There is abundant scientific evidence that Alpine forests (will) suffer from impacts of climate change. Rising temperatures and drier conditions (will) force current forests and their composition of tree species towards their ecological limits. Developing strategies towards climate-resilient forest management requires reliable estimates of future growth conditions, including plant-available water . Current and future changes of water balance components in forests can be efficiently simulated using soil-vegetation-atmosphere transfer (SVAT) models, reproducing the interactions and fluxes between soil, plants and atmosphere based on physical laws and empirical relationships. In the present study a lumped SVAT model (LWF-Brook90) was employed for assessing the water balance at 2.009 mapped forest sites in Tyrol and Vorarlberg (Austria). The soils were parameterized based on detailed records of soil surveys and results of laboratory tests. For the vegetation, established generic parameterizations of native tree species were used. Serving as an indicator for the site-specific moisture regime, the mean annual sum of the transpiration deficit (Tdef) was computed for current (1991-2020) and future conditions (2036-2065, 2071-2100), considering three selected climate change scenarios. The results were then upscaled using digital mapping techniques to derive maps of Tdef for the different periods and climate change scenarios, ensuring spatial consistency across model runs. Tdef generally shows a distinct, non-linear increase. Depending on the considered climate change scenario, this increase may reduce the resistance of current tree species composition against biotic disturbances or even might exceed their ecological limits, particularly towards the end of the century. The results also show regional patterns of Tdef, mainly due to spatial climate variability, topographic conditions in a mountain environment, and differences in climate model projections. In combination with further site factors controlling tree growth, the project results will have implications on the management of climate-resilient forests.