Uso de un modelo hidrológico como herramienta de apoyo en la gestión integrada de los recursos hídricos: Casos de estudio: cuenca del río Guadiana, cuenca del río Guadalquivir y cuenca del río Guadalete

Water is an essential resource for socio-economic development and the maintenance of ecosystems, and its sustainable management represents one of the main challenges in the current context of climate change and increasing anthropogenic pressure. In this regard, integrated water resources planning and management require tools that allow understanding and quantifying the processes that determine water availability and quality. The main objective of this thesis is to develop methodologies to identify and quantify the importance of water in watershed management, considering the physical, chemical, and biological processes that determine water quality and quantity, within a context of climate change and land-use change. For this purpose, three Spanish river basins draining into the Atlantic Ocean were selected as case studies: Guadiana, Guadalete, and Guadalquivir. The Soil and Water Assessment Tool (SWAT) hydrological model was applied to simulate streamflow, suspended sediments, and nitrate load at the basin scale. The model was calibrated and validated using time series of hydrological, climatic, and water quality data, along with the necessary input data for its correct implementation in the study watersheds. In addition, climate change scenarios (RCP 4.5 and RCP 8.5) and land-use change scenarios were incorporated to evaluate their impacts on hydrological dynamics and water quality. In the case of Guadalete watershed, the hydrological modeling was complemented with a hydrodynamic model and a pollutant transport model to analyze dispersion in the estuarine system, characterized mainly by marshes under a strong tidal influence. In the Guadiana basin, the model showed excellent performance in simulating streamflow and nitrate loads, with R² values above 0.78 and NSE values above 0.7 during both calibration and validation periods. Land-use and climate change scenarios revealed significant combined effects: the conversion of forest areas into olive groves increased nitrate loads under the extreme scenario RCP 8.5, whereas reductions were observed under the mitigation scenario RCP 4.5. These results highlight the importance of integrating agricultural planning and water resource management to prevent impacts on water quality. In the Guadalete basin, hydrological simulation using SWAT enabled the identification of temporal patterns in streamflow and nutrient transport, highlighting areas with a high degree of anthropogenic influence, where nitrate concentrations depend more on agricultural management than on streamflow. Calibration indicated a systematic bias (high PBIAS values) during wet periods; however, R² values above 0.70 during dry periods demonstrate the model’s ability to reproduce the baseline dynamics of the system. Furthermore, integration with the hydrodynamic model UCA2D and the transport model SCILLA allowed for the analysis of contaminant dispersion in the Cádiz and San Fernando salt marshes. Results showed that low-flow areas retain between 60% and 100% of particles, while tidal propagation (M2 constituent) controls dispersion across much of the bay, with mean errors of only 0.5 cm in amplitude and 0.5° in phase compared to observed data. These findings enabled the development of risk maps and the definition of environmental monitoring strategies, highlighting the importance of scheduling discharges during the ebb phase to optimize contaminant dispersion. In the Lower Guadalquivir, the study assessed the influence of prolonged droughts (2021– 2023) on rice agriculture and water quality. Despite reductions in streamflow between 40% and 60% and in crop yield (up to 97%), nitrate concentrations remained high due to reduced dilution and nutrient accumulation in paddy soils. Improved SWAT calibration enhanced the representation of peak concentrations, achieving an R² of 0.74 and providing a more realistic depiction of nutrient dynamics during drought periods. Finally, this research proposes a methodological framework for the assessment of waterrelated Ecosystem Services (ES), integrating SWAT outputs and georeferenced indicators to identify impacts on aquatic ecosystems and their capacity to provide benefits to society. The combination of hydrological and hydrodynamic modeling, together with particletracking experiments, provides robust and transferable tools for the management of complex river basins, spatial planning, and adaptation to climate and global change scenarios, contributing to sustainable strategies for the preservation of water resources and associated ecosystems.

Author dc:creator

• Buonocore, Cira

Advisors dc:contributor.advisor

• Pérez Cayeiro, María Luisa
• Gómiz Pascual, Juan Jesús

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 Internacional

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

spa

Handle dc:identifier.uri

http://hdl.handle.net/10498/39891

OAI identifier oai:identifier

oai:rodin.uca.es:10498/39891