Author(s): Veronica Ruiz-Ortiz; Jorge M. G. P. Isidoro; Helena Maria Fernandez; Fernando M. Granja-Martins; Santiago Garcia-Lopez

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Keywords: Rainfall; Physiography; Multilinear regression; Map algebra; Iberian Peninsul

Abstract: Rainfall plays a fundamental role in most of the Earth natural physical processes, such as river morphodynamics, erosion, or sediment transport. On the other hand, water resources are intrinsically dependent of human activities like water supply or irrigation. As so, an accurate quantification of rainfall is fundamental for water resources planning and management, the design of hydraulic structures, and to evaluate extreme events (droughts and floods), among others. This work presents a computational and experimental methodology using multilinear regression and algebra map supported by a geographic information system, for detailed rainfall mapping. The proposed methodology is supported by five phases: i) characterisation of the study area; ii) compilation, analysis and treatment of rainfall data; iii) definition and evaluation of physiographic variables correlated with rainfall; iv) multilinear regression to explore the relationship between rainfall and physiographic variables and, finally, v) generation and analysis of rainfall models using map algebra tools. This methodology was applied to the Southwest of the Iberian Peninsula (28,860 km2), in an area comprising four Portuguese regions and one Spanish province. Monthly rainfall records from a network of 235 raingauges was analysed, from which the datasets were completed from 163 weather stations for the last four decades (1980-2020). For the multilinear regression, five physiographic variables were selected from an initial set of 10. These five selected variables (elevation, distance to coast, geographic coordinates (X, Y) and Normalized Difference Vegetation Index (NDVI)) were the ones with a stronger statistical correlation with the rainfall records. Finally, rainfall models for the wet and dry semesters were generated with the algebra map tools. Results from this study show that the proposed methodology based in physiographic models can be useful to estimate rainfall variability across space in regions with a lower density of raingauges, or to improve rainfall estimation between raingauges.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221386

Year: 2022