Water reservoirs
In conditions of Belarus the group (more than 30%) of recreation-tourist zone and resort locations of republican importance is formed on lake system, about 30% is on reservoir system and 40% is on rivers.
The location of Bealrus in the zone of humidity and the pecularities of geological structure and relief caused the development of hydrographic net including rivers, ponds and lakes. The building of canals in Belarus increased the number of water reservoirs.
Rivers of Belarus.
In Belarus there are 20,8 thousand rivers, their total length makes 90,6 thousand km. Both by length and by quantity prevail small rivers (length to 100 km) and streams (length to 10 km.) – they make 93 % of total amount and 53 % of total length of all rivers. There are 42 (0,2 % from total of all rivers) with length from 101 to 500 km in Belarus. And only 9 rivers have length more than 500 km. They are the follwoing Berezina (throughout all the territory), Neman, Vilija (start from the territory of Belarus), Zapadnaya Dvina, Dnepr, Sozh, Pripyat, Goryn and Western Bug (transit).
The considerable quantity of small rivers is explained by the fact that on territory of Belarus takes place Chernomorsko-Baltic watershed. The watershed is stretched through northwest suburb of Polesye, on the Kopylsky ridge, Minsk and Orshansky uplands. 57 % of territory of Belarus refer to the pool of the Black Sea (Dnepr with Pripyat, Berezina and Sozh), and 43 % — to the Baltic (Neman, Zapadnaya Dvina, Western Bug, Lovat).
The most widespread flat small rivers are in rather superficial well developed wide valleys with gentle slopes. Twisting channel with alternation of reaches and rifts, small inclinations of water table, slow current are characteristic for them. In borders of heights the valley of rivers is more expressive, the current becomes more rash. In the south of Belarus there is a lot of rivers flowing through marshes or having marshy places as a part of the reservoir. In the north of the country the considerable part is made by the rivers which start in lakes or flow through them.
Channels which are characteristic for Belarus flat and lowland rivers usually twisting, somewhere are divided into branches. On uplands channels are more expressive, without branches and canals. From river dereliction the following are formed riffles, spits, islands, beaches and shoals. In the north of Belarus channels are twisting without branches. Their width basically makes 10 – 20 m, in the bottom currents – 30 – 50 m. The width of large rivers usually makes 80 – 120 m, in some places to 300 – 500 m. Depth differs from 0,5 to 1 m, in river reaches – from 2 to 4 m, in some places to 8 m. The bottom of such rivers are mostly sandy and sandy-silty, in the northwest in some places it is stony and rapids. In the south of our country channels of rivers are twisting, branched out, often there are cutoff meander, meliorative channels. The width of channel differs from 5 – 10 m in upper courses to 20 – 40 m in bottom currents, in some places to 60 – 80 m. Depth changes from 0,1 – 0,3 m to 7 m in separate places. Low sandy islands are seen.
The river valleys occupy almost 10% of the territory of Belarus. On the south from the border of the last ice age modern river valleys are wide, rather shallow, often assimetric. The youngest valleys are in Belarusian Poozerie. They are usually deep (20 – 30 m) and rather narrow, in some places similiar to canyons with steep slopes, floodplains are narrow or absent.
The average speed of big and medium rivers is 0,5 – 0,7 m/s, on the riffles to 0,8 – 1,5 m/s, on the rapids of small rivers more than 1,5 m/s. The maximum speeds are during clearing and flood, the minimal are during the low water.
The main source of river nourishment are atmospheric precipitations. For rivers in Belarus the following factors are characteristic: spring clearing and steady summer and autumn and winter low waters which sometimes are broken by floods from rains in summer and during thaws in winter.
In winter rivers are frozen for 80 – 140 days. The freezing starts with the temperature above 0ºС in the second decade from November from the north to the south-west and south. The thickness of ice on the north and north-east is 29 – 64 sm, on the west and south-west – 22 – 57 sm, on the south – 17 – 45 sm. Almost everywhere there is spring drifting. In some severe winters some rivers can be frozen till the bottom but thi is not characteristic for Belarus.
Average month temperature of waters in rivers in July is 19 - 22 ºС (in some days to 27С) with maximum at 16 – 18 hours, minimum at 6 – 8 hours.
Characteristics of rivers of the Black Sea.
The rivers of Belarus form the following river pools: Dnepr, Pripyat, Western Dvina, Neman, Eastern Boug, Vilya and Lovat.
The biggest area pool is formed by Dnepr and its tributaries. On the territory of Belarus it occupies almost 64 thous. km2. Dnepr is the biggest river of Belarus. It starts on Valday upland in Russia and flows to Dnepr coastal lake of the Black Sea in Ukraine. With total length the river Dnepr 2145 km, in the average stream on the distance of 700 km it flows on the territory of Belarus where gets its main tributaries - rivers Pripyat, Sozh and Berezina.
Approximately to Shklov Dnepr flows in a narrow valley with high abrupt coast. Slopes of valley of the river in height of 12-35 m are cut by broad gulls, valleys of inflows and drying channels. Lower the valley becomes gradually wider, and the channel is twisting with numerous bends, rifts. Down the mouth of the river Drut the coasts of Dnepr start to get Polesye kind. In floodplain the quantity of small lakes-starits increases. The width of the river is from 15 - 120 m in its headwaters on the territory of Belarus to 800 - 1500 m on the border with Ukraine. The spring high water lasts 2 - 2,5 months, and during its water level usually rises on 4 - 6 m and more.
The largest right inflows of Dnepr are Drut and Berezina, the left is Sozh. Almost all river navigable,there are many river landing stages and 2 ports on it - in Mogilyov and Retchitsa.
The second river pool for the sizes within Belarus forms Pripyat . The area of the river within the country is less than 53 thousand km2. The river starts in the west of the Ukrainian Polesye (Volynsk area) and from the west on the east crosses Polessky lowland. On territory of Belarus it is 500 km long. The river network consists of 10.5 thousand rivers and streams, including waterways in length less than 10 km. Total length of the river network is over 47 thousand km. Streams make 93 % from total number of water currents, and their total length is equal to almost 55 % of length of the whole river network. The main inflows of the river Pripyatare: the rivers Pina, Jaselda, Bobrik, Tsna, Lan, Sluch, Ptich, Tremlja, Ipa, Stohod, Styr, Goryn, Stviga, Ubort, Slovechna. Pripyat is the deepest inflow of Dnepr into which runs outside of the country.
The rivers floodplain is wide and strongly boggy, with a considerable quantity of cut-off meander and channels. On the uplands there are inundated oak groves. The floodplain is wide from 1 - 2 to 16 - 18 km. In places the width of floodplain reaches 30 km. The channel of the river Pripyat is twisting, in many places branched out. Only down Mozyr in borders of end-moraine ridge the channel is direct without branches. The channel gradually extends from 40 - 60 m in upper courses to 200 - 300 m on the border with Ukraine. The coast of Pripyat is basically flat, on bends are sometimes steep. The bottom is mainly sandy, therefore the muddiness of rivers is small. In the spring the water level is low, usually on 2 - 3 m, but floods big territory. The spring high water lasts about 3 months. Pripyat on the whole territory of Belarus is navigable.There are ports Pinsk and Mozyr, and also numerous river landing stages are located.
Characteristics of rivers of the Baltic Sea.
The Northwest part of Belarus is occupied with pool of Neman . On total length Neman concedes only to Dnepr and Western Dvina. Within Belarus it was stretched on 459 km. The reservoir area is about 35 thousand km2. The river starts on Minsk upland — in Uzdensky area, further proceeds among picturesque wood landscapes.
In river headwaters the floodplain is wide (2-4 km). On the medium part from a mouth of the river Kotra on the north to the river Vilija the river valley is rather deep and narrow, the channel bottom is stony, thresholds and rifts are formed. On the bottom site, after the confluence of the river Vilija, the channel straightenes and extends almost in two times. Its bottom becomes sandy, the river has many islands. As a whole the width of the valley of the river Neman mainly makes 1-4 km.
The width of channel in upper courses is 35-40 m, down the current it increases to 90 m, down to the river confluence Shchara, to 120-150 m and in the bottom current - of 180-380 m, to 640 m.
The hydrographic network is mostly developed by places on the left bank. As a whole for river pool Neman the dense river network is characteristic. From the source to the mouth the river accepts about 180 inflows. The largest right inflows of Neman are Vilija, the Western Berezina, Ditva, Kotra, left - Shchara and Zelvjanka.
Northern areas of Belarus are covered by a river pool Western Dvina with the area within the country of 33 thousand km2. The pool almost coincides with borders of Belarus Poozerja and Vitebsk area. As well as Dnepr, the river starts on Valdai upland, but flows into the Baltic Sea through Russia, Belarus and Latvia. On total length Western Dvina concedes only to Dnepr. Within Belarus its length makes 328 km.
Western Dvina proceeds mainly on lowlands: Surazhsky and Polotsk. In pool of Western Dvina numerous lakes are located, the majority of them are connected with the river system. The largest right inflows are Obol, Drissa, left - Luchosa, Ulla, Disna. The channel of the river Western Dvina in width is 120 - 300 m and coasts in height are 10 - 40 m. It is characterised by a considerable quantity of sandy islands, rifts and thresholds. The valley has the trapeze form, at village Ruba (Vitebsk area) the form is of canyon. The width, basically, is 3 - 4 km, in some places to 10 - 15 km. In the valley structure the floodplain and two floodplain terraces are observed. The width of the floodplain is usually to 300 - 500 m.
The severe climate and features of the valley structure of Western Dvina have caused the most extended period with the ice phenomena and the highest lifting of water level during spring high water (9 - 12). The whole river is navigable.
In the northeast of Belarus there is a small river pool Lovat. Southwest areas are occupied with pool of the Western Bug. This river starts on slopes of the Podolsk height in Ukraine (Lvov area), bears the waters on borders of Belarus and Poland and near Warsaw runs into Vistula. On territory of Belarus the length of the river is 154 km, and the area of pool is about 11 thousand km. The width of the river valley varies from 1 - 3 to 7 km and more. Floodplain is seen everywhere, its width fluctuates from several tens metres to 2 - 4 km at flowing into the rivers Muhovets and Lesnaya. The channel is rather weak its width is 50 - 75 m, in some places 200 - 300 m. The main inflows of the river on the republic territory are the rivers Kopaevka, Muhavets, Lesnaya, Pulva.
Channels of Belarus.
Belonging to the rivers to different pools and plain watersheds for a long time promoted the building of ship canals. The largest among them are Dneprovsko-Bugsky, August, Oginsky, Mikashevichsky channels, Berezinsky and Vilejsko-Minsk water systems.
The largest and important on economic value is Dneprovsko-Bugsky channel. It connects the river Pina (inflow of Pripyat) and the river Muhavets (inflow of Bug). The channel is 196 km long, including channeled parts of the rivers Pina and Muhavets. Channel building was held in XVIII - XIX centuries? after it it was repeatedly restored.
River systems of Neman and Visla are connected by August channel the part of which is located in Poland and in Grodno. The channel was built in the beginning of XIX century. Its general length is 102 km, on territory of modern Belarus is 22 km. The channel represents system of lakes, ponds, channeled rivers and inflows. After building railways and highways has lost the transport value. The Polish and Belarusian parts of the channel are restored and used in the tourist purposes.
In second half of XX century Vilejsko - Minsk water system was built. It connects the rivers Vilija and Svisloch and includes Vilejsky and Zaslavsky water reservoirs, the system of channels in length more than 60 km.
Besides listed, on the territory of Belarus the considerable quantity of meliorative channels is constructed. The largest of them is Slavkovichsko-Jaminsky. The total length of meliorative channels is more than 150 thousand km.
Lakes in Belarus.
On the territory of Belarus there are more than 10 thousand lakes. There are 1072 lakes with the area 0,1 км², with the area 10 км² there are 20. The largest by the area is lake Naroch (79,6 км²). The greatest by the area are the following lake Osvejsky (52,8 км²), Chervonoe (40,8 км²), Lukomsky (37,7 км²), Drivjaty (36,1 км²) Etc. The greatest part of lakes are in the north of the country – in Belarus Poozerie and in the south – in Belarus Polesye. In separate areas (Braslavsky, Ushachsky) lakes occupy 10 % of territory.
The depth of lakes changes from 0,3 m, reaching the maximum value of 53,7 m in lake Dolgoe Gluboksky area. About 40 % of lakes are shallow, with the maximum depth less than 5 m, a share of lakes with depths of 5-10 m makes 30 % and 6 % is reservoirs with depths more than 25 m.
The water level in lakes within a year practically does not change and usually fluctuates from 1 to 1,5 m, in spring it raises, in winter and in summer goes down.
In summer shallow lakes under the influence of a wind mix up to the bottom, and water gets warm to 18 - 20º C. In deep lakes only top layer gets warm, in the medium layer the temperature goes down on 3 - 5º C on each metre. In winter lakes during 4 – 5 months are covered by ice in the thickness 50 - 70 sm
On chemical compound lakes of Belarus concern to fresh, hydrocarbonate-calcium. Their general mineralization makes 200 – 300 mg/l. The basic mineralization components are: hydrocarbonate ion (НСО³ˉ), ion of Са²+, Mg²+, SO4²ˉ, Clˉ . Chlorides and sulphates meet in small amount and increase as a result of economic activities of people. In pure water there is not enough basic biogene substances (connections of nitrogen, phosphorus). Concentration of iron in benthonic layers makes 2 – 3 mg/l. The basic hydrochemical indicator – active reaction of water (рН) – changes in lakes from subacidic (6 – 6,5) in the conditions of marsh food in winter to alkaline (8 – 8,5) in most cases рН makes 7,5 – 8.
Lakes form unique lake landscapes and water-marsh complexes (lakes of marshes Yelnya, Braslavsky, Narochansky group, system of the rivers Drysa, Vygonoshchansky, Osvejsky, etc.), The most unique lakes are included in the system of especially protected natural territories and serve as their kernel of protection. Within protected territories of republic there are 255 lakes with the total area nearby 604 км² that makes more than 3,7 % of protected territories of republic.
Many lakes are located close to each other, connected by channels and form lake groups. The most known among them are: the Braslavsky group including more of 30 lakes with the total area 113 км2; Narochansky group of 4 lakes with the area nearby 100 км2; Ushachsky group of 60 lakes with the area of nearby 75 км2. All of them are located on the territory of Belarus Poozerja. Hollows of these lakes have a glacial origin. Lakes of northern part of the country usually have well expressed coast, abrupt and high slopes.
Types of glacial hollows:
The location of Bealrus in the zone of humidity and the pecularities of geological structure and relief caused the development of hydrographic net including rivers, ponds and lakes. The building of canals in Belarus increased the number of water reservoirs.
Rivers of Belarus.
In Belarus there are 20,8 thousand rivers, their total length makes 90,6 thousand km. Both by length and by quantity prevail small rivers (length to 100 km) and streams (length to 10 km.) – they make 93 % of total amount and 53 % of total length of all rivers. There are 42 (0,2 % from total of all rivers) with length from 101 to 500 km in Belarus. And only 9 rivers have length more than 500 km. They are the follwoing Berezina (throughout all the territory), Neman, Vilija (start from the territory of Belarus), Zapadnaya Dvina, Dnepr, Sozh, Pripyat, Goryn and Western Bug (transit).
The considerable quantity of small rivers is explained by the fact that on territory of Belarus takes place Chernomorsko-Baltic watershed. The watershed is stretched through northwest suburb of Polesye, on the Kopylsky ridge, Minsk and Orshansky uplands. 57 % of territory of Belarus refer to the pool of the Black Sea (Dnepr with Pripyat, Berezina and Sozh), and 43 % — to the Baltic (Neman, Zapadnaya Dvina, Western Bug, Lovat).
The most widespread flat small rivers are in rather superficial well developed wide valleys with gentle slopes. Twisting channel with alternation of reaches and rifts, small inclinations of water table, slow current are characteristic for them. In borders of heights the valley of rivers is more expressive, the current becomes more rash. In the south of Belarus there is a lot of rivers flowing through marshes or having marshy places as a part of the reservoir. In the north of the country the considerable part is made by the rivers which start in lakes or flow through them.
Channels which are characteristic for Belarus flat and lowland rivers usually twisting, somewhere are divided into branches. On uplands channels are more expressive, without branches and canals. From river dereliction the following are formed riffles, spits, islands, beaches and shoals. In the north of Belarus channels are twisting without branches. Their width basically makes 10 – 20 m, in the bottom currents – 30 – 50 m. The width of large rivers usually makes 80 – 120 m, in some places to 300 – 500 m. Depth differs from 0,5 to 1 m, in river reaches – from 2 to 4 m, in some places to 8 m. The bottom of such rivers are mostly sandy and sandy-silty, in the northwest in some places it is stony and rapids. In the south of our country channels of rivers are twisting, branched out, often there are cutoff meander, meliorative channels. The width of channel differs from 5 – 10 m in upper courses to 20 – 40 m in bottom currents, in some places to 60 – 80 m. Depth changes from 0,1 – 0,3 m to 7 m in separate places. Low sandy islands are seen.
The river valleys occupy almost 10% of the territory of Belarus. On the south from the border of the last ice age modern river valleys are wide, rather shallow, often assimetric. The youngest valleys are in Belarusian Poozerie. They are usually deep (20 – 30 m) and rather narrow, in some places similiar to canyons with steep slopes, floodplains are narrow or absent.
The average speed of big and medium rivers is 0,5 – 0,7 m/s, on the riffles to 0,8 – 1,5 m/s, on the rapids of small rivers more than 1,5 m/s. The maximum speeds are during clearing and flood, the minimal are during the low water.
The main source of river nourishment are atmospheric precipitations. For rivers in Belarus the following factors are characteristic: spring clearing and steady summer and autumn and winter low waters which sometimes are broken by floods from rains in summer and during thaws in winter.
In winter rivers are frozen for 80 – 140 days. The freezing starts with the temperature above 0ºС in the second decade from November from the north to the south-west and south. The thickness of ice on the north and north-east is 29 – 64 sm, on the west and south-west – 22 – 57 sm, on the south – 17 – 45 sm. Almost everywhere there is spring drifting. In some severe winters some rivers can be frozen till the bottom but thi is not characteristic for Belarus.
Average month temperature of waters in rivers in July is 19 - 22 ºС (in some days to 27С) with maximum at 16 – 18 hours, minimum at 6 – 8 hours.
Characteristics of rivers of the Black Sea.
The rivers of Belarus form the following river pools: Dnepr, Pripyat, Western Dvina, Neman, Eastern Boug, Vilya and Lovat.
The biggest area pool is formed by Dnepr and its tributaries. On the territory of Belarus it occupies almost 64 thous. km2. Dnepr is the biggest river of Belarus. It starts on Valday upland in Russia and flows to Dnepr coastal lake of the Black Sea in Ukraine. With total length the river Dnepr 2145 km, in the average stream on the distance of 700 km it flows on the territory of Belarus where gets its main tributaries - rivers Pripyat, Sozh and Berezina.
Approximately to Shklov Dnepr flows in a narrow valley with high abrupt coast. Slopes of valley of the river in height of 12-35 m are cut by broad gulls, valleys of inflows and drying channels. Lower the valley becomes gradually wider, and the channel is twisting with numerous bends, rifts. Down the mouth of the river Drut the coasts of Dnepr start to get Polesye kind. In floodplain the quantity of small lakes-starits increases. The width of the river is from 15 - 120 m in its headwaters on the territory of Belarus to 800 - 1500 m on the border with Ukraine. The spring high water lasts 2 - 2,5 months, and during its water level usually rises on 4 - 6 m and more.
The largest right inflows of Dnepr are Drut and Berezina, the left is Sozh. Almost all river navigable,there are many river landing stages and 2 ports on it - in Mogilyov and Retchitsa.
The second river pool for the sizes within Belarus forms Pripyat . The area of the river within the country is less than 53 thousand km2. The river starts in the west of the Ukrainian Polesye (Volynsk area) and from the west on the east crosses Polessky lowland. On territory of Belarus it is 500 km long. The river network consists of 10.5 thousand rivers and streams, including waterways in length less than 10 km. Total length of the river network is over 47 thousand km. Streams make 93 % from total number of water currents, and their total length is equal to almost 55 % of length of the whole river network. The main inflows of the river Pripyatare: the rivers Pina, Jaselda, Bobrik, Tsna, Lan, Sluch, Ptich, Tremlja, Ipa, Stohod, Styr, Goryn, Stviga, Ubort, Slovechna. Pripyat is the deepest inflow of Dnepr into which runs outside of the country.
The rivers floodplain is wide and strongly boggy, with a considerable quantity of cut-off meander and channels. On the uplands there are inundated oak groves. The floodplain is wide from 1 - 2 to 16 - 18 km. In places the width of floodplain reaches 30 km. The channel of the river Pripyat is twisting, in many places branched out. Only down Mozyr in borders of end-moraine ridge the channel is direct without branches. The channel gradually extends from 40 - 60 m in upper courses to 200 - 300 m on the border with Ukraine. The coast of Pripyat is basically flat, on bends are sometimes steep. The bottom is mainly sandy, therefore the muddiness of rivers is small. In the spring the water level is low, usually on 2 - 3 m, but floods big territory. The spring high water lasts about 3 months. Pripyat on the whole territory of Belarus is navigable.There are ports Pinsk and Mozyr, and also numerous river landing stages are located.
Characteristics of rivers of the Baltic Sea.
The Northwest part of Belarus is occupied with pool of Neman . On total length Neman concedes only to Dnepr and Western Dvina. Within Belarus it was stretched on 459 km. The reservoir area is about 35 thousand km2. The river starts on Minsk upland — in Uzdensky area, further proceeds among picturesque wood landscapes.
In river headwaters the floodplain is wide (2-4 km). On the medium part from a mouth of the river Kotra on the north to the river Vilija the river valley is rather deep and narrow, the channel bottom is stony, thresholds and rifts are formed. On the bottom site, after the confluence of the river Vilija, the channel straightenes and extends almost in two times. Its bottom becomes sandy, the river has many islands. As a whole the width of the valley of the river Neman mainly makes 1-4 km.
The width of channel in upper courses is 35-40 m, down the current it increases to 90 m, down to the river confluence Shchara, to 120-150 m and in the bottom current - of 180-380 m, to 640 m.
The hydrographic network is mostly developed by places on the left bank. As a whole for river pool Neman the dense river network is characteristic. From the source to the mouth the river accepts about 180 inflows. The largest right inflows of Neman are Vilija, the Western Berezina, Ditva, Kotra, left - Shchara and Zelvjanka.
Northern areas of Belarus are covered by a river pool Western Dvina with the area within the country of 33 thousand km2. The pool almost coincides with borders of Belarus Poozerja and Vitebsk area. As well as Dnepr, the river starts on Valdai upland, but flows into the Baltic Sea through Russia, Belarus and Latvia. On total length Western Dvina concedes only to Dnepr. Within Belarus its length makes 328 km.
Western Dvina proceeds mainly on lowlands: Surazhsky and Polotsk. In pool of Western Dvina numerous lakes are located, the majority of them are connected with the river system. The largest right inflows are Obol, Drissa, left - Luchosa, Ulla, Disna. The channel of the river Western Dvina in width is 120 - 300 m and coasts in height are 10 - 40 m. It is characterised by a considerable quantity of sandy islands, rifts and thresholds. The valley has the trapeze form, at village Ruba (Vitebsk area) the form is of canyon. The width, basically, is 3 - 4 km, in some places to 10 - 15 km. In the valley structure the floodplain and two floodplain terraces are observed. The width of the floodplain is usually to 300 - 500 m.
The severe climate and features of the valley structure of Western Dvina have caused the most extended period with the ice phenomena and the highest lifting of water level during spring high water (9 - 12). The whole river is navigable.
In the northeast of Belarus there is a small river pool Lovat. Southwest areas are occupied with pool of the Western Bug. This river starts on slopes of the Podolsk height in Ukraine (Lvov area), bears the waters on borders of Belarus and Poland and near Warsaw runs into Vistula. On territory of Belarus the length of the river is 154 km, and the area of pool is about 11 thousand km. The width of the river valley varies from 1 - 3 to 7 km and more. Floodplain is seen everywhere, its width fluctuates from several tens metres to 2 - 4 km at flowing into the rivers Muhovets and Lesnaya. The channel is rather weak its width is 50 - 75 m, in some places 200 - 300 m. The main inflows of the river on the republic territory are the rivers Kopaevka, Muhavets, Lesnaya, Pulva.
Channels of Belarus.
Belonging to the rivers to different pools and plain watersheds for a long time promoted the building of ship canals. The largest among them are Dneprovsko-Bugsky, August, Oginsky, Mikashevichsky channels, Berezinsky and Vilejsko-Minsk water systems.
The largest and important on economic value is Dneprovsko-Bugsky channel. It connects the river Pina (inflow of Pripyat) and the river Muhavets (inflow of Bug). The channel is 196 km long, including channeled parts of the rivers Pina and Muhavets. Channel building was held in XVIII - XIX centuries? after it it was repeatedly restored.
River systems of Neman and Visla are connected by August channel the part of which is located in Poland and in Grodno. The channel was built in the beginning of XIX century. Its general length is 102 km, on territory of modern Belarus is 22 km. The channel represents system of lakes, ponds, channeled rivers and inflows. After building railways and highways has lost the transport value. The Polish and Belarusian parts of the channel are restored and used in the tourist purposes.
In second half of XX century Vilejsko - Minsk water system was built. It connects the rivers Vilija and Svisloch and includes Vilejsky and Zaslavsky water reservoirs, the system of channels in length more than 60 km.
Besides listed, on the territory of Belarus the considerable quantity of meliorative channels is constructed. The largest of them is Slavkovichsko-Jaminsky. The total length of meliorative channels is more than 150 thousand km.
Lakes in Belarus.
On the territory of Belarus there are more than 10 thousand lakes. There are 1072 lakes with the area 0,1 км², with the area 10 км² there are 20. The largest by the area is lake Naroch (79,6 км²). The greatest by the area are the following lake Osvejsky (52,8 км²), Chervonoe (40,8 км²), Lukomsky (37,7 км²), Drivjaty (36,1 км²) Etc. The greatest part of lakes are in the north of the country – in Belarus Poozerie and in the south – in Belarus Polesye. In separate areas (Braslavsky, Ushachsky) lakes occupy 10 % of territory.
The depth of lakes changes from 0,3 m, reaching the maximum value of 53,7 m in lake Dolgoe Gluboksky area. About 40 % of lakes are shallow, with the maximum depth less than 5 m, a share of lakes with depths of 5-10 m makes 30 % and 6 % is reservoirs with depths more than 25 m.
The water level in lakes within a year practically does not change and usually fluctuates from 1 to 1,5 m, in spring it raises, in winter and in summer goes down.
In summer shallow lakes under the influence of a wind mix up to the bottom, and water gets warm to 18 - 20º C. In deep lakes only top layer gets warm, in the medium layer the temperature goes down on 3 - 5º C on each metre. In winter lakes during 4 – 5 months are covered by ice in the thickness 50 - 70 sm
On chemical compound lakes of Belarus concern to fresh, hydrocarbonate-calcium. Their general mineralization makes 200 – 300 mg/l. The basic mineralization components are: hydrocarbonate ion (НСО³ˉ), ion of Са²+, Mg²+, SO4²ˉ, Clˉ . Chlorides and sulphates meet in small amount and increase as a result of economic activities of people. In pure water there is not enough basic biogene substances (connections of nitrogen, phosphorus). Concentration of iron in benthonic layers makes 2 – 3 mg/l. The basic hydrochemical indicator – active reaction of water (рН) – changes in lakes from subacidic (6 – 6,5) in the conditions of marsh food in winter to alkaline (8 – 8,5) in most cases рН makes 7,5 – 8.
Lakes form unique lake landscapes and water-marsh complexes (lakes of marshes Yelnya, Braslavsky, Narochansky group, system of the rivers Drysa, Vygonoshchansky, Osvejsky, etc.), The most unique lakes are included in the system of especially protected natural territories and serve as their kernel of protection. Within protected territories of republic there are 255 lakes with the total area nearby 604 км² that makes more than 3,7 % of protected territories of republic.
Many lakes are located close to each other, connected by channels and form lake groups. The most known among them are: the Braslavsky group including more of 30 lakes with the total area 113 км2; Narochansky group of 4 lakes with the area nearby 100 км2; Ushachsky group of 60 lakes with the area of nearby 75 км2. All of them are located on the territory of Belarus Poozerja. Hollows of these lakes have a glacial origin. Lakes of northern part of the country usually have well expressed coast, abrupt and high slopes.
Types of glacial hollows:
- Pondage. They were formed under the influence of thawed glacial waters in falls between morainic ridges, have round form and dissymetric slopes (lakes Naroch, Osvejsky, Mjadel, Drivjaty, Lukomsky, etc.);
- Coomb. Were formed as a result of ploughing by ice narrow deep hollows depth to 80 – 100 m and activity of thawed glacial waters (Dolgoe, Senno, Saro, Balduk, etc.);
- Evorzion. Appeared as a result of destructive activity of water which falls flew down from glacier and beat out small, but deep (25 – 30) bowls with abrupt slopes and roundish drawing of a coastal line (Rudakovo, Visjaty, Voronets, Light, etc.);
- Frost-thaw. Appeared on the place of thawing glacial lenses during glacier deviation. They are small and superficial (Lisitsky, Usomlja, Kanashi).
Braslavsky lake system is located in Braslavsky area on border with Lithuania and Latvia. To the number of the largest, with the area of more than 1,0 km² refer about 20 reservoirs, their general quantity reaches 50. Formation of Braslavsky lakes is connected with the activity and recession of poozerie ice. Basically they are located within the Braslavsky upland. The basic waterway of the system is the river Drujka - the left inflow of the river Western Dvina uniting the largest lakes. The general lake number makes about 11 %.
Narochansky lake system with the total area of water mirror up to 100 км² it is located in Mjadelsky district Minsk region. It is drained by small left inflow of the river Vilija - the river of Naroch. The general reservoir of all lakes makes 279 км². Hollows of Narochansky lakes refer to pondage type.