Dnieper River Ecosystem

• Category: Inland Aquatic Biomes.
• Geographic Location: Eastern Europe.
• Summary: The Dnieper River is Europe's fourth-longest river, the main freshwater source in Ukraine, and a key feeder of the Black Sea.

Originating in the Valdai Hills, approximately 93 miles (150 kilometers) northeast of Smolensk, Russia, the Dnieper River travels generally southward for more than 1,422 miles (2,290 kilometers) before releasing its waters into the Black Sea. The Dnieper River watershed lies in three Eastern European countries: Russia, Belarus, and Ukraine. Considered the fourth-longest river in Europe, and draining an area of 196,526 square miles (509,000 square kilometers), the river system is known for the dams and reservoirs that provide energy, industrial development, and irrigation water to urban and agrarian populations of Eastern Europe.

However, the increase in large-scale industrial activities has come at a steep price for this hydrologic system, as pollution concentrations and unsustainable resource-use levels have degraded the waters of the Dnieper. This, in turn, has resulted in deleterious impacts on the entire riparian ecosystem and on the Black Sea.

Climate and Hydrology

Dominated by a moderate temperate continental climate, temperature and precipitation vary from north to south along the Dnieper riparian system. Temperatures upstream are more affected by this continental system, whereas, at the delta and mouth of the river, the climate is moderated by the inland Black Sea. On average, temperatures are cold in the winter, with average December through January temperatures of 27 degrees F (minus three degrees C), and trend from warm to very warm in the summer. The average July temperature is 75 degrees F (24 degrees C).

Precipitation is variable, but predominantly arrives as rain in the summer and fall. A moderate amount of snow collects in the lower portion of the region in the winter; in the upper reaches, the winter is long and areas of the river may freeze. The mean annual precipitation in the upper Dnieper basin is approximately 28 inches (71 centimeters).

The Dnieper River hydrology has been documented for more than 250 years. Spring snowmelt in the upper basin area historically provided a pulse of freshwater for higher flows. Approximately 60 percent of the annual runoff arrives in March through May. The confluence of many large tributaries, such as the Inhulets, Sozh, Berezina, Ros, Sula, and the Pripyat Rivers, contributes to the seasonal input. Along the route, the river channel narrows and widens from 131 feet (40 meters) to over 1,968 feet (600 meters). The annual average discharge is around 2,184 cubic yards (1,670 cubic meters) per second, and carries large quantities of dissolved sediment into the Black Sea.

The river was once known for the zones of rapids that made it difficult to navigate. The rapids in the upper reach cut through limestone cliffs; the famous Dnieper rapids in the middle region were situated above Zaporizhzhya. However, the rapids and the natural flow of the Dnieper have long been altered by hydroelectric dams and reservoir construction. This affects the natural flow rate and peak discharge times, which now accommodate irrigation and energy production.

Geography and Plant Types

The Dnieper River is a meandering river system, which typically has a sinuous stream channel moving through alluvial (stream-deposited) sediments, turning and twisting over fairly low elevation gradients. Characteristic of many long river systems, the Dnieper has many tributaries and is divided into three reaches: the upper, middle, and lower Dnieper. The upper reaches of the river, from the source in central Russia to north of the Ukrainian city of Kiev, starts at an elevation of 722 feet (220 meters) and gradually descends through swampy and forested terrain. The watershed here descends and carries itself through the gently sloping uplands of Russia and Belarus. Forests of willow and alder with lush meadows and marshes dominate the banks of the upper riparian ecosystem. This section is the most heavily forested of the three Dnieper regions, with as much as one-fourth of the watershed covered in forests; it is also the region with the greatest extent of swamp vegetation.

The middle portion, from the environs of Kiev to Zaporizhzhya, Ukraine, and the lower Dnieper, from Zaporizhzhya to the Black Sea, flow through Belarus and Ukraine. These two longer reaches have the most sinuosity and a predominance of features known as oxbow lakes and meander scars. Oxbow lakes are created when curves of the main river are cut off, resulting in crescent-shaped lakes. Meander scars are fertile, sediment-filled pockets along the floodplain of a river, created after the main channel of the river moves.

In the center of the basin here, an ecotone (boundary between two ecological regions) is established between the moist forests and the arid steppe. The lower reaches of the basin broadens out throughout Ukraine and moves through the arid steppe, winding its way through swampy marshes, with reeds and sand-bar islands.

The lower Dnieper passes through more arid lands, in the form of the steppe country of the Black Sea Depression, a lowlands area of natural terraces cut by shallow rivers and also characterized by marshy seasonal floodplains. Here, too, the Oleshia Sands is found, formed by sedimentary deposits when the mouth of the Dnieper was situated here, well north of the present-day delta. Sparse native vegetation has been supplanted in many cases here by irrigated cultivation of crops such as grapevines and fruit trees. The Dnieper Delta carries four main streams; broad floodplains separate these shallow brackish flows, known collectively as the Dnieper-Boh Estuary, as they enter the Black Sea.

Biota and Environmental Concerns

The lower reach of the Dnieper provides irrigation water to the well-known black soils (chernozems) of the Ukraine where wheat, corn, rice, and other agricultural commodities are grown. Fishing in the Dnieper is both a recreational and commercial activity, with more than 60 species of fish living in the waters. Commercially important species include pike, catfish, barbel, perch, common bream, vimba, roach, and ruff.

However, the Dnieper has lost many of the anadromous fish species—such as sturgeon and shad—that once prospered here, in the wake of its segmentation by aggressive dam construction in the 20th century. Characteristic fish today include the Black Sea goby (Romanogobio belingi), the beardless tadpole goby (Benthophiloides brauneri), and the estuarine perch (Sander marinus).

More than 120 species of mollusks—at least 50 in class Bivalvia and 70 in class Gastropoda—are known in the Dnieper River biome, many vital to the aquatic food chain here. This breadth of species includes the zebra mussel (Dreissenapolymorpha), widely known around the world as an invasive freshwater species, but native to the Dnieper region. Other thriving mollusks here include the swollen river mussel (Unio tumidus) and the sand gaper (Mya arenaria).

Among avian species of the Dnieper River biome are great snipe (Gallinago media), curlew (Numenius arquata), marsh sandpiper (Tringa stagnalis), lapwing (Vanellus vanellus), and redshank (Tringa totanus).

One of the most polluted waterways in a fairly densely populated region of the former Soviet Union, the Dnieper had long been inundated with industrial, agricultural, and municipal runoff. The effects of such sources were trumped in 1986 with the core meltdown of the Chernobyl Nuclear Power plant, located on the Dnieper's tributary, the Pripyat, upstream of Kiev. Wind conditions during the disaster actually favored much of the Dnieper watershed, as radioactive contaminants were generally swept away to the northwest. Still, the immediate release and bioaccumulation of radioactive fallout materials into the Dnieper riparian ecosystem has had a large impact on the fishing, irrigation, and drinking water of the middle and lower reach of the river. Remediation efforts have had some positive impact, as have increased ecological advocacy within the post-Soviet era.

These efforts on behalf of the Dnieper continue to be balanced against the climactic impact of warming temperatures, which can increase rainfall that could lead to more frequent flooding overall and to flash floods during rainy periods. On the other hand, the warmer temperatures would likely expand the farming areas for winter wheat, the largest crop in Ukraine, as well as other crops like barley and potatoes—but also require more irrigation to compensate for the periodically decreased rainfall. The increased temperatures could also drive in insects not usually seen in this temperate climate.

Russia-Ukraine War

The Dnieper River became strategically important when Russia invaded Ukraine in February 2022. The river essentially divides Ukraine in half and became a key link to sending supplies from one side of the country to the other. To create obstacles for Russia, the Ukrainian army used missiles to destroy a bridge over the Dnieper River that the Russians were using the transport supplies and reinforcement need by their military. Complicating matters more, the Kakhovka dam on the river was destroyed in June of 2023. While each side blamed the other, scientists warn that the destruction of the dam has grave environmental consequences. A year after the dam's destruction, researchers found extensive damage, including the flooding of nature reserves and the deaths of countless organisms near the confluence of the Dnieper and the Black Sea. On the lakebed of the river are billions of rotting mussels. Scientists fear the ecological and environmental costs resulting from the war.  

Bibliography

Alexandrov, Boris, et al. "Trends of Aquatic Alien Species Invasions in Ukraine." Aquatic Invasions, vol. 2, no. 3, 2007, pp. 215-42.

Blinnikov, Mikhail S. A Geography of Russia and Its Neighbors. Guilford Press, 2011.

Kovalssky, V., and G. M. Henebry. "Change and Persistence in Land Surface Phenologies of the Don and Dnieper River Basins." Environmental Research Letters, vol. 4, no. 6, 2009, pp. 45-62.

Onishi, Y., et al. "Aquatic Assessment of the Chernobyl Nuclear Accident and Its Remediation." Journal of Environmental Engineering, vol. 133, no. 11, 2001, pp. 1015-23.

Schwirtz, Michael. "'We Need to Oppose Russia': Ukrainians Find Common Purpose." The New York Times, 14 Feb. 2022, www.nytimes.com/2022/02/14/world/europe/ukraine-russia-invasion-identity.html. Accessed 4 Nov. 2024.

Stone, Richard. "Laid to Waste." Science, vol. 383, no. 6678, 5 Jan. 2024, www.science.org/content/article/ukrainian-scientists-tally-grave-environmental-consequences-kakhovka-dam-disaster. Accessed 4 Nov. 2024.