Crop Water Requirements Estimation at Local and Regional Scale

It is recognized that climate change will strongly impact water resources, especially in regions already experiencing a general decreasing trend in water availability, such as Southern Europe. In addition, the competition amongst agricultural, societal and environmental interests for limited water supplies is increasing and this competition can be exacerbated by climate change. Agriculture is a key economic sector in Europe where about 24% of the total water consumption is used for farming, with percentages up to 80% in the Southern regions. In areas characterized by scarce water resources, good water management is crucial to reduce water stress and pursue optimal crop yields at the same time. Therefore, farmers and local governments need to optimize on-farm irrigation to better plan and manage the use of scarce water resources. To support these needs, a geo-spatial tool was developed which estimates crop water requirements for a large array of crops, defining impacts and adaptation potentials to climate change for the irrigation sector. The SIMETAW# soil-water balance model was improved, and included into a spatial platform coupling with climate model outputs, to calculate crop water demand at both local and regional scale. Economically relevant crops at Mediterranean basin scale were considered in this work. Daily data from the COSMO-CLM regional climate model were used to estimate the reference evapotranspiration, the actual evapotranspiration and irrigation requirements, at European scale for both current (1976-2005) and future (2006-2095) climatic conditions. The emission scenarios Representative Concentration Pathway (RCP) 4.5 and RCP 8.5, at 14x14 km spatial resolution, were used for simulations. The SIMETAW# performance at local scale was evaluated in different sites over Europe by comparing the model estimated values and actual evapotranspiration data measured with the Eddy Covariance technique. Furthermore, maps of current and future evapotranspiration values, according to the emission scenarios, were produced at Mediterranean basin scale. Both scenarios showed that reference evapotranspiration will increase more than precipitation in the future, and this will swell irrigation requirements in most areas.