The article uses the SWAT model which is a support tool to assess the levels of water resources' assurance on the Ma River basin (Vietnam territory) in 2020. Calculated results of water demand in the basin show that water requirements (mainly for agricultural water supply) is smaller than the volume of income water. However, the distribution of water is not steady over time. the water demand in dry season is large but income water is little, whereas income water in the flood season is plentiful compared to demand water. In the months of the year from May to November, the water in the basin can ensure for the economic social activities. In the months of November to April next year, the total deficit amounted to 596 million m3.