Rivers

Rivers. (Map: Rivers of Ukraine.) Courses of flowing water in well-defined channels, usually growing in volume between the source and the point of entry into a sea, a lake, or another river. Streams or rivulets are smaller, with the volumes involved not being closely defined.

The rivers of Ukraine generally flow southward into the Black Sea or the Sea of Azov. The notable exceptions are in the northwest, where the prevalent flow is northward into the Prypiat River, a tributary of the Dnipro River, or into the Vistula River (Wisła River), which flows through Poland into the Baltic Sea. Nevertheless over 90 percent of the territory of Ukraine is situated in the Black Sea–Sea of Azov drainage basin. That area is drained by major rivers, such as the Tysa River, the Prut River, and the Seret (Siret) River, by way of the Danube River; the Dnister River, the Boh River, and the Dnipro River, together with its major tributaries, the Prypiat and the Desna River; the Don River with the Donets River and its tributary, the Oskil River (Oskol River in Russian); and the Kuban River. The remaining Ukrainian territory belongs to the Baltic Sea drainage basin, which incorporates the right-bank tributaries of the Vistula, the Buh, the Vepr River, and the Sian River. With the exception of the Carpathian Mountains, the divides between the Black Sea and the Baltic Sea drainage basins and between the major river basins usually follow low elevations. That allows the rivers of various drainage basins to be connected with canals for river-barge navigation between the Baltic and the Black seas.

There are approx 30,000 rivers crossing Ukrainian ethnographic territory. Of that number about 23,000 are in Ukraine. With a combined length of nearly 180,000 km, most are small; in Ukraine there are 117 rivers the watercourses of which exceed 100 km, but only 13 that are longer than 500 km (they are noted in table 1). The characteristics of rivers, such as the density of the river network as well as the volume and the seasonality of the flow, depend on factors such as climate, geology, relief, vegetation, and human modifications of the landscape.

River characteristics. River networks or drainage densities vary throughout Ukraine. They are highest in the mountainous regions, where the greatest annual precipitation occurs; there they attain nearly 1.1 km of watercourse per sq km of territory. Drainage densities decline to about 0.6 km/sq km in Subcarpathia, the Tysa Lowland, and Subcaucasia, and to 0.5 km/sq km in the uplands of Roztochia, Podilia, and the Donets Ridge, where porous limestone provides for better underground drainage. In general the river network becomes less dense to the south and east in keeping with the declining precipitation. Low drainage densities (less than 0.1 km/sq km) occur between the lower Desna and the upper reaches of the Oster River and between the Trubizh River and the Supii River. There are no rivers (except for a few seasonal intermittent streams) between the lower Dnipro River and the Molochna River.

Rivers are fed by rainfall, snowmelt, groundwater, and glaciers. In Ukraine rainfall accounts for nearly 75 percent of the total precipitation. The greater proportion of rainfall evaporates from the surface or infiltrates the soil, and only a small portion provides for surface runoff into the rivers (less than 10 percent in the plains, although it can reach up to 50 percent in the mountains). In the steppe zone nearly all the rainfall evaporates or seeps into the soil. The rivers of the plains are fed mainly by melting snow. Groundwater feeds rivers throughout the year. The mountain glaciers of the Caucasus Mountains provide water for the Kuban River and other rivers. In general the main source of water for the mountain rivers is rainfall. In the plains the rivers are fed mainly by snowmelt, 50–80 percent; groundwater contributes an additional 10–20 percent.

For Ukraine as a whole the mean annual surface runoff amounts to 14 percent of the atmospheric precipitation (in Ukraine representing approx 85 mm of river discharge of approx 600 mm). The mean annual surface runoff varies not only among the river basins (see table 1) but also within the river basins themselves, according to the hydrological conditions. The highest runoff (in liters per second per sq km or l/s/sq km) is 75 (2,340 mm) in the Caucasus Mountains, 35 (1,100 mm) in the Carpathian Mountains, and 15 (470 mm) in the Crimean Mountains. For the Ukrainian uplands and lowlands the mean annual surface runoff ranges from 1 to 4 l/s/sq km (30–130 mm). In the steppe it diminishes to a range of 0.5 to 1 l/s/sq km (16–30 mm). In the nonmountainous areas there is a gradient of decreasing runoff from north to south in keeping with precipitation. High anomalies occur on uplands, where higher precipitation and better drainage contribute to higher runoff. Low anomalies are found in the lowlands north of Lutsk and east of Kyiv, the former associated with karst (where porous limestone absorbs much of the precipitation), and the latter with bogs (where impeded drainage reduces runoff). In the mountains runoff increases with higher elevation.

Stream flow varies considerably from year to year. In dry years, for example, the large rivers of Ukraine discharge from three-quarters to less than one-half of their flow in normal years (see table 2). Over a monthly period greater variations occur. The Boh River, for example, with a mean March runoff of 20.7 mm, discharged only 3.6 mm in March 1921, but 81 mm in March 1922. Even greater variations are experienced by smaller streams.

Seasonal variation in the flow of rivers is considerable and is closely related to the amount of surface water available. Both the highest availability of surface water and the highest flows occur in the spring, when the snow melts. The spring flow accounts for 50–80 percent of the total annual discharge of the major rivers and for nearly all the annual discharge of the small, intermittent streams of the steppes. The lowest availability of surface water occurs in the winter, when only occasional thaws release snowmelt, and the lowest flows tend to occur during the warm, dry weather of the late summer and early fall, when the lowest quantities of water are available through both surface runoff and groundwater seepage. Spring floods or high flows in small streams last for 10 to 15 days, whereas large rivers may sustain high flows for 30 to 45 days. In addition to spring peak flows, summer floods associated with downpours are particularly common in the mountain streams of the Caucasus and Carpathian regions. The Kuban River hydrograph, however, reveals four seasonal high flows: two in the spring (in February, when the snow melts in the lower part of the drainage basin, and in April, when the snow melts in the mountains), one in the summer (through June and July, associated with the surface melting of the glaciers), and one in the fall (caused by increased precipitation in October). In the Tysa River Basin, winter floods are not uncommon; they are associated with the thaws triggered by the incursions of cyclonic storms from the Mediterranean.

Before the construction of the Kyiv Reservoir particularly large spring floods occurred in the Dnipro River north of Kyiv, where waters from snowmelt converged from both the Prypiat River and the Desna River. Spring floods in the broad, flat Prypiat floodplain occur regularly. Spring floods in the northward-flowing Sian River and Buh River and in the upper part of the Dnister River are caused by early and rapid melting of the snow in the upper part of the river basins, while the frozen middle stretches of the rivers overflow with ice jams. Near the mouths of the Dnipro River, the Danube River, the Boh River, and the Kuban River considerable flooding and fluctuation in water level occur in conjunction with the wind's pushing of seawater up against the windward shore (setup) or as a backwash following the offshore wind's withdrawing of it (seiche).

The winter regime of the rivers begins with the formation of ice on the surface. The freeze-up occurs earliest in the northeast (the upper Desna River Basin) at the end of November and progressively expands southward. Freeze-up along the Dnipro comes later; it reaches Kyiv by 21 December and Kherson by 28 December. The less voluminous Boh River experiences somewhat earlier freeze-ups, at Vinnytsia by 6 December and at Voznesenske by 11 December. The upper reaches of the Dnister River in Subcarpathia begin to freeze up in mid-December, but lower down near Zalishchyky the river does not freeze over until the end of December. Further east at Dubosari, freeze-up sets in by 20 December. The Kuban River and the Tysa River do not attain a stable ice cover, and the ice cover on the Sian River and the Buh River is often disrupted by thaws.

The breakup of ice in the spring begins in the south and advances northward. The mean dates for the Dnipro River are 3 March at Kherson, 15 March at Zaporizhia, and 24 March at Kyiv. For the Boh River they are 7 March at Voznesenske and 21 March at Vinnytsia. On the Dnister River ice begins to break up at Zalishchyky (4 March) before it does so at Dubosari (9 March), with ice jam flooding often the result. The problem is even more severe on the northward-flowing Sian River and Buh River. Mountain streams, which begin the break⌐up of ice from downstream, are spared the worst ice jam flooding. On average the rivers are ice-covered in northern Ukraine for nearly 3.5 months; in the south the ice cover lasts 2.5 months or less.

Rivers carry considerable material in suspension and solution, the quantity depending on the velocity of the current and the geology of the terrain. Mountain streams transport the largest quantity of suspended material, especially during floods, when they are capable of rolling stones and small boulders along their beds. Slow-flowing rivers in the lowlands carry the least material. Rivers almost always carry very small particles (mostly clay and silt) in suspension, which make the water appear muddy. The clearest rivers of Ukraine are found in Polisia, where small particles in suspension do not exceed 50 g/cu m; the muddiest are the mountain streams in flood and the full-fed tributaries of the middle stretch of the Dnister River, which may carry up to 1,000 g/cu m. In other rivers the concentration of particles in suspension generally varies from 150 to 500 g/cu m.

The concentration of dissolved minerals in river waters of northern Ukraine varies from 200 to 500 mg/l. That concentration increases to the south and east, where there is an increasing presence of soluble minerals in sedimentary rocks and an increasing soil salinity; it attains the highest values (nearly 2,000 mg/l) in the Donets Basin and in rivers between the Danube River and the Dnister River. The lowest concentrations (below 100 mg/l) are found in the fast-flowing streams of the Carpathians.

Regional characteristics of rivers. Ukraine may be subdivided into 11 regions according to hydrological factors and the nature of the rivers: Polisia, the Volhynia-Kholm Upland, the Podolian Upland, the Dnipro Upland, the Dnipro Lowland, the Donets Ridge, the southwestern margin of the Central Upland, the Black Sea Lowland, the Crimean Mountains, the Carpathian Mountains and Subcarpathia, and the Western Caucasia and Subcaucasia. Polisia is drained by the Dnipro River (north of Kyiv), the Prypiat River, the Desna River, and the Buh River. The mean annual precipitation is 500–600 mm, and the mean annual runoff, 100–120 mm (20 percent). River gradients are gentle (about 0.5 m/km), and the river currents are slow. River valleys are wide, and their low and swampy banks are inundated each year by the spring floods. Ice covers the rivers, on average, 3.5 months, with longer duration in the east than the west.

The Volhynia-Kholm Upland is drained by the Vepr River, the Buh River, and the right-bank (southern) tributaries of the Prypiat River—the Stokhid River, the Styr River with its tributary, the Ikva River, and the Horyn River with its tributary, the Sluch River. The mean annual precipitation is 500–700 mm, and the mean annual runoff, 100–150 mm (20 percent). River gradients in the south exceed 1 m/km but decline to the north. River valleys are wide and frequently swampy and experience floods in the spring. The duration of the ice cover varies from 3 months in the west to 3.5 months in the east.

The Podolian Upland is drained by the left-bank (northern) tributaries of the Dnister River and the right-bank (western) tributaries of the Boh River. The mean annual precipitation declines from 700 mm in the west to 450 mm in the southeast, and the range of the mean annual runoff is even greater, from 200 mm (30 percent) in the west to 40 mm (10 percent) in the southeast. The density of the river network varies from 0.4 to 0.5 km/sq km. In the upper reaches of the rivers the gradient is shallow (about 1 m/km), and the valleys are wide and swampy in places. In the middle reaches the gradient becomes steeper, and the river valleys become narrow and deep, most notably in the Dnister's middle reaches. In the southwestern extremity of the Ukrainian Crystalline Shield the riverbeds are stony. Spring floods are common, and the Dnister also experiences summer floods. The ice cover lasts about 3 months.

The Dnipro Upland is drained by the right-bank (western) tributaries of the Dnipro River (the Teteriv River, the Irpin River, the Ros River, the Tiasmyn River, and the upper Inhulets River) and the left-bank (eastern) tributaries of the Boh River (the Sob River, the Syniukha River, and the upper Inhul River). The mean annual precipitation is 450–550 mm, and the mean annual runoff diminishes from 100 mm (20 percent) in the northwest to 30 mm (6 percent) in the southeast. River gradients are approx 2 m/km. Rivers in the Ukrainian Crystalline Shield are stony and have rapids. The deep river valleys are canyonlike in their upper reaches. Floods occur in the spring. The ice cover lasts for three months, although the period is shorter by one to two weeks in the south.

The Dnipro Lowland is drained by the left-bank (eastern) tributaries of the Dnipro River: the Sula River, the Psol River, the Vorskla River, the Orel River, and the Samara River. The mean annual precipitation decreases from 550 mm in the north to 450 mm in the south, and the mean annual runoff declines from 120 mm (22 percent) to 40 mm (9 percent) in the same direction. Riverbeds are well graded, with a drop of 1 m/km. The river valleys are broad with gently sloping banks. High water levels occur in the spring. The ice cover period ranges from 3.5 months in the north to only 2 months in the south.

The Donets Ridge, bounded by the Donets River to the north, is drained by the right-bank (southwestern) tributaries of the Donets, the Miius River, and the Kalmiius River that flow into the Sea of Azov, and the upper reaches of two left-bank (eastern) tributaries of the Dnipro River, the Vovcha River and the Samara River. The mean annual precipitation is approx 500 mm, and the mean annual runoff, approx 50 mm (10 percent). The gradient of the Donets is only 0.5 m/km; the gradients of the other rivers are 1 m/km or more. The river valleys are deep, and the right bank of the Donets is considerably higher than the left bank. High water occurs in the spring, and the ice cover lasts about 3 months.

The southwestern margin of the Central Upland is drained by the upper reaches of the left-bank (eastern) tributaries of the Dnipro River (the Desna River with its tributary, the Seim River, the Psol River, and the Vorskla River), the upper reaches of the Donets River and its left-bank (eastern) tributaries (the Oskil River, the Aidar River, and the Derkul River), and the right-bank (western) tributaries of the Don River (notably the Chorna Kalytva River). The mean annual precipitation is 400–500 mm, with runoff decreasing from 120 mm (24 percent) in the north to 60 mm (15 percent) or less in the south. River gradients are approx 2 m/km. River valleys are deep, with the right banks higher than the left banks. Floods occur in the spring, and the ice cover lasts about 3.5 months.

The Black Sea Lowland is drained by the lower reaches of the Dnister River, the Boh River, the Dnipro River, and other smaller rivers flowing into the Black Sea and the Sea of Azov. To the south and east small intermittent streams drain the Crimean Lowland and small, though mostly permanent, streams drain the Kuban Lowland into the Sea of Azov. The mean annual precipitation ranges between 270 and 400 mm (up to 500 mm in the Kuban Lowland); the mean annual runoff, occurring mostly in the spring, is less than 25 mm (6 percent or less) in the dry steppe and up to to 50 mm (10 percent) in the Kuban Lowland. In the summer nearly all the water evaporates, and small streams and middle-sized rivers, such as the Malyi Kuialnyk River, the Velykyi Kuialnyk River, and the Tylihul River, tend to dry up. Lacking sufficient power such rivers flow into coastal terminal lakes, which are cut off from the sea by shoreline bars. River valleys are broad with low banks and floodplains overgrown with reeds. The ice cover is not always stable; it lasts up to 2.5 months.

The Crimean Mountains obtain 400–1,000 mm of mean annual precipitation, mostly in the late fall and the winter. A large proportion of the rainfall is absorbed by the porous limestones (underground drainage); there is left a mean annual runoff of 20–200 mm (5–20 percent). The short mountain streams form deep, narrow gorges. Those flowing north onto the Crimean Lowland become intermittent and assume characteristics common to the smaller rivers of the Black Sea Lowland.

The Carpathian Mountains and Subcarpathia are drained to the north by the right-bank tributaries of the upper Vistula River (the Dunajec River, the Wisłoka River, and the Sian River) and by the Dnister River headwaters, including its left-bank tributary, the Stryvihor River, and its many right-bank tributaries, such as the Bystrytsia River, the Stryi River, the Svicha River, the Limnytsia River, the Bystrytsia Solotvynska River, and the Bystrytsia Nadvirnianska River. To the south the Carpathians are drained by the Tysa River with its right-bank tributaries, the Teresva River, the Tereblia River, the Rika River, the Borzhava River, the Liatorytsia River, the Uzh River, the Laborets River, and the Ondava River with its tributary, the Toplia River. To the east the Carpathians are drained by the headwaters of the left-bank tributaries of the Danube River, the Seret (Siret) River and the Prut River. The mean annual precipitation varies widely, from 700 mm in the foothills to 1,500 mm at the highest mountain elevations. The mean annual runoff also varies, in keeping with the elevation, from 350 to 750 mm (50 percent or more). River density is 1.1 km/sq km. Gradients are very steep, 60–70 m/km, in the upper reaches but decline to 5–10 m/km in the lower reaches. River valleys in the mountains are relatively narrow and deep (600–800 m), in the foothills, less so (150–250 m). Summer flash floods are not uncommon. The ice cover varies from 2.5 to 4 months, according to the elevation. Almost every winter the ice cover in the foothills is interrupted by thaws. The middle reaches of the Tysa lack a permanent ice cover in winter. Rivers carry a large quantity of material in suspension, but not in solution.

The Western Subcaucasia is drained by the Kuban River and its left-bank (southern) tributaries, the Zelenchuk rivers (the Zelenchuk Malyi and the Zelenchuk Velykyi), the Laba River, the Bila River, and the Pshysh River. The mean annual precipitation increases from 500 mm in the lower reaches of the Kuban to 1,000 mm in the foothills and 2,400 mm in the Caucasus Mountains. Runoff in the mountains attains or exceeds 50 percent of the precipitation; in the lowland it remains at 10 percent. Rivers are fed by rainfall, snow, and glaciers. Valleys in the mountains are deep and narrow; in the lowland they are wide, with gentle slopes. An ice cover does not form every year.

In the past, rivers provided settlements with water supply, transportation, and fishing. Recently river transport and river fisheries have declined in significance, and the role played by rivers in municipal and industrial water supply, irrigation, drainage, the removal of sewage and industrial effluents, and the generation of hydroelectric power has increased. Rivers also serve as sites for outdoor recreation and as routes for tourism, but with increasing water pollution the quality of their waters and hence their value for municipal, industrial, and recreational uses have declined.

BIBLIOGRAPHY
Ohiievs’kyi, A. Hidrolohiia (Kharkiv–Kyiv 1933)
Davydov, L. Gidrografiia SSSR (Vody sushi), 2 vols (Leningrad 1953–5)
Chyppynh, H.; Lysenko K. Richnyi ta minimal’nyi stik na terytoriï Ukraïny (Kyiv 1959)
Hidrolohichni rozrakhunky dlia richok Ukraïny (Kyiv 1962)
Shvets' H. Kharakterystyka vodnosti richok Ukrainy (Kyiv 1964)
L'vovich, M. Reki SSSR (Moscow 1971)
Priroda Ukrainskoi SSR: Moria i vnutrennie vody (Kyiv 1987)

Ihor Stebelsky, Ivan Teslia

[This article originally appeared in the Encyclopedia of Ukraine, vol. 4 (1993).]