Modeling impacts of climate change on blue and green water, and crop yield using SWAT + in Lake Tana sub-basin (Ethiopia).

Understanding the impacts of climate change on blue and green water, as well as crop yield, is crucial for developing climate-resilient systems to mitigate water and food insecurity. This study aims to assess the impacts of climate change on blue and green water, and crop yield under different climate change scenarios in the Lake Tana sub-basin, Ethiopia. The research integrates observational climate datasets, Global Climate Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6), and the enhanced Soil and Water Assessment Tool (SWAT+) to achieve this objective. The SWAT + model was calibrated and validated using monthly streamflow data and the long-term mean annual maize yield data. We analyzed the projected impacts of climate change on blue and green water and crop yield for the 2050s (2041–2070) and 2080s (2071–2100) periods under SSP2-4.5 and SSP5-8.5 scenarios, using the baseline climate data (1992–2021) as a reference. Results indicate effective model simulation of streamflow and crop yield. Rainfall and temperature are expected to rise in both future periods and scenarios. At areal average scale, blue water is projected to increase by 11.1%–13.4% under SSP5-8.5, with no change under SSP2-4.5 in the 2050s and 2080s. Green water flow (GWF) is expected to rise in 2050s (8.5–12.3%) and 2080s (10.9–18.2%) in both climate change scenarios. Green water storage (GWS) is projected to increase by 5–20.7% under the SSP5-8.5 climate change scenario in the 2050s and 2080s, but to decline by 1.7–7.4% under the SSP2-4.5 scenario during the same periods. However, crop yield is anticipated to decline by 30.1%-41.5% in the 2050s and 26.6%-41.1% in the 2080s. The projected increase in blue water under the SSP5-8.5 climate scenario has positive implications, as it can be conserved and utilized for agricultural production during seasonal water shortages. Conversely, the increase in GWF highlights the need for effective water management strategies to minimize losses under changing climatic conditions. The anticipated reduction in GWS under the SSP2-4.5 scenario indicates a decline in soil water availability for crop growth, which will negatively affect agricultural production. Similarly, the projected decrease in maize yield poses serious implications for food security in the region. Overall, these findings emphasize the urgent need for agro-hydrological interventions to mitigate climate change-induced water and food insecurity in the study area and other regions with comparable environmental and climatic settings.