Regional runoff prediction through aggregation of first-order hydrological process knowledge: a case study

Abstract

The dominant processes concept was used to develop a regionally applicable rainfall-runoff model. The first-order runoff processes are identified through a combination of field investigations, physico-geographical analysis of the research area, the Alzette River basin in the Grand-Duchy of Luxembourg, and discharge data series analysis. Lithology appeared to be the major source of discrepancy in hydrological behaviour over the total area. As a result, the hydrological behaviour of each lithological substratum was characterized and conceptualized into a parsimonious model structure. The runoff signals were calibrated against the hourly-recorded discharge series of eight sub-basins, with parameter sensitivity and correlation analysis outlining the need for minor corrections to the model structure. Validation against another set of 10 sub-basins showed good results for the regional parameter set, with an average loss in efficiency (R eff ) of 0.04, compared to the reference model, with a mean R eff of 0.79. Due to an up-scaling effect, inducing variations in the dominance of particular runoff processes, some anomalies were found in the performance of individual runoff characteristics. In this respect, limiting the application of the model to a certain spatial scale gives a high reliability of the prediction of the dynamics of hourly runoff in ungauged basins within the study area.Modélisation régionalisée des débits au moyen de l'aggrégation de connaissances sur les processus hydrologiques de premier ordre : une étude de cas Résumé Le concept des processus dominants a été utilisé afin de développer un modèle pluie-débit au champ d'application régional. Les processus d'écoulement de premier ordre sont identifiés à travers un ensemble d'expérimentations sur le terrain, une analyse des caractéristiques physio-géographiques de la zone d'étude, à savoir le bassin de l'Alzette au Grand-Duché de Luxembourg, ainsi qu'une analyse de séries de débits. La lithologie est l'origine principale des différences de comportement hydrologique sur la zone d'étude. Ainsi, le fonctionnement hydrologique propre à chaque substrat géologique a été caractérisé et conceptualisé dans une structure de modèle parcimonieux. Les paramètres des modèles ont été calés au moyen de séries de débits horaires issus de huit sous-bassins. L'analyse de sensibilité des paramètres et l'examen des liens entre ces paramètres ont mis en évidence l'intérêt de corrections mineures sur la structure initiale du modèle pour une application régionale. La validation sur un deuxième lot de 10 sous-bassins a donné de bons résultats pour le jeu de paramètres régionalisé. Le passage d'une échelle spatiale à une autre modifie la prédominance des processus. Ceci explique les moindres performances des modèles sur certains bassins versants. En conséquence, il est conseillé de limiter l'application du modèle à une échelle spatiale donnée pour garantir une prévision fiable de la dynamique de l'écoulement horaire dans des bassins versants non-jaugés à l'intérieur de la zone d'étu...

Elements of a flexible approach for conceptual hydrological modeling: 2. Application and experimental insights

“…The Alzette region is characterized by a heterogeneous geological substratum, which strongly influences its response behavior. A summary of the catchments' climatology and hydrogeology is as follows (see Table 1 and van den Bos et al [2006a, 2006b], for further details).…”

“…However, at the soil‐bedrock interface, where a well‐developed weathered zone is present, the fractured schist formation, in combination with the irregular shape of the bedrock topography, generates local reservoirs where water can be stored. When saturated, this flow network can support subsurface lateral flow [e.g., van den Bos et al , 2006b]. The sandstone formation, in contrast to marls and schist, is highly permeable and supplies a groundwater component during dry weather periods.…”

Impact of temporal data resolution on parameter inference and model identification in conceptual hydrological modeling: Insights from an experimental catchment

“…The study area for this investigation is the 0.47 km 2 Weierbach catchment in the Grand Duchy of Luxembourg. It has a history of experimental work that is providing both high‐resolution rainfall‐runoff‐evapotranspiration time series and also valuable process‐oriented insights into its geomorphology and dominant hydrological dynamics [e.g., van den Bos et al , 2006b; Pfister et al , 2006; Martinez‐Carreras et al , 2010]. The Weierbach is largely forested (85%), with some agriculture on its plateaus (15%); its elevations range from 422 to 512 m above sea level.…”

“…Despite its small size, the catchment has complex hydrologic dynamics, characterized by thresholds and delays operating over a spectrum of time scales. In particular, its streamflow response to a rainfall event in the wet (winter) season is often characterized by two distinct peaks with markedly different time scales [ van den Bos et al , 2006b]. The initial response is near concomitant with the rainfall event and, unless masked by rainfall variability, appears as a spiky first peak in the hydrograph.…”

“…It has been attributed to rainfall over the near‐stream riparian zone, which in the Weierbach catchment comprises rock outcrops and is generally saturated over most of the year. The delayed response generally takes the form of a broader second peak that reaches its maximum at a lag of approximately 48 h. It appears to be sustained by water flows at the soil‐bedrock interface [ van den Bos et al , 2006b]. It can be hypothesized that this delay arises from a cascade of water reservoirs in cracks formed by the irregular bedrock topography.…”