Modeling crop water demand to support adaptation strategies in Mediterranean environment under climate change

Water scarcity is arguably a pressing issue for the 21^st century in Mediterranean areas, due to limited water resources, expansion of irrigated area to sustain food security and climate change. Water extraction for agriculture sector account about to 70% of global water use, and this demand peaks to 80% of total water withdrawal in several southern Mediterranean countries. In this study, the impact of climate change on evapotranspiration demand, crop water requirements, and crop yield losses due to water shortage, were assessed by using the Simulation of Evapotranspiration of Applied Water (SIMETAW_GIS) model. This crop-soil-water model was implemented over the Sardinia island, a region with a typical Mediterranean climate and agriculture characteristics, assuming impact of climate change for a whole range of relevant Mediterranean crops (Wheat, Barley, Sugar beet, Potato, Lentil, Almond, Maize, Wine Grape, Table Grape, Tomato, Rice, Artichoke, Alfalfa, Olives, Improved Pasture and Orange). Under present analysis, daily climate data from five Earth System Models dynamically downscaled to a spatial resolution of 0.11-degrees (~11 km) from the  EURO-CORDEX project domain and available from the Copernicus Climate Data service (https://climate.copernicus.eu/) were retrieved and ensembled. The impact of climate change on crop water requirements was evaluated under historical (1976-2005) and future (2036-2065) climate conditions following different Representative Concentration Pathways (RCPs: 2.6, 4.5 and 8.5), representing alternative mitigation policies and future emission scenarios.

In the Sardinia region, results show a variegated increase of crop water demand between future (2036-2065) and historical conditions (1976-2005) for different crops, which may pose a challenge for water resource management, especially considering water use conflicts among different sectors. On average wheat and barley will foresee the most significant increase of crop water requirements, ranging on average by 12 to 14% under different RCPs. Other crops (e.g. almond, maize, wine grape, and pasture) are projected to foresee still significant increases of crop water demand, varying between 4-8%.  This work provides information that can support farmers and decision managers to evaluate climate change adaptation strategies linked to different cropping patterns to increase use efficiency of water resources for a more sustainable agriculture production under climate change.