Abstract
<title>Abstract</title> <p>Increased global warming is projected to alter rainfall patterns, intensifying pressure on water availability. The already acknowledged 2.3 – 2.5◦C temperature increase under current policies calls for progress in adaptation planning. We developed a Climate, Land, Energy, and Water systems (CLEWs) model with explicit seasonal crop-growing stages and seasonal hydrological cycles. We applied the method to the case study of Ethiopia and used it to explore the impact of seasonal water variability on agricultural planning in an integrated model and investigate the impact of the adaptation of the agricultural sector on water stress. We compared standardised IPCC scenarios with historical trends and observed that seasonal differences in precipitation increase by 9.5% and 20% on a national scale for medium (RCP4.5) and high (RCP8.5) impact climate trajectories. We found that integrated resource models that do not account for seasonal hydrological variability overestimate available renewable water. Our results show an increase of 223% and 272% of groundwater recharge and surface water in scenarios without seasonal hydrological cycles. This impacts the use of resources in water scarce scenarios (RCP8.5) where the presence of seasonal variability leads to a 63% increase in irrigated area. This study enhances the representation of the water sub-system in an integrated resource model and lays the foundation for progress in adaptation planning.</p>