Within the limits of Byelorussia neotectonic processes controlled the pattern of the drainage net belonging both to the Black and Baltic sea drainage basins to a considerable degree. Differentiated neotectonic movements up to 150 to 170 meter range resulted in a regional monocline sloping towards the Baltic Sea, the main water divide thus having come into being. The present day river valleys inherited the Neogene valleys only in small fragments and have different direction over considerable areas. Some of lake depressions and local features of river valleys are due to local structures evolution. The hydrographic net often reflects structure of the glacial complexes.