The study allocates 12 basic water-modular areas of the Altay Mountains, five of which belong to the Ob basin, the others - to the systems of an internal drain of the Mongolian hollows. It is shown, that river system of Chuya - the large top Katun inflow - penetrates three enclosed inside one after another mountain tectonic hollows. The researcher draws a conclusion on necessity to allocate this problem as an independent scientific direction in neo-geomorphology.

Key words: Altai mountains, division into districts of a river network, catchment basins, intermountain tectonic hollows, endogenous and exogenous factors of relief formation.