ABSTRACTComprehensive, steady‐state investigations were carried out on plots adjoining drained tracts in Byelorussia's southern marshified lowlands, plots encompassing different plant cover, types of soil and ground‐water levels, to ascertain the influence of ground‐water level and its fluctuations on the formulation and productiveness of forest, field and meadow verdure.It was established that when the ground‐water level diverged—higher or lower—from optimum (i.e., depth approximately equal to the height of the capillary lift), productiveness of plants fell; that intensive utilization and drying of peat bog soils led, as a rule, to mineralization of the peat and air and water erosion (the lower the level falls the more intensively mineralization proceeds). It is calculated that with cultivated crops the loss of peat is some 10 tons per hectare per year, 5‐6 with cereals and 2‐3 with grasses.Lowering the ground‐water level on any area leads to changed levels on adjacent areas, the ground waters being elements of a unified system. In the sandy soils most widespread in the Byelorussian lowlands, lowering of ground‐water level perceptible in the vital activities of plants occurs up to 2 kilometers from the drained tract. In all cases reductions in ground‐water level and in the duration and height of flooding led to degradation of the meadows.It is concluded that comprehensive calculations on the possible harmful effects of drainage reclamation‐caused changes in a large territory's hydrological regime are a prerequisite for rational utilization of the land and maximum productiveness and preservation of the natural landscape.