Crop growth and yield are affected by water use during the season: the green water footprint (WF) accounts for rain water, the blue WF for irrigation and the grey WF for diluting agri-chemicals. We calibrated crop yield for FAO’s water balance model “Aquacrop” at field level. We collected weather, soil and crop inputs for 45 locations for the period 1992–2012. Calibrated model runs were conducted for wheat, barley, grain maize, oilseed rape, potato and sugar beet. The WF of cereals could be up to 20 times larger than the WF of tuber and root crops; the largest share was attributed to the green WF. The green and blue WF compared favourably with global benchmark values (R² = 0.64–0.80; d = 0.91–0.95). The variability in the WF of arable crops across different regions in Europe is mainly due to variability in crop yield ( $\overline{cv}$ = 45%) and to a lesser extent to variability in crop water use ( $\overline{cv}$ = 21%). The WF variability between countries ( $\overline{cv}$ = 14%) is lower than the variability between seasons ( $\overline{cv}$ = 22%) and between crops ( $\overline{cv}$ = 46%). Though modelled yields increased up to 50% under sprinkler irrigation, the water footprint still increased between 1% and 25%. Confronted with drainage and runoff, the grey WF tended to overestimate the contribution of nitrogen to the surface and groundwater. The results showed that the water footprint provides a measurable indicator that may support European water governance.

Crop productivity and water consumption form the basis to calculate the water footprint (WF) of a specific crop. Under current climate conditions, calculated evapotranspiration is related to observed crop yields to calculate WF. The assessment of WF under future climate conditions requires the simulation of crop yields adding further uncertainty. To assess the uncertainty of model based assessments of WF, an ensemble of crop models was applied to data from five field experiments across Europe. Only limited data were provided for a rough calibration, which corresponds to a typical situation for regional assessments, where data availability is limited. Up to eight models were applied for wheat. The coefficient of variation for the simulated actual evapotranspiration between models was in the range of 13%–19%, which was higher than the inter-annual variability. Simulated yields showed a higher variability between models in the range of 17%–39%. Models responded differently to elevated CO₂ in a FACE (Free-Air Carbon Dioxide Enrichment) experiment, especially regarding the reduction of water consumption. The variability of calculated WF between models was in the range of 15%–49%. Yield predictions contributed more to this variance than the estimation of water consumption. Transpiration accounts on average for 51%–68% of the total actual evapotranspiration.

Assessment of agronomic drought occurrence and severity in agricultural regions of Slovakia is presented in the paper. Drought severity assessment is based on the soil water dynamics simulation by agroecological model Daisy. Daily meteorological data from the years 1961-2012 from 31 localities were used in simulations. Criteria for the drought occurrence were 1) available soil water content below 50% of available water capacity, 2) soil water content below long-term average soil water content and 3) duration of continuous drought for fifteen or more days. Standardized index of daily available soil water content was used for drought severity classification. According to the index the drought is categorized into four degrees of severity from mild to extreme drought. Cumulative sum of available soil water index was used to drought quantification throughout its duration. Normal climate period 1961- 1990 was chosen as reference period to enable historical comparison of drought severity as well as climate change impacts. Extreme drought of the largest spatial extent was identified in 1990. Extreme drought occurred regionally in the southwest Slovakia in 1978 and in the southeast Slovakia in 1986, respectively.

Climate change impacts on soil organic carbon sequestration rate were simulated by agroecological model DAISY. Daily meteorological data for the Danubian Lowland up to 2100 were generated according to emission scenarios SRES A2 and B1 using general circulation model CGCM3.1. Effect of gradual increase of CO₂concentration in the atmosphere was taken into account. Various crop rotations as well as various management practices including irrigation and crop residuals incorporation were considered in three variants: i/ rainfed, residuals not incorporated, ii/ irrigated, residuals not incorporated, iii/ summer crops irrigated and residuals incorporated. Modelling outputs confirm that conventional rainfed agro-technical practices without incorporation of crop residues resulted to significant loss of soil organic carbon in soil profile towards more distanced time slices. The irrigation and the incorporation of crop residuals including stems and leaves can reduce soil organic carbon losses. If it is combined with proper crop rotation the soil organic carbon stock in soil profile can even increase.