Hydrology

The Narva River is the largest river in Estonia; two-thirds of its catchment area is located in the territory of Russia. Compared to other rivers in Estonia, it is also the river with the largest water volume. The Narva River is 77 km long; of this about 30 km has been dammed at Narva Water Reservoir. Due to a good natural regulation of water flow by Lake Peipsi, extensive floods practically never occur in the area and the lake also keeps the Narva River from drying out. The average discharge at the mouth is 370 m³/s. Until 1957, i.e. before the construction of a hydroelectric power station, the Narva River was famous for its magnificent waterfall. Later the riverbed at the waterfall dried out. The river is navigable from its mouth up to the town of Narva and from Lake Peipsi downstream. The stretch of river in between cannot be navigated since the river descends more than 20 m from the waterfall terrace.

Lake Peipsi is the fifth largest lake in Europe with a total area of 3555 square km. The lake actually consists of three parts: Lake Peipsi (2610 square km), Lake Pihkva (710 square km), and narrow (the width at the narrowest point is 3 km) and deep Lake Lämmijärv (235 square km) which connects the two above-mentioned lakes. Here the lake is the deepest (maximum depth 15.3 m). 1570 square km (44%) of the water area of Lake Peipsi is located in the territory of Estonia. The water-containing capacity of the lake reaches up to 25 km3, which exceeds by a factor of two the annual runoff of rivers from the territory of Estonia.

In spring, after the snow melts, the water table in Lake Peipsi rises nearly a metre. The rise of the water table causes the flooding of the lower shore areas of the lake. During the periods when the water table is at its highest, the total area of Lake Peipsi may increase by about 780 square km. The water table in the lake is the lowest in October. This is due to the fact that in summer evaporation from the water surface is intensive and water inflow into the lake is the smallest. Later, water inflow into the lake starts to increase due to autumn rains. Fluctuations of the water table differ from year to year and also depend on alteration of dry and wet periods. About thirty-year cycles of such periods are most clearly distinguishable.

Ice cover on Lake Peipsi forms at the end of November, in mild winters even later. Ice cover is the thickest (average 50–60 cm) by the second half of March. Due to currents and wind, cracks that can be several metres wide appear in the ice cover. These cracks may partly freeze over during severe frosts. Later, low ice hammocks form in such places. During the period of ice breaking, significant quantities of ice may be driven ashore by strong winds and may cause severe damage in the coastal zone.

Vendace and sparling
Fish stock in Lake Peipsi is abundant. It is deemed to be one of the best fishing lakes in Europe. The average annual catch is approximately 10 000 tonnes; thus, the productivity of the lake is about 30 kg/ha. Commercial fish species include vendace, sparling, pike, pikeperch, perch, bream, etc. Catch varies from year to year, depending on the natural conditions and fishing load. Ice fishing is very popular: in winter, several thousand anglers can be seen on Lake Peipsi during some weekends.

Lake Peipsi and the Narva River are transboundary water bodies. Thus, the issues related to their use and protection can be resolved only in compliance with international agreements and must be based on good will. As the Republic of Estonia and the Russian Federation are both interested in preserving Lake Peipsi as a valuable fish lake, one of the first agreements concluded between these two parties regulated the use of the fish stock of Lake Peipsi.

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