Geography of the White Sea and its watershed

This chapter presents the geography of the White Sea - or Beloye More - and surrounding land areas. The main geographic features of the White Sea per se are described in Section 1.1. Section 1.2 characterizes the bottom topography or bathy- metry, including a new digital model of the sea bottom relief. Section 1.3 gives an account of the physical geography of the catchment area or watershed draining into the White Sea. Section 1.4 is a more detailed description of the physical geography and climatic characteristics of the various areas within the watershed.

1.1 MAIN FEATURES OF THE WHITE SEA

The White Sea (Figure 1.1, see color section) is a marginal shelf sea, with a total area of 90,800 km2, including islands. The mean depth is 67 m and the maximum depth is 350 m (Atlas of the Oceans, 1980). The total volume of the sea is 6,000 km3. The coastline length is 5,093 km. The greatest width (450 km) is between Arkhangelsk and Kandalaksha. The White Sea can be divided conveniently into three parts (i.e., northern, central, and southern).

The White Sea is essentially a mediterranean sea, which is semi-enclosed by surrounding land areas. The northern part of the sea is connected to the Barents Sea through a strait called Voronka (Funnel). The southern and central parts of the White Sea, called Bassein (Pool), are the largest and deepest parts of the sea. There are also several large bays in the area, namely the Dvinskiy, Onezhskiy, Mezenskiy, and Kandalakshkiy Bays. The Gorlo (Throat) is a narrow strait connecting Basein and Voronka. The length of the Gorlo Strait is 170 km and its width is "' 45-55 km. The eastern coast of the White Sea is relatively low and is a part of the Russian platform. The southern coast is mainly composed of Quaternary deposits. The western coast and islands consist of metamorphic rocks, mainly granite-gneiss. The north-west coast near Kandalakshkiy Bay is of tectonic origin. The Terskiy

and Abramovskiy coasts are very low and flat consisting largely of clay deposits. The Kanin coast is mostly high, interrupted by river inflows and estuaries where it qualifies as a lowland. The northern part of the Konushinskiy coast is relatively low, whereas its southern part has sharp rises. The Zimniy (figuratively, winter ) coast of the Gorlo is rather high. Both the Zimniy and Letniy (figuratively,

summer ) coasts of the Dvinskiy Bay are steep almost along their entire span. The Pomorskiy and Karelian coasts of the Onezhskiy Bay are mostly lowlands. The Karelian coast between the Onezhskiy and Kandalakshkiy Bays is rocky and relatively high.

The White Sea hosts numerous islands, scattered predominantly in the Onezhskiy and Kandalakshkiy Bays. The total area of the islands is about 800 km2(The White Sea, 1985). The islands of the Solovetskiy Archipelago, located between the Onezhskiy Bay and the Bassein, are the largest. Numerous islands are also present in the Dvinskiy Bay, with many of them situated in the Northern Dvina estuary.

1.2 BOTTOM TOPOGRAPHY

The White Sea is shallow, with a mean depth of 67 m. Nonetheless, the bottom relief of the sea is irregular and complicated. The northern part of the sea is rather shallow, though in the northern part of the Voronka region, depths can reach 60-70 m. In the offshore part of Mezenskiy Bay, depths are less than 20 m. The bottom relief in this part of the sea is very uneven and is similar to the bottom relief of the Gorlo. Several troughs are found along the middle part of the strait. Average depths in the Gorlo vary between 30-50 m. The water exchange between the White and Barents Seas varies considerably due to the uneven bathymetry and also on the particular season. It plays an important role in the development of hydrophysical, hydrochemical, and hydrological regimes of the sea. The Bassein is the deepest part of the sea. The central depression, with depths exceeding 100 m, extends from north-west to south-east (i.e., from Kandalakshskiy Bay to Dvinskiy Bay) and occupies approxi- mately two-thirds of the Bassein s water area. Three depressions intersected by thresholds are located here. Onezhskiy Bay is separated from the central part of the sea by the Solovetskiy Archipelago. This is the shallowest part, with a depth ranging from 5-25 m. The bottom relief features of the basin and deepwater parts of the Kandalakshskiy and Dvinskiy Bays are rather similar. The bottom relief of Onezhskiy Bay is very uneven. There are numerous stony banks, many of which are given specific local names such as Korga and Luda .

The shallowest part of the northern White Sea has a ridge-type relief formed by tidal currents. Its depth, on average, is 30-50 m, and it increases (up to 60-70 m) closer to the boundary conditionally separating the White Sea from the Barents Sea. The central region of the sea is leveled due to the accumulated sediments (The Arctic and Antarctic Oceans, 1985); its major part is occupied by the Central Deep with depths over 100 m.

A characteristic feature of the north-western part of the White Sea is the

Sec. 1.2]

Kandalaksha Depression - a large and deep graben that reaches 350 m, the maximum depth of the White Sea (Atlas of the Oceans, 1980; The Arctic and Antarctic Oceans, 1985). In contrast to most of the White Sea, the shores of the northern part are slightly incised, with only the Gorlo region having several small bays.

The morphometric features and the bottom relief of the sea determine the most important aspects of its oceanographical regime: the water exchange with the Barents Sea, a highly pronounced effect of river runoff, the formation of water masses and frontal zones, the water circulation structure, the regular features of the tidal wave propagation, and the ice regime. Therefore, it is very important, from the point of view of modeling the White Sea s oceanographical regime and ecosystem, to establish an accurate digital model of the bottom relief. This required development of a new, original digital model of the bottom relief, with a very high spatial resolution, a 1-minute latitudinal step ("'1.7 km), and a 2-minute longitudinal one ("'1.5km), based upon the updated and most comprehensive bathymetric data. This problem has been solved by the Nansen International Environmental Research and Scientific Centre (NIERSC), St. Petersburg, Russia, in cooperation with the TRANSAS company (TRANsport SAfety Systems, Electronic Technologies), St. Petersburg, using a special software package developed for processing bathymetric data from sea navigation electronic maps at the scale 1:5,000-1:200,000. This has been developed by the TRANSAS Company and the Main Administration of Navigation and Oceanography of the Ministry of Defense of the Russian Federation (GUNIO).

In the development of a digital model of the White Sea bottom relief, inter- polation technology was used, taking account of the irregular geometry of the White Sea region - the presence of numerous islands and the incised shoreline. To calculate depths, at the nodes of a regular grid, a simple calculational interpolation scheme was employed using the method of triangulation with a linear interpolation of discrete values of depths and linear values of map isobaths. The program to calculate the depth at a node of a regular grid involved the following logical procedures:

• Search around the grid node within a radius multiple to the grid step for at least three nearest depth marks (and/or isobath line tops) on the largest scale map for subsequent interpolation of the depth to the node location.

• Additional loading of smaller scale maps in the case of a lack of data.

• Analysis of the presence of obstacles on the map (land, dangerous depths, shallows, banks, etc.) between the depths that are subject to interpolation, and the culling of such depth marks via ascribing them a zero value in the case of land or islands, or by the relevant depth value in the case of shallows or banks.

• Accounting for the weighting coefficient of the depth mark values (isobath line tops) in inverse proportion to the square of the distance from the grid node to the depth mark (isobath), in the cases when the selected initial depth marks exceed the limits of the basic search range, equal to a single step of a regular grid.

• Estimation of the precise magnitudes of depths and isobaths within the radius of a single grid step, and their adoption for the calculation of the interpolated values at the grid node.

Provided there was a great number of depth measurement points, this rather simple and clear method yielded the best results. The initially obtained model of the relief was verified according to the best-pronounced features of the bottom relief; as a result, for some regions, a repeated interpolation was accomplished, using the most detailed initial maps. Since then a final version has been developed. It was incorpo- rated into a dedicated integrated Geographic Information System (GIS) for the White Sea region (Kaitala, Shavykin, and Volkov, 2002) - see also Chapter 8.

For comparison, IBCAO data with a 2.5-km grid-cell resolution were used (Jakobsson and Cherkis, 2001). The results of the comparison are shown in Figure 1.2 (see color section). The TRANSAS/NIERSC bathymetry model exhibits more detail and the depth distribution histogram is more realistic than that of the IBCAO bathymetry model. Indeed, Figure 1.2 clearly indicates the TRANSAS/NIERSC map has considerably more detail on the characteristic features of the White Sea relief (The White Sea, 1985). The ridge relief of Voronka is shown distinctly. It can be seen that the shallow Mezenskiy Bay has a highly complicated bottom relief, which actually is a vast shallow-water area with a narrow axis at the continuation of the Mezen River mouth. The Kandalaksha Depression structure, subdivided into several separate depressions, is expressed in more detail on the TRANSAS/NIERSC map.

Thus, the obtained digital model of the White Sea bathymetry is the most precise one, and was used for the numerical simulation of the changes occurring in the oceanographic regime and ecological state of the White Sea.

1.3 PHYSICAL GEOGRAPHY OF THE WATERSHED

The White Sea and its basin are part of the Eastern European geologic platform, found in the north-eastern part of the Baltic Shield and Russian Platform. Due to a variety of geologic and tectonic processes which occurred in the past, the White Sea bottom presently encompases a variety of morphological structures. Within the watershed boundaries, there are sole plains and plains built of horizontal strata, as well as block mountains. The basin of the White Sea is formed due to faults. The eastern part of the Baltic Shield has originated in Archaean and early middle Proterozoic. During the early Proterozoic, the Archaean basement split into several blocks (i.e., Karelian, Kola, White Sea, and Murmansk). The north-western crystal- lic horst is bounded by transversal and lengthwise faults. The largest part of the White Sea is located within the boundaries of the White Sea Block. The remaining areas are part of the Baikal folding deposit of the Timan system. These slabs are rather mobile structures and their movement is related to the isoglacial relief formed after the melting of ice sheets. The entire eastern part of the White Sea (i.e., the coastal areas from Kanin Nos Cape to the estuary of Severnaya Dvina, and coastal

areas of the Onega Bay and eastern part of the Kola Peninsula) is gradually deepening. The maximum depression is recorded in the Dvinskiy Bay and the Gorlo (13 m during the postglacial period). The isostatic elevation is a feature of the northern part of the sea (Kovda - 4.5mm per year). Due to block morphology of the Baltic Shield crust, the rate of its elevation is decreasing from central areas to the periphery. Seismic activity, known in the Kandalakshskiy Bay, is also related to the block movements recorded in this area.

The total area of the White Sea watershed is about 715,000 km2. It spans more

than 1,000 km from north to south and about 900 km from west to east. The significant part of the sea is found beyond the Arctic Circle. Several biogeographic zones, from tundra to southern taiga, are found in the White Sea region. As a result, the area is subject to diversity of natural habitats and climatic conditions. The physical geography and climatic conditions for each sub-region are summarized in Section 1.4 - see Chapter 3 for an analysis of climatic variability and change.

1.4 PHYSICAL GEOGRAPHY OF THE ADMINISTRATIVE UNITS

Below, we provide a brief physical and geographic characterization of the main administrative units found within the limits of the White Sea watershed. The surface area and population data for the units are shown in Table 1.1.

The White Sea watershed incorporates certain areas of five Russian adminis- trative units - Arkhangelsk Oblast, Murmansk Oblast, Vologda Oblast, the

Table 1.1. Area and population of units in the White Sea watershed.

watershed

Figure 1.3. Boundaries of the administrative divisions (oblasts and republics) in the White Sea catchment (indicated by a dotted line).

Republic of Karelia, and the Republic of Komi. In addition, it includes some small parts of the Kirov, Perm, and Kostroma Oblasts, Nenets Autonomous Okrug, and Finland (Figure 1.3).

The administrative units can be subdivided into three groups, based on their influence on the White Sea ecosystem:

1 Areas adjacent to the White Sea and consequently exerting the maximum impact on its ecosystem (Republic of Karelia and the Murmansk and Arkhangelsk Oblasts).

2 Areas not bordering the White Sea but, nevertheless, important in their impact (Republic of Komi and Vologda Oblast).

3 Small areas located far from the White Sea and having practically no effects on the marine ecosystem (the remaining administrative units).

The emphasis here is on the administrative units of the first group in the above list, to which separate sections are devoted. The second group will be characterized only briefly and the third group will not be considered here.

1.4.1 Arkhangelsk Oblast1

The Arkhangelsk Oblast is located in the far north of the European part of Russia. To the north, the region is bordered by the Barents, Pechora, and Kara Seas, and to the west by the White Sea. The coastline is about 3,000 km long. The region borders the Republic of Komi in the east, the Republic of Karelia in the west, and Vologda and Kirov Oblasts in the south. The Arkhangelsk Oblast incorporates such large islands as Novaya Zemlya, Vaigatch, Kolguev, Solovetzkie Islands, and a number of smaller islands. The Nenets Autonomous Okrug (total area 176,700 km2, population 46,000) is also part of the oblast.

The total area of the Arkhangelsk Oblast is 410,700 km2. It is located between

60o38tand 81o52tN and 35o52tand 65o40tE. The maximum distance from south- west to north-east is 1,545 km. Practically the entire region is part of the White Sea basin, occupying almost half of its area. The Nenets Autonomous Okrug belongs principally to basins of other Arctic seas. The oblast is located in the northern part of the Eastern European plain. The geology of the region is characterized by the predominance of platform structures and a deep crystalline base rock of the Archaean and Proterozoic age, overlain with a thick (dozens or even hundreds of meters) layer of sediments (in contrast to Karelia and the Kola Peninsula). Regard- less of deep-lying base rocks, their boulder structure and fractures determine the morphology of valleys and plateaus, as well as the direction of the main rivers. The base rocks are composed of gneiss, granite, strongly metamorphosed shale, quartzites, etc. The base rocks are covered with glacial and postglacial deposits (mainly boulders and clay deposits of the glacial moraines). In addition, sandstone-clay deposits from marine transgressions or of palaeo-lacustrine and glacio-fluvial origin are found over the flats. Sediment deposits are composed of easily eroded rocks - limestone, gypsum, dolomites, and marlstone - found close to the surface. Such morphology is closely related to the karst phenomenon, found in some areas of the region. This phenomenon is seen in the development of particular relief features (funnels or craters), strongly influencing the hydrological regime of surface and subterranean water.

The Arkhangelsk Oblast is characterized mostly by a flat landscape with a general slope towards the north. This monotonous relief is occasionally interrupted by small mountain ridges: the strongly eroded Vetrenii Poyas, Timan ridge, Kanin Kamen and Pai-Khoi, with maximum recorded elevations of 250-470 m. The most characteristic features of the landscape are moraine hills and ridges and karst and lacustrine depressions. The central part of the region is the Onego-Dvinsk-Mezen plain, inter- rupted by the wide network of various depressions, occupied by river plains. The coastal areas are strongly swampy depressions, composed of deposits of various origins. The Nenets Autonomous Okrug occupies a part of the Pechora plain.

The principal features of the climate are governed by the predominantly westward airflow, with frequent intrusions of the cold Arctic air masses and

1 Source: Surface Water Resources of the USSR (Vol. 2) (1972) Karelia and North-Western Region. Part 1. Hydrometeoizdat, Leningrad, 528pp. (in Russian).

strong influence of the adjacent Arctic seas (see Chapter 3). The incoming Atlantic cyclones are accompanied by the frequent changes in air masses causing the cloudy, cold summer and warm winter with frequent warm-up periods. The intrusion of the Arctic and Siberian air masses is in line with the cold and dry winds and sudden freezing conditions. In general, the area s climate is characterized by a short and cool summer, prolonged cold winter with stable snow cover and frequent blizzards, and generally unstable weather conditions during the entire year. Coastal areas are characterized by cooler summers and milder winters. The winter lasts 5-6 months in the south-western regions and 6-7 months in the north-east, with a summer period duration of 3-4 months and 1-2 months respectively. Average annual air tempera- ture follows the same trends, from 3o to -8o. January is usually the coldest month (February in coastal areas), with average temperatures from -11 to -20o. July is the warmest month, with predominant temperatures between 4-17o.

Arkhangelsk Oblast is located within the zone of excessive humidity. The average annual precipitation increases from the north-east to south-east from 550-800 mm. The principal part of precipitation falls during the warm season (65-70%). Average annual relative humidity increases to the north-east from 77-80% to 82-86%. Southerly and south-westerly winds predominate during wintertime, with northerly and north-easterly winds prevailing in summer. Mean annual wind speed is 7-8 m sec-1in coastal areas and 2.5-5 m s-1near the southern borders.

The three principal biotopes of the region are tundra, northern, and middle taiga. Coniferous forests prevail over the majority of the territory. These forests are composed mainly of fir trees with some areas covered by birches, pines, and aspen. There are also pine forests, situated mainly along the riverbanks. North to the Arctic Circle, the vegetation is represented by forest-tundra, mosses, and lichens intermittent with various types of shrubs. Forest cover of drainage regions in the taiga zone is mainly more than 80% (occasionally reaching 95-99%), with water- logged areas, constituting 5-10%, being higher in northern regions.

The river network is well developed and relatively uniform over the entire area. The density of the river network is about 0.5-0.6 km per km2, decreasing to 0.1-0.2 km per km2 and even less in karst regions. Small rivers and creeks with lengths less than 25km are predominant. The total number of such small rivers and creeks is about 50,000, with a total length reaching almost 100,000 km. The principal rivers are the Pechora (length 1,809 km, average annual discharge 139 km3), Severnaya (Northern) Dvina (744 km, 110 km3), Mezen (966 km,

29.0 km3), and Onega (416 km, 16.8 km3). The three latter rivers are the principal

tributaries of the White Sea, contributing to the main portion of the river discharge to the sea. (The Pechora discharges rather more into the Barents Sea.) The Pechora and Severnaya Dvina are the largest water-navigation routes in the European part of Russia, being respectively the second and fourth by water discharge. The Pechora and Severnaya Dvina transport large quantities of sediments to the sea and also develop vast tributary networks in river deltas. The Onega and Mezen Rivers are characterized by broad, shallow estuaries.

The lakes in the Arkhangelsk region are mainly small (less than 0.5km2), with

Peat bogs occupy about 6% of the entire territory, rather unevenly distributed. The most waterlogged areas are found in the coastal regions of the White and Barents Seas.

1.4.2 The Murmansk Oblast2

The Murmansk Oblast is located on one of the largest peninsulas of Russia - the Kola Peninsula. The region is surrounded by the Barents and White Seas to the north, east, and south. It shares a common border with Norway and Finland in the west and with the Republic of Karelia in the south. The region spans from about 400 km from north to south (from 70o-66oN) and more than 500 km from west to east (from 28o-41oE). Except for the southernmost areas, the entire region is located north of the Arctic Circle. The total area of the region is 144,900 km2. The region is a part of the basins of two seas: the White Sea (53% of the territory) and Barents Sea (47%).

The Kola Peninsula is located in the eastern part of the Baltic (Fennoscandian) shield, composed of very ancient crystalline rocks of Archaean and Proterozoic age and overlain with a thin layer of loose Quaternary deposits. Crystalline rocks are represented by metamorphic and effusive complexes, with significant (mainly granite) intrusions. Archaean granite-gneiss rocks predominate. The Quaternary deposits are represented by the complex of Ice Age formations of upper Quaternary age (moraine, sandy aquatic/glacial deposits, etc.) and post-Ice-Age formations (e.g., peat, sand-clay marine, and lake deposits).

The Kola Peninsula is characterized by its relatively diverse and rough relief. Its main features (large elevations and large lakes basins) have developed during the most recent Ice Age. However, the continental ice sheets and, partially, post-glacial processes have significantly smoothed the roughness of the landscape. Thus, the principal relief-forming factors of the Kola Peninsula became the tectonic processes, denudation, and the erosion-accumulative activity of the ice sheets and melting water. The Kola Peninsula can be subdivided orographically into three provinces: western, north-eastern, and south-eastern.

The western province (to the meridian of the Voronya-Umba Rivers) is characterized by mountainous landscape with elevations of more than 1,000 m. Found here are all of the principal mountains of the region with elevations up to 1,000-1,200 m: Khibiny and Lovozersk Massifs, Salnie, Volchii, Monche, Chuna, and other tundra areas. The mountains are interrupted by deep depressions occupied by lakes and swamps.

2 Source: Surface Water Resources of the USSR (Vol. 1) (1970) Kola Peninsula. Hydrometeoizdat, Leningrad, 316 pp. (in Russian).

The north-eastern province is delimited in the south by the Bolshie Keivi ridge. This province is characterized by an undulating landscape with relative elevations reaching 150-250 m, and numerous lakes.

The south-eastern province (to the south of the Bolshie Keivi ridge) exhibits a basically flat countryside with an amplitude of relative elevations of 20-50 m. The absolute elevations are mostly less than 200 m, though a few mountains reach above 300 m. This province slopes slightly toward the White Sea. The coastal areas commonly have terraces. The south-eastern part of the province is characterized by the variety of glacial types of relief.

The climate of the Kola Peninsula is subject to the moderating influence of the surrounding seas and especially the northern extension of the Gulf Stream-trans- Atlantic drift system. The characteristic feature of the climate is a cool and rainy summer and a relatively warm winter, and unstable and suddenly changing weather, caused by frequent changes in air masses, movement of cyclones, and fronts. The annual input of solar radiation ranges from 55-60 kcal cm-2in the north to 70 kcal cm-2in the south. The average annual air temperature is +1oC in the coastal area, -1 to -2oC in remote flat regions, and -3 to -4oC in the mountains. The coldest months are January and February (average monthly tem- perature -7 to -9oC on the coast of Barents Sea and -10 to -15oC over the remaining territory). July and August are the warmest months (mean monthly temperature changes depending on the particular region from 9-14oC). The Kola Peninsula is a region of excessive precipitation and moderate evaporation. The annual precipitation for the majority of territories is 550-600 mm, with about 60% of it falling during the warm season. The atmospheric precipitation is unevenly distributed, especially in the mountains. The average annual relative humidity is about 80%. The winter is characterized by the polar night (e.g., in Murmansk from 1 December to 13 January), while the summer is characterized by the midnight sun (from 23 May to 21 July).

It should be noted that climatic zonation is known for mountains, with lower air temperature, increased precipitation and wind strength, and prolonged snow cover with an increase in elevation. Two geobotanical zones are known for the Kola Peninsula - tundra (occupying about 20% of all territory) and taiga (60%) - as well as a small transitional zone, the forest-tundra (20%). Elevations in the taiga zone are mainly mountain tundra. The woods are those of fir, pine, and birch. The areas of pine and fir regions are of about equal size, but fir is mainly known from the east, while pine forest is characteristics of the western and southern areas. The so- called forest-tundra is composed of sparsely grown birch trees. The swamps cover about 20% of the Peninsula territory and meadow vegetation is known in very small areas.

The hydrological structure of the Kola Peninsula is well developed and is dis- tributed approximately equally between the basins of the Barents and White Seas. Rivers are characterized by weakly developed valleys and channels and a large number of rapids and waterfalls. All rivers can be subdivided into three types: mountain, semi-flat, and lacustrine (lake-river) systems. In total, the region boasts 20,600 rivers with a whole length of 37,000 km. However, 95% of these are very

small rivers (less than 10 km). These small rivers sum up to 61% of the total river length. There are only 15 rivers whose length exceeds 100 km. The rivers Ponoi, which with its length of 426 km is the longest river of the Peninsula, Varzuga and Umba are the main tributaries of the White Sea. The Tuloma, Pechenga and Voronya rivers belong to the Barents Sea basin.

The lakes of the Kola Peninsula by their origin can be subdivided into glacial and tectonic, with the predominance of the former. These are for the most part shallow lakes. In total, the region hosts 107,000 lakes with total area 8,200 km2. However, 99.2% of these lakes are less than 1 km2, covering 36.6% of the entire lake area. Only 835 lakes are larger than 1 km2, of which only 4 are larger than 100 km2. The principal lakes of the Peninsula - Imandra, Notozero, Umbozero, Lovozero - are of tectonic origin and thus are characterized by a greater depth, elongated shape and complex coastline.

1.4.3 Republic of Karelia3

The Republic of Karelia is located in the north-western part of the European part of Russia, between 61o and 67oN (distance N-S is "' 650 km) and between 30o and 38oE (maximum E-W distance is "' 400 km). The total area of the republic, including Karelian parts of the Ladoga and Onega Lakes is 172,400 km2- without these areas it is 155,900 km2. From the north-east, the republic is limited by the White Sea, from south and south-east by Ladoga and Onega Lakes. It is bordered by the Murmansk Oblast in the north, Arkhangelsk Oblast in the east, and the Vologda and Leningrad Oblasts in the south.

Geologically, Karelia is the eastern outskirt of the Baltic (Fennoscandian) shield - the region of the most ancient crystalline rocks of Archaean-Proterozoic origin. These rocks are covered by complex glacial (primarily), interglacial, and postglacial deposits, whose thickness ranges from 0 to 110-130 m, with maximum thickness in the southernmost part.

The principal elements of relief are a combination of very ancient tectonic processes and denudation and accumulation of the Quaternary period, the principal features of which were strong continental glaciers. The last of these glaciations - Valdai, which terminated only 10-11 thousand years ago - has played a major role in shaping the modern landscape. Glacial movement from Scandinavia has transferred and deposited huge quantities of unsorted rocks (moraines). This resulted in a unique, extremely rough ridge-slope landscape with absolute elevations not exceeding 200 m. Elevations approaching 600 m (Nuorunen Mountain, 577 m) are found only in the north-westernmost part of the republic. Glacial and glacio-fluvial activities have reshaped the pre-glacial relief, without changing its principal features. In particular, the results of vertical tectonic movement, accompanied by elevations and sinking of the earth s crust, can be

3 Source: Surface Water Resources of the USSR (Vol. 2) (1972) Karelia and North-Western Region. Part 1. Hydrometeoizdat, Leningrad, 528 pp. (in Russian).

clearly seen. This was the time when the basins of Ladoga, Onega, and other lakes, as well as the basin of the White Sea, were formed and fractures and crevices facilitated the formation of river valleys.

Karelia s climate is temperate continental with some features of the marine influence. The climate is characterized by mild winters, short, cool summers, significant cloud cover, and unstable weather conditions during the entire year. The average air temperature ranges from 0oC in the north to 3oC in the south. January is the coldest month (-12 to -13oC in the northern part, -9 to -10oC in the south). Freezing temperatures up -50oC are recorded once in every 80-100 years. July is the warmest month (14-15oC in the north and 16-17oC over the remaining territory). The maximum temperature recorded is 36oC.

The Republic of Karelia belongs to the zone of excessive humidity, its dampness due to relatively little incoming heat and well-developed cyclonic activity during all seasons. The precipitation is 500-750 mm per year, increasing from north to south. At the same time, due to low summer temperatures, an excess of clouds, and increased air humidity, Karelia is a region of relatively small evaporation, ranging from 310 mm in the north to 420 mm in the southern areas.

As a result of a cumulative influence of all factors listed, there is a well- developed drainage system, which belongs to the basins of the White Sea and Baltic Sea. About 57% of the republic s territory is part of the White Sea basin and 43% (excluding Ladoga and Onega Lakes) falls within the Baltic Sea basin. The watershed is primarily composed of small rivers or short creeks, interconnecting numerous lakes and forming lake-river systems.

According to modern data, the total number of rivers (including the Karelian isthmus) is 26,700. The total river length is 83,000 km. Rivers with length less than 10 km are predominant. The total number of such rivers is 25,300 (95%) with a total length of 52,300 km (63%). Only 30 rivers are longer than 100 km and are listed as

average rivers. The density of the river network is 0.53 km per km2. The drainage

area is also small for the majority of rivers. Only 366 rivers have drainage areas greater than 100 km2, including 51 with drainage areas exceeding 1,000 km2and 5 with drainage areas greater than 10,000 km2(the Kem, Vyg, Kovda, Vodla, and Shuya Rivers).

Small river depths, weakly developed river valleys, and stepped longitudinal profile seen as repeated rapids intermittent with river reaches - all these features are explained by the relatively young age of the Karelian rivers and basic features of the crystallic bedrock. In addition, narrow and low watersheds and the proximity of adjacent river systems are also characteristic features of the Karelian hydrology. Such hydrologic patterns facilitate the diversion of runoff to other areas (Suna River-Palie Lake, Pongoma River - Topozero Lake). A complex rugged relief between numerous lakes often facilitates the simultaneous runoff into several directions: Engozero Lake-Kalga and Vonga Rivers; Sariyarvi Lake-Loimolanioki (Tulemaioki) and Pensanioki (Uksunioki) Rivers; and Segezhskoe Lake - Obzhanka and Segezha (tributary of the Svir River) Rivers.

The principal structural elements of the hydrological network of Karelia are various water bodies (lakes and water reservoirs), mainly determining the main

features of the republic s watershed. Overall, there are 61,100 lakes with total area about 18,000 km2in Karelia. Moreover, about 50% of Lake Ladoga and 80% of Lake Onega - the largest freshwater lakes in Europe - are found within the republic s boundaries. About 12% of the republic s territory is covered with lakes, with this figure reaching 21% if one considers the Karelian parts of the Ladoga and Onega Lakes - this parameter is one of the highest in the world.

Lakes with surface area less that 1 km2form the greatest proportion, with only 1,389 (2%) water bodies greater than 1 km2, and of these only 20 lakes exceed 100 km2. Lakes without visible runoff (local term lamba ), mainly located in the woods and peat bogs, are predominant among the small water bodies.

Two main types of lake basins can be defined by origin: tectonic and glacial. Nearly all large and medium-sized water bodies are of tectonic origin. Their basins are located within fractures and faults marked with clear indications of glacial erosion. As a rule, they possess complex coastal landscapes, rugged bottom relief, and great depths. Glacial lakes are found in depressions between the moraine ridges and hills. These lakes are small in size and have a less jagged, often rounded shape and a flat bottom without great differences in depth (not usually exceeding 5-10 m). In addition, there are narrow, long lakes crossed by rivers and there are numerous peat bog lakes.

One form of economic use of water resources is to regulate the river runoff by developing water reservoirs. The principal reservoir type is hollow (lake-like), created in almost all large lakes. The predominance of lake-like reservoirs over valley reservoirs is a characteristic feature of Karelia.

The total volume of water accumulated in the water reservoirs is 80.2 km3. Of these, the total useful carrying volume is 18.6 km3, allowing regulation of 47% of the annual river discharge. Yet another 65.0 km3of water is found in natural lakes. In

addition, large water volumes from Lake Onega (Verkhne-Svirskoe water reservoir) and Lake Ladoga should be added to these figures. The main portion of water, contained in various water bodies (78%), is found within the watershed of the White Sea, where they are mainly represented by water from the reservoirs. About 90% of the total useful carrying capacity of water reservoirs and 63% of the river runoff is found here. In contrast, the waters of the Baltic Sea basin are mainly concentrated in the lakes, as the runoff is less regulated and rivers carry smaller volumes of water.

The mean annual discharge of Karelian rivers is 57 km3, of which about

49.7 km3is formed over the Karelian territory (the so called local discharge ). The remaining part of the discharge (13%) is from adjacent regions (mainly from Finland and the Arkhangelsk Oblast). About 55% of the republic s river discharge enters the White Sea, while 25% enters Lake Onega and 20% enters Lake Ladoga.

The Republic of Karelia is found within the northern (two-thirds of the repub- lic s territory) and middle sub-zones of taiga. Forest areas cover more than 50% of the total area, peat bogs more than 20%, occupying about 30% together with water- logged forests. About 400 species of trees and shrubs are known in Karelia. Principal timber species of the Karelian woods are common pine, European or Siberian firs,

and certain species of birches, aspen, and alder. Conifer woods occupy about 90% of the total forest area. The northern sub-zone is dominated by pine forests, whereas the middle sub-zone is mainly covered with fir. More than 90% of the deciduous forests are composed of birch.

Date: 2016-03-03; view: 594