The objective of the study presented here was an analysis of variations in the level of the groundwater table and of the levels of surface water at the melioration object Piwonia-Uhnin. The ditches are 1–1.2 m in depth and overgrown with willow. The water in the ditches stagnates at a very low level, and in some of them it dries out completely. The present differentiation of the level of groundwater table on the studied area was identified on the basis of static hydrometric measurements performed in 9 piezometric wells by means of a hydrogeological whistle and on 7 water-level gauges using a measuring rod. In ditches 2, 3 and 4 the water levels were 15–35 cm, while ditches 1, 5 and 6 remained without water for a long period of time. Unfavourable meteorological factors and the present status of structures regulating water runoff cause an excessive lowering of the groundwater table with the resultant occurrence of water deficit in the soil. Excessive drying of soil is most frequently observed in the case of mineral soils (points 7–9) and, periodically, on strongly transformed shallow peats (points 4–6) situated, in addition, within the zone of effect of the drainage ditch. Depth of drainage exceeds the value of the maximum drainage norm h3. During the early spring period it even happens that the depth of the groundwater table is lower than the value of the drainage norm h1.

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