Water-ecological resources of Republic of Karelia. Introduction

Karelia has a well-developed drainage network comprised of 23,600 rivers and 61,000 lakes including the largest lakes of Europe - Onego and Ladoga, as well as the White Sea. Lakes and reservoirs contain 245 km³ (without Lakes Ladoga and Onego) of water, mean annual river discharge is 57 km³. The present status of the water resources has been formed by the natural, climatic conditions of the region and anthropogenic effects. The chemical composition of the surface waters in Karelia is formed under the conditions of the poorly-soluble parent rocks of the Baltic crystalline shield, well-washed quaternary deposits and high paludification of the territory. The natural quality of the water is modified by sewage discharges, agricultural practices, land reclamation and pollution from atmospheric precipitation during transboundary transports.