Assessing agricultural water use in Italy by integrating crop irrigation requirements and spatial data analyses of cultivated areas

Over the past decades, climate change has impacted various facets of life, notably through increasing temperatures, altered precipitation patterns, and the escalation of extreme weather events. These impacts have critical implications for global and local water resources. Considering that the largest portion of water use in the world is for the agricultural sector, it can be concluded that agriculture is deeply interconnected with water and climate. Against the backdrop of climate change, together with the growing human needs that lead to increasing pressure on Earth’s resources, the significance of agriculture in sustaining food security increases, necessitating a comprehensive understanding of water consumption patterns within the agricultural sector. This study sheds light on water usage in agriculture in Italy. It explores official statistics at different administrative levels and gridded data to examine where, how, and for what water is used in agriculture. To achieve this aim, a multifaceted approach integrating various datasets has been adopted. One of the data sources implemented in this study is ISTAT (Italian National Institute of Statistics), which provides data on the agricultural census in 2010. The data are published at different spatial scales from the regional to the commune level. Another data source used is GMIA (Global Map of Irrigation Data), which provides gridded data on the irrigated area and the percentage of the irrigated area by different resources on a global scale. Validating the GMIA data on Italian surfaces shows very small differences in all irrigation areas with respect to the national census data from ISTAT. By using the water usage data from different resources provided by ISTAT and data provided by GMIA, a comprehensive comparison is conducted for the area irrigated by different water resources in each administrative section. ISTAT also provides data on the area irrigated by different irrigation methods and the area irrigated by different crops. A hydrological model developed at the Politecnico di Torino in the past has been employed in this study to estimate crop-specific evapotranspiration rates and irrigation requirements. Through the integration of irrigation requirement data and the area irrigated by different crops, the irrigated water volume required by each crop is estimated for the main crops for which information is available. The national datasets provide the spatial coverage of different irrigation methods in Italy. Due to this, by having the gridded data of irrigation requirements, the amount of water by each irrigation method for a crop is studied. Knowledge of irrigation systems also allowed us to infer, through irrigation efficiency, the water volumes withdrawn from the source. The study results can support policymakers and stakeholders in informed decision-making. They also provide valuable insights for environmental analysis to better understand and address environmental challenges associated with the agricultural use of water.