Boundaries

In the north the ecoregion includes the Chernaya, Sestra, and Okhta rivers, as well as the entire Neva River drainage just downstream from its source at Lake Ladoga. The ecoregion also includes the Volkhov River, which connects Lake Ladoga [ecoregion 409] with the Central and Western Europe ecoregion [404]. In the south the border follows the main divide between the river drainages that  flow into the Baltic Sea and North Sea, and rivers flowing to the south. In the west the border runs along the eastern margin of the Neman [Nemunas = Nyoman] River watershed (Neman River exclusive).

Topography

This lowland ecoregion lies on the Eastern European Plain with elevations that average around 100 m, but range from sea level to 313 m asl in the Valdai Hills (Hijmans et al. 2004). River valleys were formed after the glacial retreat 10-11 kyrs BP, which left depressions in the landscape and glacial deposits in the form of moraines. The bedrock consists of crystalline basement in the Western Dvina; Vendian, Cambrian, Ordovician, and Devonian rocks in the Narva; and limestones in the Valdai Hills (Timm et al. 2009).

Freshwater habitats

The Neva River rises in Lake Ladoga, flows through a valley called the Neva Lowland, and empties into the Neva Bay of the Gulf of Finland. Near the estuary its arms and anabranches form a wide delta. The Neva River is connected with the Volga River and the White Sea by a system of artificial canals.

The total slope of the Neva River is small, approximately 5 m, and its mean gradient is equal to 0.07‰. The bottom of the river channel throughout its flow is situated below the level of the Gulf of Finland. The main left bank tributaries of the Neva River are the rivers Tosna and Izhora; the Okhta River is a right bank tributary. As compared to other large rivers, the length of the Neva River is small (only 74 km), and its depth along the channel  reaches 8—11 m. Throughout the year the Neva River flows fully, with an average intensity of flow equal to 2600 m³/s. The Neva River has practically no floodplain; its coasts are generally high. The width of the Neva River is approximately 500 m, and in some areas, up to 1 km and more. The catchment area of the river is densely populated.

The Neva River drainage is triangular in shape. Its base is directed northward, stretching from the northernmost tributaries of the Vuoksa River (Finland) drainage up to the upper reaches of the Ileksa River (Arkhangelsk Region). The apex of the river drainage is situated in the southern part near the source of the Lovat’ River (flowing out of Lake Lovatets, Belarus). The maximum extent of the drainage from west to east is approximately 600 km, from south to north is 1100 km. Thus, the Neva River drainage is situated within three states, and in Russia encompasses seven subjects of the Russian Federation.

The total area of the Neva River drainage is 281,600 km². The drainage is divided in the following parts: Svir’ – Onega has an area of 83,200 km², which is 29.5% of the total drainage area; Volkhov – Il’men’ has an area of 80,200 km² (28.5%); Vuoksa – Saimen has an area of 66,700 km², including an area of 52,300 km² in Finland (23.7%); a catchment area of Lake Ladoga 46,500 km² (16.5%); and a catchment area of the Neva River, 5000 km² (1.8%). In the west the Neva River drainage is closed by the Neva Bay and the eastern part of the Gulf of Finland.

A large number of lakes are situated in the Neva River drainage, including great European lakes as Ladoga and Onega (in ecoregion 409), Il’men’, Saima, and a number of other large lakes with areas greater than 200 km² each. There are also tens of thousands of large (up to 200 km²), medium, and small lakes within the Neva River drainage.

The Neva River drainage is fed mostly by snowmelt. The water level of the Neva River, regulated by Lake Ladoga, rises slightly during the spring snowmelt. The abrupt fluctuations of water level in the lower reaches are usually determined by winds, and also by ice jams during the period of freeze. In autumn water set-up from the Gulf of Finland is sometimes accompanied by strong floods.

The drainage of the Zapadnaya Dvina River occupies an area of 84,440 km². Its lower part is situated in swampy lowland, whereas the upper and middle parts flow along a terrain with a typical lake moraine landscape. Numerous lakes of glacial origin are scattered throughout the lowlands between moraine ridges and hills. In the northeastern and eastern parts of the drainage are the Valdai Hills, which form the watershed for the Zapadnaya Dvina, Volga, and Dnieper drainages. The Zapadnaya Dvina (Daugava) River rises in Lake Dvinets in the Valdai Hills, 14 km from the riverhead of the Volga River. The upper reaches of the river (300 km) lie in Russia, the middle reaches (350 km) in Belarus, and the lower reaches (355 km) in Latvia, where it is called Daugava. It flows into the Gulf of Riga of the Baltic Sea. The major tributaries in the Belarus part of the Zapadnaya Dvina are: left bank tributaries, Disna (188 km), Ushacha (118 km), Ulla (117 km), Luchesa (100 km), Kasplya (139 km); right bank tributaries, Drissa (172 km), Obol (169 km), Usvyacha (134 km).

The water level of the Zapadnaya Dvina fluctuates notably, reaching 10—12 m above its low level in spring. A maximum is observed in late March through early April. During the October – November autumn floods, the water horizon rises up to 3—4 m. The lower river’s channel width ranges from 370-750 m, and its depth varies from 5-15 m. This area is fringed by extensive floodplains that extend 3-4 km with numerous oxbow lakes. Extensive flooding occurs during spring, with peaks that can reach 2000 m/s³ in late March and early April. Snowmelt contributes roughly half of the total annual discharge in the Western Dvina, 1/3 of the total annual discharge of the Narva, and around ½ of the discharge of the Volhov (Timm et al. 2009).  Groundwater and rain comprise the remaining volume.

The Narva is 650 km long and 56,000 km² in area, with an annual discharge of 400 m/s³. It is split into two parts by Lake Peipsi into the Velikaja River north of the lake and the Narva proper south of the lake. The Narva is connected to the Luga River via the Rosson River. The Luga is 358 km long and 14000 km² in catchment area. It discharges into the Luga Bay in the Gulf of Finland (Timm et al. 2009).

Lake Peipsi is the fourth largest lake and largest hardwater eutrophic lake in Europe (Timm et al. 2009). It has an average depth of 7 m and maximum depth of 15 m. It is flanked by swamps, including the Ramsar site Emajõe Suursoo mire (IUCN 1993). The flat topography supports a number of wetlands, most notably in Estonia and Latvia. Peatlands, raised bogs, fens, and mire complexes are common, as well as swamp fens, wooded swamp fens, and wet forests. In addition to Emajõe Suursoo, other Ramsar sites include Teici and Pelecare, Berezovye Islands, Mshinskaye wetland, Soomaa National Park, Lubana wetland, Osveiski, Ziemelu purvi, Nigula, Matsalu Bay, Muraka, and Puhto-Laelatu-Nehatu Wetland Complex (Wetlands International 2002).

The Venta River rises on Mount Zhemaitskaya in Lithuania. Downstream from the town of Uzhventis it flows among swampy meadows and forests, sometimes forming wider areas with slightly noticeable flow. The Venta River flows through a relatively narrow valley, in some areas cutting into ledge rocks that rise high above the river in the form of dolomitic rocks. The width of the river channel fluctuates from 15 m in the upper reaches of the river up to 150 km in the lower reaches. The length of the river is 300 km. The hydrological regime of the Venta River is characterized by a number of peculiar features. Under the impact of warm air masses that move from the sea, floods sometimes occur in winter. Spring floods on the Venta River begin earlier than on other rivers.

Terrestrial habitats

Apart from lakes and rivers in the drainage of the Neva River, swamps are widespread, occupying a large part of the area. The catchment area of the Duagava River is situated in an extensive lake region. The upper parts of the drainages of the main tributaries are characterized by flat relief, and also abound in swamps and lakes. A large number of lakes are situated in the upper part of the drainage in Russia and Belarus. Numerous lakes are characteristic of the Druika, Drisvyata, Svolna, Turovlyanka, Lukomka-Yugna, and Drissa catchment areas.

A majority of the area lies within the Sarmatic mixed forests [PA0436], bordered by the Scandinavian and Russian taiga [PA0608] to the north (WWF 2001).  Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) are the dominant trees mixed with deciduous species like pedunculate oak (Quercus ruber), silver birch (Betula pendula), and aspen (Populus tremula). Meadows, floodplains, and bogs are significant features of the landscape (Timm et al. 2009).

Description of endemic fishes

Coregonus maraenoides is the only whitefish species distributed in the Chudskoye-Pskovskoye [Peipsi-Pihkva] Lake basin. It was a very important commercial fish that attained a size up to 600 mm SL. It was widely used for translocations in the former USSR, Poland, Germany, in many lakes in the Utals region of Russia, Lake Sevan (Armenia), and in Lake Balkash (Kazakhstan). It feeds mostly on dwarf smelt (Osmerus eperlanus spirinchus). Juveniles eat insect larvae, fish eggs, and crustaceans. The main spawning places are in the southern coastal part of Lake Chudskoe. It also enters some rivers for spawning. It spawns under ice during the period between October-December, with a peak in late November. Its embrionic development lasts about five months. It is highly threatened in Russia, and records are rare.

Justification for delineation

This ecoregion was delimited based on the early age of the hydrographic bodies and their fish fauna within the ecoregion, as well as the unique mixed composition of the fish fauna. The ecoregion is clearly delimited from the Central and Western Europe ecoregion [404] by the absence of species that are common in drainages of the latter ecoregion (e.g. Neman, Vistula, Oder, Rhine, etc.), as well as the Dnieper and Dniester drainages (Eudontomyzon mariae, Barbus barbus, Barbus petenyi, Barbus waleckii, Romanogobio belingi, Romanogobio kesslerii, Sabanejewia baltica and others). The Neman and Vistula rivers, as well as other river systems in the west, demonstrate clear affinities based on exchanges of faunas due to river captures that took place during the Pleistocene.

Level of taxonomic exploration

Fair