Damming the Oder river in Brzeg Dolny caused the change of character of the river in relation to the adjacent areas. Lowering of water levels in the river and as a result of groundwater is a consequence of increased linear and local erosion process, which is still below the barrage. In this area the river drained the adjacent areas. This paper presents the evaluation of the development and trends of groundwater depths in the Oder valley below the dam in Brzeg Dolny. For the purposes of this study the area of the Oder valley was divided into two zones, depending on the dominance of the factors influencing on the level of the groundwater. The paper presents the minimum, maximum and average values of groundwater depths for selected measurement points in the following years with the division into two zones. The analysis were done on the background of climatic, hydrographic and hydrogeological conditions and water levels in the Oder river in the Brzeg Dolny and Malczyce sections. The conducted analysis showed significant changes of the ground water depths in the Oder valley over the 42 years. It was shown a connection between the depth of the groundwater and distance from the Oder river bed.