This study is based on 22 gauged sites and 26 poorly gauged sites on the territory of Réunion Island, where quality hydrometric observations are available.
Information on streamflow is crucial for ...good water resources management and for respect ecosystems. For gauged catchments, the hydrology can be investigate from observations. For ungauged catchments, the lack of streamflow observations do not allow it. In this context, regionalized models for rainfall runoff are valuable resources. They have been widely employed as a means of predicting the streamflow of ungauged catchments. However, the performances of regionalized hydrological models seems to depend on the spatial density of available flow gauging networks. Using observations available on poorly gauged catchments to help to regionalize hydrological models can be another way of solving the data scarcity problem. This paper presents a framework for evaluating the use of spot flow measurements in a regionalized hydrological model when performing low flow statistical estimations in ungauged catchments. Three approaches are used to evaluate how to include spots flow measurements in the hydrological model calibration process. We tested too the addition of the poorly gauged sites in the regionalization procedure of the hydrological model. The effectiveness of the methods was measured by cross-validation.
It is found that an increased accuracy using the regionalized model with help from spot flow measurements to predict streamflow time series in ungauged catchments. The increase is more moderate in low flow statistical estimations (QMNA5) than in medium and high flows.
•Evaluate the performance of a parsimonious regionalized hydrological model with the additional poorly gauged catchments.•The approach is applied in river catchments of Réunion Island.•The performance of regionalized model depends on how the spot flow measurements are used to calibrate these catchments.•In ungauged context, the regionalization process using additional poorly gauged catchments show promising results.
Low water levels are a seasonal phenomenon, which can be long, short, and more or less intense, affecting entire watercourses. This phenomenon has become a concern for many countries who seek better ...understanding of the processes that affect it and learn how to optimally manage water resources (pumping, irrigation). Consequently, a lumped rainfall model at daily time step (GR) has been defined, calibrated, and regionalised over French territories. The input data come from SAFRAN, the distributed mesoscale atmospheric analysis system, which provides daily solid and liquid precipitation and temperature data throughout the French territory. This model could be improved, in particular to more accurately simulate the hydrological response of watersheds interacting with groundwater. The idea is to use piezometric data from the ADES bank, available in France, and to use it for the calibration phase of the hydrological model. The analysis was carried out across ten French catchments that are representative of various hydrometeorological behaviours and are located in a diverse hydrogeological context. Each catchment must be represented by a piezometer that closely represents the main aquifer that interacts with the basin. This piezometer is located on part of the watershed that is most covered in terms of its drainage network, and closest to its outlet. Different signal processing methods are used to characterise the relationship between the fluctuation of river flow, piezometric levels and rainfall time series. Potential processing methods will be carried out in the temporal domain. To quantify groundwater table inertia and that of the catchment area, correlograms were calculated from daily chronicles of flows and piezometric levels. A cross-correlatory analysis was set up to see, in more detail, the correlations between the flow rates (especially base flows) and piezometric level time series. This type of analysis makes it possible to study relationships between various observations, and tests were carried out to take this information into account during the phase of the calibration of hydrological model parameters. These different analyses will hopefully help us to use piezometric data to consolidate the quality and robustness of the modelling.
Forest hydrology studies carried out in France have focused mainly on the Mediterranean part of the country. Three experimental catchment groups exist and have been monitored over a long period. Some ...forested catchments (Draix catchment) underwent no change during the study period, while others experienced either clear cutting (Lozère catchment) or forest fires (part of the Réal Collobrier catchments). In each case studied, the behaviour of the forested catchment was compared to that of a control catchment.
Included with the experimental catchment studies are the results of research with a fundamentally different approach. The research is based on a statistical study of the interrelated development of afforestation rates and runoff characteristics for average-sized catchments (around 100
km
2) in that part of the southern French Massif Central which is subject to Mediterranean rainfall conditions.
The results differ considerably from one site to another, indicating the degree of complexity of the rainfall/runoff relationship. An increase in extreme flood events due to forest disturbance could by no means be confirmed in every case. A closer look at the hydrological behaviour of the catchments cleared up the apparent inconsistencies. It is mainly the contrast between bare soil and vegetated soil, rather than between forest and other types of vegetation witch is relevant in explaining the hydrological behaviour.
Much has been written on the subject of objective functions to calibrate rainfall-runoff models. Many studies focus on the best choice for low-flow simulations or different multi-objective purposes. ...Only a few studies, however, investigate objective functions to optimize the simulations of low-flow indices that are important for water management. Here, we test different objective functions, from single objective functions with different discharge transformations or using low-flow indices, to combinations of single objective functions, and we evaluate their robustness and sensitivity to the rainfall-runoff model. We find that the Kling and Gupta efficiency (KGE) applied to a transformation of discharge is inadequate to fulfil all assessment criteria, whereas the mean of the KGE applied to the discharge and the KGE applied to the inverse of the discharge is sufficient. The robustness depends on the climate variability rather than the objective function and the results are insensitive to the model.
EDITOR A. Castellarin; ASSOCIATE EDITOR C. Perrin
Testing hydrological models under changing conditions is essential to evaluate their ability to cope with changing catchments and their suitability for impact studies. With this perspective in mind, ...a workshop dedicated to this issue was held at the 2013 General Assembly of the International Association of Hydrological Sciences (IAHS) in Göteborg, Sweden, in July 2013, during which the results of a common testing experiment were presented. Prior to the workshop, the participants had been invited to test their own models on a common set of basins showing varying conditions specifically set up for the workshop. All these basins experienced changes, either in physical characteristics (e.g. changes in land cover) or climate conditions (e.g. gradual temperature increase). This article presents the motivations and organization of this experiment—that is—the testing (calibration and evaluation) protocol and the common framework of statistical procedures and graphical tools used to assess the model performances. The basins datasets are also briefly introduced (a detailed description is provided in the associated Supplementary material).
Intermittent rivers and ephemeral streams (IRES) are now recognized to support specific freshwater biodiversity and ecosystem services and represent approximately half of the global river network, a ...fraction that is likely to increase in the context of global changes. Despite large research efforts on IRES during the past few decades, there is a need for developing a systemic approach to IRES that considers their hydrological, hydrogeological, hydraulic, ecological, and biogeochemical properties and processes, as well as their interactions with human societies. Thus, we assert that the interdisciplinary approach to ecosystem research promoted by critical zone sciences and socio‐ecology is relevant. These approaches rely on infrastructure—Critical Zone Observatories (CZO) and Long‐Term Socio‐Ecological Research (LTSER) platforms—that are representative of the diversity of IRES (e.g., among climates or types of geology. We illustrate this within the French CZO and LTSER, including their diversity as socio‐ecosystems, and detail human interactions with IRES. These networks are also specialized in the long‐term observations required to detect and measure ecosystem responses of IRES to climate and human forcings despite the delay and buffering effects within ecosystems. The CZO and LTSER platforms also support development of innovative techniques and data analysis methods that can improve characterization of IRES, in particular for monitoring flow regimes, groundwater‐surface water flow, or water biogeochemistry during rewetting. We provide scientific and methodological perspectives for which this interdisciplinary approach and its associated infrastructure would provide relevant and original insights that would help fill knowledge gaps about IRES.
This article is categorized under:
Water and Life > Stresses and Pressures on Ecosystems
Science of Water > Hydrological Processes
Water and Life > Conservation, Management, and Awareness
The Auzon River under dry, low‐flow, and flood conditions (from left to right), which is an intermittent tributary of the Ardèche River (France), and monitored as a site of the ZA Bassin du Rhône (Rhône Bassin LTSER) and of the Mediterranean Hydro‐meteorological Observatory Cévennes‐Vivarais (OHMCV CZO).
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