Water in the vadose zone is an essential part of the global water cycle making up some of the largest freshwater resources on Earth. Climate as well as land use change are known to alter water fluxes in the vadose zone, and thus changes in groundwater recharge rates. Despite the fact that any change of groundwater recharge would have dramatic impacts on the availability of water, and hence, severe economic and ecological consequences, we know little about past and future groundwater recharge rates for Austria. Therefore, the objective of this study was to quantify and predict groundwater recharge rates, their variability and uncertainties and the potential impacts for land use and water management in Austria. Soil water fluxes at 14 Austrian monitoring sites were influenced by the East-West gradient in altitude and climatic conditions at the local and regional scale. At the dry and warm eastern locations, recharge rates were low and seasonality was high since near zero recharge was estimated for the summer months. At the western and central Austrian locations, the fraction of recharge from precipitation and absolute recharge estimates were high and temporal variation in recharge and actual evapotranspiration was influenced by snow accumulation and snow melt. For predicting future recharge rates at the local scale, uncertainties were mainly related to the differences in climate projections. Model results for groundwater recharge rates according to the selected climate projections indicated increasing groundwater recharge rates at locations in the East of Austria, whereas predictions were ambivalent at locations in central and western Austria. For these sites, one scenario predicted a decrease in annual recharge rates of up to 20% in the far future (2071-2100) as compared to the past (1991-2020). For the nationwide analysis, spatial information on soil hydraulic properties were derived by combining soil data from different sources. Two methods based on machine learning approaches were tested to directly and indirectly estimate saturated hydraulic conductivity (Ks). While the resulting soil property maps of the indirect approach were able to largely reproduce the original data variability, the prediction of Ks includes high levels of uncertainties and the predicted vertical distribution of Ks is not plausible. The spatial distribution of Ks in the direct approach resembles available global maps. In the existing global Ks maps as well as in the results of the direct approach the small-scale variability of Ks is reduced. The integrated modelling framework for the Seewinkel region showed that vineyards are the dominant land use, regardless of the climate scenario if there are no restrictions on groundwater extraction for irrigation. Irrigation water use and regional net benefits of agricultural production continuously decrease with more restrictive policies on groundwater extraction for irrigation, with largest decreases under a dry and smallest decreases under a wet climate scenario, whereby cropland and other (abandoned) land gain in importance. If groundwater extraction for irrigation is restricted, high flexibility in land use is required to efficiently adapt land use and management to the climate scenarios. Further a Bayesian Network was developed for the Seewinkel region that can be used for reasoning and analysis of the design of groundwater policies and for giving information on the influence of irrigation water availability on agricultural productivity and farmers’ income. This integrated modelling framework was also applied to Upper Austria for testing efficient agricultural adaptation to three precipitation scenarios with declining precipitation sums and more frequent dry spells as well as to groundwater use scenarios, limiting irrigated agricultural land.

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