Cross-Comparing Modelling Approaches for Hydrological Ecosystem Services in a Semi-Arid and Highly Anthropogenic Area

Hydrological Ecosystem Services (HES) such as water supply and purification are fundamental for sustaining human well-being and guiding sustainable land and water management, especially in regions facing water scarcity and intense anthropogenic pressure. Here we applied and compared the new version of the Soil and Water Assessment Tool (SWAT+) and the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) in the Campo de Cartagena (southeastern Spain), an intensively cultivated catchment. Both models, as well as a coupled version (SWAT+InVEST), were evaluated for their ability to simulate water yield and nutrient export, assessing performance, suitability, and complementarity under conditions of high human pressure, water scarcity, and ecological fragility. Unlike previous comparative studies focused on topographically diverse or forested basins, our work offers new insights into model behaviour in semi-arid and heavily modified landscapes. InVEST tended to overestimate water yield and underestimate nutrient export, while SWAT+ produced more realistic estimates for both HES. By coupling both models, we derived intermediate values that helped reduce the uncertainty of the InVEST model. Our findings offer guidance on model selection based on environmental complexity, data availability, and the trade-off between accuracy and usability. SWAT+ shows greater reliability in complex environments, while InVEST remains useful for broad-scale or rapid assessments in less demanding catchments. This study improves the reliability of HES assessments in catchments under intense anthropogenic pressure and supports more targeted ecosystem service management in semi-arid regions.