Quaternary sediments in wide flat river floodplains are important accessible and often used resources of drinking water. On the other hand, increasing stress of the human society on water resources and their use cause local deterioration of growth or existence conditions for original forest or meadow ecosystems in affected areas of river floodplains. The paper deals with the evaluation of conditions enabling the coexistence of the Water Supply Podluží withdrawal area situated in the complex of floodplain forests and meadows in Forest District Tvrdonice. Effects of the water drawing are assessed on the establishment of the system of bored wells on the groundwater level based on data of long-term measurements on observation boreholes of the CHMI (Czech Hydrometeorological Institute). Response of a sudden or abrupt change in moisture conditions at the decreased groundwater level on the floodplain forest growth is de-monstrated by the evaluation of a diameter increment of the group of trees of a mature stand, viz narrow-leaved ash (Fraxinus angustifolia V a h l.). On the area of the stand, one of the systems of drawing wells of the Podluží water supply is situated. The ash stand responded to the lowered groundwater level by the significant decrease in diameter increment. With respect to the fact that in the course of next years the level of groundwater table stabilized and a deeper decrease to the sandy gravel layer did not occur the forest stand managed to cope with changed conditions. After revitalization measures, increase in diameter increment to the previous level was noted. A cardinal condition for the optimization of the floodplain forest moisture regime is the capillary saturation of the surface soil layer (with the tree root system) of a depth of about 1.0 to 2.0 m from the groundwater level. Atmospheric precipitation of this climatically dry region can sometimes improve the soil moisture situation, however, in this case it is not decisive for the problem solution.