Exploitation of newly constructed Malczyce barrage will split the adjacent valley into two zones – above the barrage water will infiltrate from the river into the valley, however, below the dam, Odra will still draining river. Delivery of water from the upper level of the dam will help to improve water conditions of lands located below the damming. On the right bank, at the height of the step, built surge tank, from which water will be collected include forests for irrigation and to supply the upper section of the watercourse Młynna-Brzeźnica and areas used for agricultural purposes in the immediate vicinity of the watercourse. After the construction of Malczyce barrage Odra, in the zone located above the dam, will stay a drainage river. The water conditions of this area can be improved by supplying water from the compensation reservoir located on upper position of the dam. An influence of increasing of water level in Młynna-Brzeźnica river on groundwater level in adjacent areas was analyzed in the paper. Groundwater levels and their increasing with comparison to levels observed in September 2013 was calculated using a mathematical model. An effective range of influence of Młynna-Brzeźnica river for flow intensity 0,1 and 0,5 m3∙s‑1 was discussed.