The paper presents preliminary results of research conducted in 2015 in the Przebędowo catchment (in the area directly adjacent to the reservoir), located in the Wielkopolska province, 25 km north of Poznan in the Murowana Goślina municipality. Analyzed reservoir was created in the valley of the Trojanka river, from km 6 + 915 to km 8 + 371 of its course by the Greater Board of Land Reclamation and Water Facilities in Poznan and was put into operation in November 2014. Clay dam leading to the reservoir is a Class IV, its length is 334 m, with a height of 3.30 m. The tank with a length of 1450 m and a maximum width of 120 m, with a normal level of impoundment (NPP) above sea level, has an area of 72,50 m lagoon 12,03 ha and capacity 0.162 million m³. Based on the research, it was found that despite the weather conditions , significant impact on the water levels in the reservoir and also in the area immediately adjacent had impoundment of water. The study found also a strong relationship between retention water in the reservoir and groundwater in the area adjacent on the side of analyzed wells. Conducted for year 2015 relationships calculations between these values showed a strong relationship between them. The calculated correlation coefficients (r) ranged from 0.87 for wells P-16 to 0.92 for P-wells 18 and according to these for all analyzed wells were significant at α = 0.01.