The hydrological response of a small agroforestry catchment in northwest Spain (Corbeira catchment, 16 km 2 ) is analysed, with particular focus on rainfall events. Fifty-four rainfall-runoff events, from December 2004 to September 2007, were used to analyse the principal hydrological patterns and show which factors best explain the hydrological response. The nonlinearity between rainfall and runoff showed that the variability in the hydrological response of the catchment was linked to the seasonal dynamics of the rainfall and, to a lesser extent, to evapotranspiration. The runoff coefficient, estimated as the ratio between direct runoff and rainfall volume, on an event basis, was analysed as a function of rainfall characteristics (amount and intensity) and the initial catchment state conditions prior to an event, such as pre-event baseflow and antecedent rainfall index. The results revealed that the hydrological response depends both on the soil humidity conditions at the start of the event and on rainfall amount, whereas rainfall intensity presented only a significant correlation with discharge increment. The antecedent conditions seem to be a key point in runoff production, and they explain much of the response. The hydrographs are characterized by a steep rising limb, a relatively narrow peak discharge and slow recession limb. These data and the observations suggest that the subsurface flow is the dominant runoff process.Key words rainfall-runoff events; temporal variability; runoff coefficient; subsurface flow; agroforestry catchment; northwest Spain Réponse pluie-débit et coefficients de ruissellement événementiels dans une région humide (nordouest de l'Espagne) Résumé La réponse hydrologique d'un petit bassin versant agroforestier du nord-ouest de l'Espagne (bassin versant de Corbeira, 16 km 2 ) est analysée, avec un accent particulier sur les événements pluvieux. Cinquante-quatre événements pluie-débit, de décembre 2004 à septembre 2007, ont été utilisés pour analyser les traits hydrologiques principaux et montrer quels facteurs expliquent le mieux la réponse hydrologique. La non-linéarité entre les pluies et le ruissellement montre que la variabilité de la réponse hydrologique du bassin versant est liée à la dynamique saisonnière de la pluie et, dans une moindre mesure, à l'évapotranspiration. Le coefficient de ruissellement, estimé comme le rapport entre le volume de ruissellement direct et celui des pluies, sur une base événementielle, a été analysé en fonction des caractéristiques des pluies (quantité et intensité) et les conditions initiales des états du bassin avant événement, telles que l'écoulement de base pré-événement et l'indice des pluies antérieures. Les résultats ont révélé que la réponse hydrologique dépend à la fois des conditions d'humidité du sol au début de l'événement (indirectement déduites de l'écoulement de base au début de chaque épisode de pluie) et de la quantité de pluie, tandis que l'intensité des précipitations n'a présenté une corrélation significative qu'avec les in...

Terraces are a common Mediterranean feature influencing soils, slopes and subsurface hydrology; however, little is known about their impact on hydrological processes, especially in humid regions. This work studied hydrological and erosion processes in the “águas de lima” terrace system common in northwestern Iberia, characterized by wet season irrigation to keep soils saturated and avoid frost on winter pastures. Soil moisture, vegetation height, runoff and sediment yield were monitored for a terraced field in northern Portugal during 19 months. Relationships between rainfall, soil, vegetation, runoff and erosion were analyzed for 49 rainfall events, and within‐storm patterns of soil moisture and runoff were further evaluated for the 12 largest events. Monitoring included two wet seasons with 1264 and 951‐mm rainfall. Runoff followed rainfall with 20 · 5 and 3 · 8 mm, and was mostly related with event and pre‐event rainfall. Combined with hydrograph analysis, this indicated a dominance of saturation‐excess runoff generation, probably related with the presence of a shallow water table caused by limited drainage and constant irrigation during winter. Rill erosion was only observed as a result of run‐on from the irrigation network. Sediment yield was low, 0 · 01 and 0 · 02 Mg ha−1 in the first and second year, and related with runoff, but vegetation cover was found to limit sediment concentration. This work indicates that “águas de lima” terraces promote saturation, runoff generation and a small amount of sediment yield which does not appear relevant for soil conservation. Further work is needed to better understand and conceptualize these processes. Copyright © 2016 John Wiley & Sons, Ltd.

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