Assessing climate-driven changes in crop water demand using CMIP6 data: implications for water management and decision making

Climate change is affecting water availability and irrigation management in agricultural systems, particularly where climatic pressures interact with technical and regulatory constraints. This study presents a case study developed through collaboration between academic research and local water management authorities, specifically the Piave land reclamation consortium (Consorzio di Bonifica Piave, northeastern Italy). This study investigates how projected climatic changes may impact hydrological conditions and crop water availability within a complex socio-ecological system. We used climate projections (CMIP6; CMCC-ESM2 model; SSP5-8.5 scenario) to assess changes in temperature, precipitation, potential evapotranspiration, and aridity indicators. These variables were combined with crop-specific coefficients to estimate irrigation water requirements for the main crops cultivated (maize, soybean, wheat, alfalfa, and vineyard) under near-term (2021–2040) and future (2041–2060) climate scenarios. The analysis focuses on relative changes in irrigation demand and their implications for water management. Results indicate a systematic increase in irrigation demand per unit area across all analysed crops. Projected changes show relative increases in specific irrigation requirements of 10–15% for arable crops and over 20% for forage crops, while key crops for the area such as grapevine, historically characterised by very low irrigation requirements (or no irrigation), exhibit the highest relative increases. These trends are mainly driven by increased evaporation rather than changes in total precipitation, leading to a growing imbalance between water demand and effective water availability during the irrigation season. Climatic pressures are also aggravated by technical and regulatory constraints, such as environmental flow requirements defined under historical hydrological conditions, which reduce operational flexibility during drought periods. Despite uncertainties inherent in climate and hydrological modelling, the proposed approach provides a bottom-up framework for informed decision making. The methodology is also transferable to specific sub-areas of the consortium, supporting targeted planning and project design aimed at enhancing irrigation resilience under future climate conditions.