Identifying trends in the water cycle of the “Gave de Pau” and “Gave d'Oloron” catchment areas in the northern Pyrenees
Résumé
Studies carried out in France show that the southwestern part of the country will be one of the regions most affected by climate change impacts. This study aimed to identify trends in the different components of the water cycle in this region. The study was performed using statistical methods commonly used to analyse hydrological time series, such as the Mann-Kendall and Pettitt non-parametric tests. The tests were applied to several variables, including rainfall, effective rainfall, mean annual discharge, low-flow discharge and piezometric level. Over the long term (1959-2014) and based on Météo France data, the study identified significant negative trends in evapotranspiration in both catchment areas, and in effective rainfall in the Gave d'Oloron basin. Regarding river discharge, significant negative trends were identified for the 1965-2011 period in the mean annual discharge of the 8 rivers studied and in low-water discharge for 6 of the rivers. The Sen slopes calculated show drastic reductions in mean discharge over the same period (up to 50%). However, the same test applied over a longer period was not always significant (1912-2016, Gave d'Oloron), which underlines the importance of the period chosen for analysis. Regarding piezometric levels, significant positive trends were identified in the mean annual water level during the period for which data was available (2001-2015). It is important to note that significant positive trends were also identified in the mean annual discharge of rivers over the same period.
Domaines
Hydrologie
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