Climate Change impacts on streamflow dynamics and irrigation water availability in the Vea Catchment, Ghana

Abstract

Climate change poses a major threat to water security and agricultural sustainability, particularly in semi-arid regions where livelihoods depend heavily on climate-sensitive water resources. This study assesses the impacts of climate change on streamflow dynamics and irrigation water availability in the Vea Catchment, Ghana, using an integrated modeling framework that combines climate projections, hydrological simulations with the Soil and Water Assessment Tool (SWAT), and water allocation analysis using the Water Evaluation and Planning (WEAP) model. Climate projections for the near future (2023–2052) and far future (2071–2100) were derived from the ensemble mean of six global climate models under SSP2–4.5 and SSP5–8.5 scenarios, using bias-corrected daily temperature and precipitation data. Results indicate significant declines in streamflow, particularly during the dry season, highlighting the catchment’s high hydrological sensitivity to climate variability. Ensemble mean streamflow is projected to decrease by 28–37% under SSP2–4.5 and 36–42% under SSP5–8.5. Consequently, irrigation water availability is expected to decline, with average unmet irrigation demand reaching approximately 30 Mm³ by the late-century period (2071–2100) under the SSP5–8.5 scenario. Total unmet water demand is projected to increase by up to 14.7%, intensifying competition among water-use sectors and threatening dry-season irrigation and agricultural productivity. These findings underscore the urgent need for adaptive and integrated water management strategies to enhance system resilience and ensure sustainable water use under changing climatic conditions.