The landscape-basin approach based on the sequential operation algorithm developed for determining potential and actual water supply of Western Siberia territories is proposed to adjust the existing assessments of water availability. The technique for estimating the water availability at the regional and sub-regional level is presented. The assessment of potential water availability is carried out within the boundaries of landscape provinces, whereas actual water availability is assessed for separate river basins and water management sites. Future water consumption is estimated with due regard for the current peculiarities of water use in Western Siberia regions and trends in water use efficiency, including water capacity of industrial and agricultural production as well as strategic plans for territorial development. Superposition of natural and administrative-territorial boundaries has been achieved through the use of GIS technologies. Assessment results on the potential water availability in 83 landscape provinces of Western Siberia from 12 federal subjects of Russia are presented. Future water consumption has been assessed for the Western Barabinsk landscape province of Omsk oblast where the city of Omsk and the Omskii municipal district are located. The actual water availability has been estimated for a water management site in the Tom river basin, Kemerovo oblast. The size of the Western Siberia population living in conditions of extremely low, very low and low potential water availability has been calculated. The assessment results are given in tabular form and as geoinformation-cartographic models.Keywords: landscape provinces, river basins, water management sites, potential and actual water availability, future water consumption, geoinformation technologies.