Long-term time-scale bonds between discharge regime and catchment specific landscape traits in the Spanish Pyrenees

Abstract

An analysis of long-term databases with information on precipitation and discharge records was undertaken to characterize the temporal structure response of four experimental catchments, located in the Central Spanish Pyrenees, with a gradient of land-cover (from a relatively pristine forested catchment, through an abandoned cultivated catchment with progressive plant recolonization, to an afforested catchment and ending with a degraded badlands catchment). Precipitation and discharge records are non-stationary and the wavelet transform methodology was thus applied to perform a temporal scale-by-scale analysis of each catchment response to the hydroclimatic characteristics of the area. This temporal decomposition analysis illustrates how land-use and land-cover legacy control the temporal distribution of flow events occurring at different and non-similar time-scales, thus reflecting the timing, variability and physical mechanisms of water storage/transport in each catchment. Intra-annual and annual time-scales are led by climatological characteristics of the catchment sites (seasonal patterns of mountainous Pyrenees catchments). Multi-year scale is mainly shaped by land-cover and land-use legacy. Badlands catchment, with its large proportion of bare land, shows a discharge response closely synchronized with precipitation patterns for all time-scales. On the contrary, for the forested catchment the global hydrological response is mainly governed by the multi-year time-scale. Afforested catchment and abandoned cultivated catchment, which move towards a pristine forest response, are impacted by the former grazing and agriculture activities and intra-annual temporal variability still play a major role on the global discharge response of the catchment. This suggests that vegetated catchments located in the same region can show hydrological responses at different time-scales to the same climatic input. We argue that differences in land-cover and historical land-use changes are not only valuable to understand the current discharge temporal behaviour, but they will also play a significant role in characterizing the future catchment dynamics due to changing climate conditions.

Keywords: Environmental technology; Land-cover; Land-use; Long-term databases; Pyrenees journal: environmental research; Wavelet transform methodology.