Water Resources Management in Coastal Areas Under Climate Change and Irrigation and Fertilization Scenarios

Abstract The study aims to analyze the effects of climate change, irrigation and nitrogen fertilization practices and water reserve strategies, on water resources, aimed at nitrogen use efficiency, groundwater nitrate pollution, groundwater budget, and seawater intrusion. Intensive groundwater abstraction for irrigation and nitrogen fertilization has led to a substantial water deficit, rising nitrate pollution, and seawater intrusion in the Almyros aquifer system. The analysis employs an Integrated Modelling System (IMS) to simulate coastal water resources, incorporating models for surface hydrology (UTHBAL), reservoir operations (UTHRL), groundwater hydrology (MODFLOW), nitrate leaching/crop growth (REPIC), nitrate pollution (MT3DMS), and seawater intrusion (SEAWAT) to capture the complex interactions between climate, hydrology, and agricultural practices. Climate projections for Representative Concentration Pathway 8.5 (RCP 8.5) from the Med-CORDEX (Mediterranean Coordinated Regional Downscaling Experiment) database for precipitation and temperature are bias-corrected with Empirical Quantile Mapping and used to estimate the effects of climate change. Irrigation scenarios, including base irrigation and deficit irrigation, as well as reduced nitrogen fertilization, are evaluated to determine their effects on water resources management and sustainability. The study’s results highlight a significant decline in water availability across climate models, with reduced runoff and groundwater recharge projected for the Almyros Basin. Increasing nitrate concentrations and chloride levels suggest worsening water quality, posing risks of seawater intrusion and nutrient pollution. The Nitrogen Use Efficiency index (NUE) improves under reduced nitrogen fertilization, supporting more efficient nutrient use and reducing excess nitrogen losses. The findings highlight critical water quality and quantity challenges, aligning mainly with Sustainable Development Goal 6, and following SDGs 9, 12, and 13 by promoting efficient resource use, pollution reduction, and climate resilience, guiding adaptation strategies for mitigating water scarcity under climate change.