The water cycle in forest ecosystems has several specifications. Both live and dead plant biomass collects precipitation and regulates the passage of moisture into the soil. Undisturbed forest soils have high infiltration capacity, reduce surface runoff, risk of erosion and retain moisture for vegetation. Forest tree root systems are quite extensive. In the dry season they are less subject to stress because they gain moisture from deeper layers of soil. Risks are long-lasting episodes of drought, when soil water reserves eventually run out. It is important to know the phase of water transition in the soil - plant - atmosphere system throughout the hydrological year. The soil profile has a different character with respect to soil texture and type and specific site conditions. Woody plants vary in moisture requirements and in case of drought stress resistance. Beech is relatively drought-resistant due to its deep roots. At lower altitudes, we see a trend of decreasing rainfall during the growing season and rising temperatures, what may impact the stability of some beech ecosystems. GLOBAL is a simulation model of water movement in soil profile with an emphasis on the root zone. Inputs are information about meteorological elements, vegetation and soil characteristics. The main results are data on soil moisture dynamics in each cm of soil profile during the modeling period. The aim of the work was to model the water regime of forest soil in Bienska dolina during hydrological years 2015 - 2018 and to evaluate the risk of drought based on the results. The first step was soil sampling and laboratory analysis to determine the hydrophysical parameters. Meteorological data as a further input to the model were measured by the Technical University's digital weather stations and data on phenology were estimated based on indices and actual observations. The resulting soil moisture values were compared with the hydrolimit BZD (point of decreased availability). Soil horizons responded differently to changing meteorological situation. In deeper layers, the drought started later, it took longer and its retreat occurred only in the case of longer-lasting rainfall. We have also assessed the precipitation provision indirectly by means of an climate irrigation index that defines the amount of water missing in the ecosystem.