Don River ecosystem

Category: Inland Aquatic Biomes.

Geographic Location: Eurasia.

Summary: The Don River, from antiquity considered the dividing line between Europe and Asia, is one of Russia's major rivers. The navigable river connects central Russia with the world's oceans.

The Don River rises in the Central Russian Upland, at an elevation of about 623 feet (190 meters) above sea level, and flows generally southward through European Russia and Ukraine for 1,161 miles (1,870 kilometers) before emptying into the Sea of Azov, a lobe of the Black Sea in southeastern Europe. The primary tributary of the Don is the Donets; other tributaries include the Kasivaya Mecha, Sosna, Cornaya Kalitva, Chir, Voronezh, Khopyor, Medvedits, Ilovlya, Sal, and Manych.

Hydrology and Climate

The Don is the third-largest river in the European section of the former Soviet Union, with a drainage area of about 262 square miles (680 square kilometers). It has no natural lakes, and is fed primarily by melted snow. The average rate of the Don is about 2.16 cubic miles (900 cubic meters) per second at its mouth, with considerable variation over the course of the year.

In general, water levels are highest in the spring and lowest in the autumn and winter; about 75 percent of the Don's flow occurs in March and April. The Tsimlyansk Reservoir, completed in 1953, was constructed to control the Don's annual flooding in its central section; it has an average depth of almost 32 feet (10 meters), and a maximum width of nearly 24 miles (40 kilometers).

The most important city on the Don is the port of Rostov-na-Donu, which lies about 29 miles (48 kilometers) from the mouth of the river. The Don has been a major trading channel since the time of the ancient Scythian nomadic peoples; it is navigable for approximately 851 miles (1,370 kilometers), and seagoing ships can use it up to Rostov-na-Donu. The river's transport function is enhanced by the Volga-Don Canal, completed in 1952, forming part of the Unified Deep Water System of Russia. As the Sea of Azov is connected to the Black Sea, and the Black Sea to the Mediterranean Sea, the Don is linked to all the world's oceans and is navigable for most of the year.

The upper Don flows along the eastern edge of the upland through a narrow valley with its right bank rising more than 295 feet (90 meters) above the river. This high right bank is a consistent feature of the river over most of its course. The Don drops little in elevation, just over 620 feet (about 190 meters), particularly during its upper course, resulting in slow water flow. The upper Don valley is located in the eastern European forest steppe, and is characterized by trees such as the oak, field maple, and ash. The river broadens south of Dankov, and at the town of Voronezh is joined by its first major tributary, the Voronezh River.

Below the town of Liski, the Don runs through a trough between the Kalach uplands and the hills of Belogorye, with an extensive floodplain on the left bank and the high right bank persisting. The Don makes a sharp bend below Medveditsa and broadens. In this region, it is joined by the Donets, the river's chief tributary, about 93 miles (150 kilometers) from Rostov, and by another tributary, the Manych. The lower Don basin is part of the grassland plains, or steppes, called the Pontic-Caspian steppe. It is characterized by shrublands, meadows, and riparian forests. The Don connects with the Black Sea through a series of bays and seas, beginning with the Gulf of Taganrog in the northeastern corner of the Sea of Azov, which in turn is connected to the Black Sea through the Kerch Strait.

The climate of the Don basin is continental, with annual precipitation ranging from 23 inches (584 millimeters) in the north to 15 inches (380 millimeters) in the south; average temperatures are in the range of 66–72 degrees F (19–22 degrees C) in July, and 12–18 degrees F (minus 11 to minus 8 degrees C) in January. The upper region of the Don freezes for an average of 140 days annually, while near Rostov it freezes for an average of 90 days per year. Increased use of the Don for irrigation has resulted in reduced flow, which was estimated in 1975 already to be 20 percent below 1950 levels. Strong offshore winds at the mouth of the Don also can reduce the water level in the river's lower reaches. Reduced water flow due to intense irrigation has increased the salinity of the Sea of Azov from 10–12 percent to 13–14 percent in the 1970s, which diminished fish catches and biological productivity; salinity in the Sea of Azov has since experienced incremental decline.

Biota and Human Impacts

The variety of animal and plants species are diverse. Mammals include the Asiatic black bear, brown bear, Siberian tiger, Amur leopard, lynx, wolf, wild boar, roe deer, and moose. Sturgeon, salmon, sea trout, and herring are fairly common in the river proper. Steller's sea eagle is among the raptors patrolling the skies.

The Volga-Don Canal has a length of just over 60 miles (100 kilometers) and includes multiple locks as well as pumps to maintain the water level. It was completed in the mid-20th century (although attempts to create such a canal date back to at least the 16th century) and began operation in 1952. The city of Rostov-na-Donu, located on the Don near the Sea of Azov, is the capital of the Rostov region and a major industrial and trading area. A canal has been dredged from this point to take ships through the Don delta; the city of Azov (formerly Tanais) lies at the southern end of the Don delta.

The size of the Don River means the environmental impact of the waterway changes as it flows. The middle basin area is dotted with mines, leaving mine waste in its wake, including sulfides as well as metals (arsenic, iron, copper, lead, manganese, cadmium, chromium, zinc, nickel, mercury) that occur naturally in the ore body and leave toxins, which accumulate in plants and animals. The polluted waters, which affect life along the banks, are being addressed by local nongovernment organizations such as Clean Water Foundation, Green World, Youth for Environment, and volunteers. Other efforts include the establishment of the non-governmental organization, the Centre for Ecologic Adversity Counteraction (CEAC), which promotes its agenda with media and educational campaigns.

Effects of global warming on the Don River biome are likely to include an acceleration of the already-documented trend toward drying of semiarid lands in the region. This, in turn, is projected to exacerbate the problem of dust storms and wind-driven erosion of ecological assets including riverbank structure, unforested hillsides, and agricultural lands. Additionally, the resultant dust storms could create higher turbidity and sedimentation within the river and its marshlands, to the detriment of established natural communities there. Forested areas of the biome are anticipated to undergo dominant-species migration, possibly with scattered islands of intrusive tree species linking up and overtaking the major stands of today's dominant trees. This will precipitate or accelerate the habitat pressures on the fauna that depend on such flora communities.

Bibliography

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

Lebedeva, E. A. “Waders in Agricultural Habitats of European Russia.” International Wader Studies 10, no. 1 (1998).

Levich, A. P., E. A. Zaburdaeva, V. N. Maksimov, N. G. Bulgakov, and S. V. Mamikhin. “The Search for Target Values of Quality Indices for Bioindicators of the Ecological State and Environmental Factors: Case Study of Water Bodies of the Don River.” Water Resources 36, no. 6 (2009).

Ruchin, Alexander, et.al. "Occurrence of the Amphibians in the Volga, Don River Basins and Adjacent Territories: (Russia): Research in 1996-2020." Biodiversity Data Journal, 29 Dec. 2020, doi.org/10.3897/BDJ.8.e61378. Accessed 1 Aug. 2022.