Impact of climate change on the irrigation water demand of rainfed crops in the Southern and Steppe regions of Rio Grande do Sul, Brazil.

Proper management of natural resources is essential to improve agricultural productivity and reduce potential losses. The PROJETA platform provides global climate models regionalized by the ETA model, enabling more accurate climate projections for specific regions. This study aimed to evaluate the influence of climate change on irrigation water demand using three global climate models (CANESM2, HADGEM2-ES, and MIROC5) regionalized by the ETA model for the baseline period (1961-2005) and two future scenarios (RCP 4.5 and RCP 8.5). The scenarios were subdivided into three future periods and analyzed for 27 municipalities located in the Southern and Steppe regions of Rio Grande do Sul using the SWAP (Soil, Water, Atmosphere and Plant) model. The results indicate variations in irrigation water demand among models and scenarios. Some projections suggest an increase in irrigation requirements in certain municipalities, while others indicate a reduction when compared to the baseline period. The projected increase in water demand is mainly associated with rising temperatures, which may intensify crop transpiration and soil water evaporation. These findings highlight the importance of climate adaptation strategies and improved water resource management to support sustainable agricultural production under future climate conditions.