Non-stationary flood frequency analysis in continental Spanish rivers, using climate and reservoir indices as external covariates

• Published in: Hydrology and Earth System Sciences
• Main Authors: López, J., Francés, F.
• Other Authors: Universitat Politècnica de València. Departamento de Ingeniería Hidráulica y Medio Ambiente - Departament d'Enginyeria Hidràulica i Medi Ambient, Ministerio de Ciencia e Innovación
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union (EGU) 2013
• Subjects: INGENIERIA HIDRAULICA; Arctic; Rigby; North Atlantic; North Atlantic oscillation
• Online Access: http://hdl.handle.net/10251/45322; https://doi.org/10.5194/hess-17-3189-2013

Recent evidences of the impact of persistent modes of regional climate variability, coupled with the intensification of human activities, have led hydrologists to study flood regime without applying the hypothesis of stationarity. In this study, a framework for flood frequency analysis is developed on the basis of a tool that enables us to address the modelling of non-stationary time series, namely, the "generalized additive models for location, scale and shape" (GAMLSS). Two approaches to non-stationary modelling in GAMLSS were applied to the annual maximum flood records of 20 continental Spanish rivers. The results of the first approach, in which the parameters of the selected distributions were modelled as a function of time only, show the presence of clear non-stationarities in the flood regime. In a second approach, the parameters of the flood distributions are modelled as functions of climate indices (Arctic Oscillation, North Atlantic Oscillation, Mediterranean Oscillation and the Western Mediterranean Oscillation) and a reservoir index that is proposed in this paper. The results when incorporating external covariates in the study highlight the important role of interannual variability in low-frequency climate forcings when modelling the flood regime in continental Spanish rivers. Also, with this approach it is possible to properly introduce the impact on the flood regime of intensified reservoir regulation strategies. The inclusion of external covariates permits the use of these models as predictive tools. Finally, the application of non-stationary analysis shows that the differences between the non-stationary quantiles and their stationary equivalents may be important over long periods of time. This work has been supported by CONACYT of Mexico and the Spanish research projects FLOODMED (CGL2008-06474-C02-02/BTE) and SCARCE-CONSOLIDER (CSD2009-00065). We acknowledge D. M. Stasinopoulos, R. A. Rigby and P. Akanziliotou for making the GAMLSS package freely available in R. We would also like to thank J. ...