh, Pennsylvania, the confluence of the Allegheny and Monongahela Rivers form the beginning of the Ohio, earning this area the nickname Three Rivers. Near Cairo, Illinois, the Ohio enters the Mississippi River. At this point, there is usually more water coming from the Ohio than from the northern section of the Mississippi, helping to make the Ohio the main tributary of the Mississippi.

The river is often very wide, stretching as far as one mile across near Louisville, Kentucky. It is not, however, naturally deep, but locks and dams have greatly increased depth,up to about 170 feet (52 meters) near Louisville.

Because it travels so far, helping to divide the Northeast, Midwest, and Southern regions of the United States, the Ohio River is a part of several different climates. In its northern regions, especially eastern Ohio, northern West Virginia, and Pennsylvania, the weather is typical of areas with a humid continental climate. Similar to that of much of the Northeast, it features warm summers and cold winters, including frequent snow. The Allegheny River, and sometimes the Ohio around Pittsburgh, have been known to freeze in the winter, although this is becoming less common due to climate change.

Below Pittsburgh, the Ohio rarely freezes, and by western Kentucky it is always free of ice. In these areas, the weather is more similar to the upper South and characteristic of a humid subtropical climate, with hot summers, moderate winters, and only occasional snow.

The two uniting features about the climate of the Ohio River are relatively frequent rainfall, which helps to keep the river’s volume high, and relatively high humidity, especially in the summer. Because of this relatively frequent rainfall and low overall depth, flooding is common on the Ohio River. In particular, at least four severe floods occurred in recorded history, with waters rising in some cases to over 60 feet (18 meters), and more than doubling local flooding heights. One of the worst recorded floods was in 1937 when torrential rain caused the river to flood. The national weather service records over 350 people died during the flood and more than 1 million people were left homeless. The 1937 event held the record for the worst flood in Ohio's history, until the 2011 flood.

Flora and Fauna

The Ohio is home to a variety of ecosystems and species. Two major factors influence this. The first is the large variation in climate, described above. The second is the mixture of glacial and nonglacial soils around the river. Because large glaciers covered the region to the north of the Ohio River tens of thousands of years ago, but did not extend to the areas south of the river, the soils contain different mixtures of rocks and minerals, and are suitable for different types of plants.

The northern portions of the river ecosystem are known as mixed mesophytic and western mesophytic forests, meaning they are temperate, diverse, largely deciduous forests. Common trees include several species of hickory and oak, river birch, basswood, poplar, some eastern cottonwood, and the famous yellow buckeye, from which Ohio get its nickname, The Buckeye State.

Toward Illinois, Indiana, and western Kentucky, the banks of the river once included large bottomland hardwood forests. Many have been cut down, but some still remain, and others are growing back on abandoned farmland. Throughout the system, but particularly in the southern portions, many trees are well adapted to the river’s flooding. Species common here include bald cypress, tupelo gum, and more isolated patches of oaks and hickories than in the northern portions.

Especially in its southern reaches, the river is home to several species of large fish, including paddlefish and catfish. In total, over 150 types of fish call the river home. Although rare, bull sharks have even been found in the Ohio River as far north as Indiana. The river is also known for containing more than 50 different species of mussels. In part because of its fish, and because much of the river supports the dense hardwood and mesophytic forests nearby, many birds, including migrating birds, make use of the river. These include warblers (notably the prothonotary warbler and cerulean warbler), wrens, sparrows, and other small birds. Larger birds include the bald eagle, snow goose, and mute swan.

Many types of butterflies also take advantage of the flowers growing near the banks of the river, including hairstreaks, swallowtails, the tiny falcate orangetip, gemmed satyr, and monarch. Other typical insects here include praying mantis, solider beetles, diving beetles, tulip scale insects (which feed on tulip poplars), mayflies, carpenter ants, and cicadas.

Typical river amphibians in and near the Ohio and its tributaries include multiple types of salamanders, spring peepers, cricket frogs, Fowler’s toad, fence lizard, box and snapping turtles, and several types of garter snakes and milksnakes. Water snakes, such as the copperbelly, may live in tributaries that are slower moving than the Ohio.

Common mammals in and around the river include the river otter, white-tailed deer, rats, raccoons, squirrels, muskrat, mink, beavers, and bats. Bear, bobcat, and mountain lion still inhabit some forested areas surrounding the river.

A number of the plants and animals that live in or near the river are endangered. Pollution and other human impacts have killed more than 30 types of mussels formerly found in the river. At least three are completely extinct. Fish are still plentiful, but significant restrictions have been placed on eating Ohio River fish, due to contamination. Catfish and carp consumption, for example, is generally prohibited. Other endangered species include turtles, snakes, dragonflies, and reedgrass. Many small islands exist throughout the river, and these have often served as havens for small mammals, birds, amphibians, insects, and reptiles, even when surrounding lands along the shores were degraded.

Several invasive, alien species have been accidentally introduced by people to the river ecosystems, and are competing with and sometimes leading to the death of native species. Zebra mussels are one such pest, causing the decline of other types of mussels, and the animals that depend on them. Several kinds of Asian carp are also present in the river, where they compete for the same food with other, native fish.

Human Impact

According to a 2020 estimate from the US military, roughly 8 percent of the population of the United States, or over 25 million people, lived in the Ohio River’s basin that year, with the river itself serving as the source of drinking water for more than 3 million people. Although the river was no longer the largest source of transportation in the region, it was still a significant source of recreation such as boating and fishing. Some types of river freight traffic still made frequent use of the Ohio. The economic health of Ohio River cities depended, in part, on the value citizens placed on having attractive views and easy access to the river.

In the twenty-first century, invasive species, pollution from mine and agriculture runoff, and flooding in certain areas threaten both the people and other species that depend on the river. Although much progress has been made since the late twentieth century to reduce pollution, heavy storms also cause city sewer systems to overflow into the river, poisoning it in some places and requiring expensive water treatment facilities in others. The 20 dams still in operation on the river have helped to control its flow, but also allow silt and mud to pile up, reducing water visibility, river appearance, and bottom-dwelling animals.

Of particular concern is the river's high level of mercury pollution, which increased more than 40 percent between 2007 and 2013 according to Environmental Protection Agency (EPA) data released in 2015. The mercury level has led to health advisories regarding consuming fish caught in the river. In the 2015 report, the EPA stated that the Ohio River was the most polluted river in the country, citing the 24,180,821 pounds of industrial waste discharged into the river in 2013. A 2020 study by the Ohio River Valley Water Sanitation Commission estimated that 25,000 pounds of mercury had been released into the atmosophe around the river during their one year study period. That mercury eventually settles on land and is deposited into the Ohio River basin. The Ohio River Valley Water Sanitation Commission (ORSANCO), made up of representatives from the six states through which the river flows as well as from New York and Virginia, has historically set standards regarding industrial pollution for the river as a whole, but began passing off some responsibilities to the individual states in 2015 and in 2018 announced that most ORSANCO members were in favor of ending its role in setting pollution standards entirely, believing that EPA standards were sufficient to ensure a consistent level of pollution control across the six states. The Sierra Club and Ohio Valley Environmental Coalition filed a lawsuit in 2019 against the only chlor-alkali plant in the nation that continued to use liquid mercury to produce chlorine, potassium hydroxide, and sodium hydroxide using a process developed in the nineteenth century. While other plants had long switched to a technology developed in the 1960s that is less likely to pollute the water with mercury, this West Virginia facility had not done so by 2020 and was classified as the second-highest point polluter in the watershed of the Ohio River at that time. In November 2020 the lawsuit ended in a settlement which required the West Virginia plant to reduce its mercury pollution and help fund Ohio River conservation efforts.

Concerns over pollution in the Ohio River were renewed in early 2023 after a devastating train derailment on February 3, 2023, in East Palestine, Ohio, led to the spill of a large number of toxic chemicals, including vinyl chloride, a known carcinogen. The spill and subsequent chemical fires forced the evacuation of many nearby residents and by the end of February had caused the deaths of over 40,000 marine animals in a five-mile radius, including fish, amphibians, and other creatures. While water officials conducted an investigation and determined that the local water supply was safe to drink in the wake of the disaster and did not contain dangerous levels of pollutants, a number of residents and environmental activists remained concerned about possible contamination from chemicals traveling downstream from the accident site into the Ohio River itself. Some communities downstream of the accident, including Huntington, West Virginia, temporarily switched to alternate water supplies over fears of contamination in the Ohio River.

Although climate change appeared to have had some effects on the river basin by the first decades of the twenty-first century, the scarcity of research on the impact of climate change on the Ohio River made it difficult to assess what changes had occurred. Any future changes in the Ohio River water flow may impact human health, agriculture, water supplies, property and infrastructure, as well as tourism and recreation. Government and civic efforts continue today to focus on reducing these impacts, while maintaining desirable recreational and commercial use of the Ohio River.

Bibliography

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Bruggers, James. "Ohio River Tops Nation for Industrial Pollution." Courier-Journal [Louisville], 11 Mar. 2015, www.courier-journal.com/story/tech/science/environment/2015/03/11/ohio-river-panel-ease-mercury-requirements/70153174/. Accessed 11 Oct. 2024.

Feldkamp, Bonnie Jean. "We Mapped the Toxic Wastewater Discharges along the Ohio River. Here's What We Learned." Allegheny Front, 15 Jan. 2020, www.alleghenyfront.org/we-mapped-the-toxic-wastewater-discharges-along-the-ohio-river-heres-what-we-learned/. Accessed 11 Oct. 2024.

Griffin, Connor. "As Pollution from Ohio Train Wreck Heads Downstream, Water Utilities Assure Safety." St. Louis Post-Dispatch, 19 Feb. 2023, www.stltoday.com/news/local/state-and-regional/as-pollution-from-ohio-train-wreck-heads-downstream-water-utilities-assure-safety/article‗21441c23-3eef-5487-9217-08f66dccff3b.html. Accessed 11 Oct. 2024.

Jackson, Tom. The Ohio River (Rivers of North America). Gareth Stevens Publishing, 2003.

“1937 Ohio River Record Flood.” National Weather Services, www.weather.gov/iln/1937ohioriverflood. Accessed 11 Oct. 2024.

“Ohio River Basin Mercury Loading Analysis.”  Ohio River Valley Water Sanitation Commission, Jun. 2020, www.orsanco.org/wp-content/uploads/2020/06/MercuryLoadingAnalysisReportFinalJune2020.pdf. Accessed 11 Oct. 2024.

"Ohio River Pollution: Group That Monitors River's Health May Drop Standards." Cincinnati.com, 28 Feb. 2018, www.cincinnati.com/story/news/politics/2018/02/28/ohio-river-pollution-group-monitors-rivers-health-may-drop-standards/380532002/. Accessed 11 Oct. 2024.

Pearce, John Ed and Richard Nugent. The Ohio River. UP of Kentucky, 1989.

Schulte, Jerry G. “The Implications of Climate Change on the Ohio River and the Ohio River Valley Water Sanitation Commission.” American Water Resource Association, vol. 1, 2009.

Willis, Pablo. "Settlement Requires WV Chemical Plant to Limit Mercury Pollution & Pay for Ohio River Conservation Efforts." Sierra Club, 30 Nov. 2020, www.sierraclub.org/press-releases/2020/12/settlement-requires-wv-chemical-plant-limit-mercury-pollution-pay-for-ohio. Accessed 11 Oct. 2024.