A Comprehensive Environmental Cost–Benefit Analysis of Using Reclaimed Water for Irrigation in Southern Spain

Water scarcity and pollution are critical challenges affecting agriculture and aquatic ecosystems. This study evaluates the environmental benefits of using reclaimed water (RW) for irrigation in southern Spain by applying a comprehensive cost–benefit analysis (CBA) to a water reuse project. This method allows us to assess financial feasibility and environmental externalities of RW use for irrigation, with particular focus on the reduction in eutrophication and greenhouse gas emissions. Furthermore, the proposed CBA highlights the potential of RW to provide essential nutrients for crops, reduce reliance on synthetic fertilizers, and mitigate the ecological impact of fertilizer manufacturing and transportation. Results indicate that, while the direct financial returns of RW are limited, the integration of environmental benefits significantly improves the overall economic viability of water reuse projects. Furthermore, sensitivity analyses suggest that policy measures, such as adjusted water pricing and financial incentives, could enhance the adoption of RW in agriculture. This study supports the role of RW as a sustainable alternative for irrigation, contributing to water conservation, pollution reduction, and climate resilience. Future research should focus on long-term agronomic impacts, optimized pricing models, and policy frameworks that promote water reuse as a key strategy in sustainable water management.