Taking into account the limited water resourced in Poland, water management should aim at improvement of utilisation of natural resources of water at the place of their formation. An example of such activity is the method of year-round regulation of drainage from the melioration system applied at the object Samotwór. Estimation of the effectiveness of the solution applied was based on analysis of distribution of water reserves for the months of the vegetation season in characteristic soil profiles with depth of 1.0 m. Within the scope of field and laboratory experiments the current resources were determined, as well as the potential water retention capacity of the soil up to the value of field water capacity (FWC) and the maximum permissible moisture (MPM – adopted value 85% FuWC). The study showed that in the period of 1995–2012 the potential retention reserve (SRR) of the soil profiles under analysis, calculated to the FWC, varied on average from 21 mm in April to 84 mm in August, and calculated to the MPM – from 115 mm in April to 177 mm in July. The long-term study revealed the existence of relatively large, and safe for the crops, possibilities of seasonal retention of water in the soil profiles.