What have we learnt about Mediterranean catchment hydrology? 30 years observing hydrological processes in the Vallcebre Research Catchments

Abstract

This paper presents the main results obtained from the study of hydrological processes in the Vallcebre Research Catchments since 1988. Distributed hydrometric measurements, environmental tracers and hydrological modelling were used to understand Mediterranean catchment behaviour and to provide new data to help assess the global change effects on these catchments' water resources. Thirty years of hydrological processes observation in the Vallcebre Research Catchments have increased understanding not only of their hydrological response, but also of the main hydrological and erosion processes characteristic of Mediterranean mountain catchments. This paper briefly summarises the main results obtained since 1988 on ecohydrological processes, hydrological response, runoff generation processes, erosion and sediment transport. Some of the main findings from this research are (i) the importance of temporal variability in precipitation to determine the hydrological processes; (ii) the paramount role played by forest cover in reducing soil water content; (iii) the marked influence of antecedent wetness conditions on runoff generation that determine different runoff responses; (v) the dominant contribution of pre-existing water during floods; (vi) the importance of freezing-thawing processes in badland areas on erosion and the role of summer convective storms in controlling sediment transport.

Spatio‐temporal variability of the isotopic input signal in a partly forested catchment: Implications for hydrograph separation

“…Precipitation is seasonal, with autumn and spring usually being wetter seasons, and summer and winter often drier. Summer rainfall is characterized by intense convective events, and winter precipitation is caused by frontal systems, with snowfall accounting for less than 5% of precipitation (Latron, Llorens, et al, ; Latron, Soler, Llorens, Nord, & Gallart, ; Llorens et al, ).…”

Technical note: An improved discharge sensitivity metric for young water fractions

“…The seasonal cycles of stable isotopes in precipitation are damped and phase-shifted as they are transmitted through catchments and thus can be used to infer properties of catchment travel-time distributions (e.g. DeWalle et al, 1997;McGuire and McDonnell, 2006). The young water fraction (F yw ), or the proportion of catchment outflow younger than circa 2-3 months, can be estimated as the ratio between the seasonal cycle amplitudes of stable water isotopes in precipitation and stream water.…”

Particulate Matter Fluxes in a Mediterranean Mountain Forest: Interspecific Differences Between Throughfall and Stemflow in Oak and Pine Stands

“…The precipitation regime is seasonal, with autumn and spring generally being the wet seasons, while summer and winter are drier. Summer rainfall is characterized by intense convective events, while winter precipitation is caused by frontal systems, with snowfall accounting for less than 5% of precipitation Llorens et al, 2018).…”