1,721,164 research outputs found
PUB in Quebec: A robust geomorphology-based deconvolution-reconvolution framework for the spatial transposition of hydrographs
No full textISI Document Delivery No.: HO1YUTimes Cited: 0Cited Reference Count: 72Ecrepont, Stephane Cudennec, Christophe Anctil, Francois Jaffrezic, Anne0Elsevier science bvAmsterdam1879-2707The flexibility and parsimony of transpositioning hydrographs using geomorphology-based deconvolution-reconvolution frameworks is particularly adapted to prediction in ungauged basins. Although already tested in semi-arid and oceanic-temperate hydro-climates, its predictions must be reproducible in a variety of hydrological contexts. The present study explores the nivo-pluvial hydrological regime using geomorphology-based hydrograph transposition between 21 gauged catchments ranging from 1.1 to 4466.4 km(2) in Quebec, Canada, and constitutes a case study in prediction in ungauged basins. Three metrics were used to assess model performance for each donor-target pair: Nash Sutcliffe Efficiency (NSE), NSE calculated for the square root of discharge (NSEsqrt), and Volumetric Efficiency (VE). The classic transposition of hydrographs using the specific discharge ratio, used as a reference, was almost always outperformed by the geomorphology-based approach. Good but seasonally variable performance values were obtained for several pairs of catchments, revealing simultaneous structural and circumstancial effects. The difference in size, the physical distance between the gauged donor and its target ungauged catchment, and the season influenced the performance of the geomorphology-based transposition
Evaluation of potential evapotranspiration assessment methods for hydrological modelling with SWAT—Application in data-scarce rural Tunisia
No full textAgric. Water Manage. ISI Document Delivery No.: DS2JL Times Cited: 0 Cited Reference Count: 39 Aouissi, Jalel Benabdallah, Sihem Chabaane, Zohra Lili Cudennec, Christophe International Conference on Water Resources and Environment (WRE) Jul 25-28, 2015 Beijing, PEOPLES R CHINA Elsevier science bv Amsterdam Si 1International audiencePotential evapotranspiration (PET) is an important factor used in hydrological models as well as in management of irrigation projects and water-balance estimations. At the catchment level, hydrological models first calculate PET and then actual evapotranspiration (ET) by considering soil moisture and land use. In this study, we used the SWAT model to estimate PET, actual ET and streamflow. SWAT provides three methods for computing PET: (i) Penman-Monteith (PM), (ii) Hargreaves (HA) and (iii) Priestly-Taylor (PT). Due to missing weather parameters for the PM method, a statistical weather generator embedded in SWAT, WXGEN was used in several studies to generate missing weather data and to fill in gaps in measured records. The goals of this work were to evaluate the PM method’s accuracy in calculating PET using generated and measured meteorological data and further to compare the three embedded methods in SWAT to predict PET. The model was applied to the Joumine basin, covering an area of 418 km2, located in northern Tunisia. For each run, simulated streamflow was compared with measured data by calculating Nash-Sutcliffe efficiency, root mean square error and coefficient of determination. The PM method predicted PET well with generated data. The method used to calculate PET did not considerably affect stream flow predictions; however, significant differences were found among them. Model predictions of streamflow were close to observed values, with a Nash-Sutcliffe efficiency of 0.90 and R2 value of 0.92after monthly calibration using HA method. During the validation period, SWAT predictions were nearly as accurate, with Nash-Sutcliffe efficiency and R2 values of 0.89 and 0.92, respectively
Contrasting behaviour of two riparian wetlands in relation to their location in the hydrographic network
No full textISI Document Delivery No.: 815IETimes Cited: 0Cited Reference Count: 62Montreuil, Olivier Cudennec, Christophe Merot, PhilippeELSEVIER SCIENCE BVAlthough many studies have focused on the hydrological behaviour and classification of wetlands, the wide diversity of wetlands makes a clear and operational view difficult. The objective of this work is to compare the organisation and behaviour of two riparian wetlands (RWs) located, respectively, along Strahler order-2 and order-5 streams of the Scorff River catchment (Brittany, France). Groundwater table dynamics were monitored at the RWs during one hydrological year. Hydrochemistry was characterised during hydrological periods of high and low hydraulic head. The results show clearly the contrast in geomorphological and pedological organisation between the two RWs. In addition, the RW along an order-2 stream exhibited a strong hydrological connectivity with the adjacent hillslope whereas the RW along an order-5 stream showed a strong hydrological connectivity with the adjacent stream. We also observed the contrast between conditions favourable for high and permanent denitrification but on low nitrogen fluxes for order 2, and conditions less favourable to denitrification but on strong nitrogen fluxes for order 5. The relation between the contrasting hydrological and hydrochemical behaviour of these two RWs and their stream orders is discussed from the literature and local observations of the catchment. The results support the hypothesis of a relation between stream order and the hydrological and hydrochemical behaviour of the RWs and thus a catchment-scale organisation which may be taken into consideration in management strategies
Natural streamflow simulation for two largest river basins in Poland: A baseline for identification of flow alterations
Full text linkThe objective of this study was to apply a previously developed large-scale and high-resolution SWAT model of the Vistula and the Odra basins, calibrated with the focus of natural flow simulation, in order to assess the impact of three different dam reservoirs on streamflow using the Indicators of Hydrologic Alteration (IHA). A tailored spatial calibration approach was designed, in which calibration was focused on a large set of relatively small non-nested sub-catchments with semi-natural flow regime. These were classified into calibration clusters based on the flow statistics similarity. After performing calibration and validation that gave overall positive results, the calibrated parameter values were transferred to the remaining part of the basins using an approach based on hydrological similarity of donor and target catchments. The calibrated model was applied in three case studies with the purpose of assessing the effect of dam reservoirs (Włocławek, Siemianówka and Czorsztyn Reservoirs) on streamflow alteration. Both the assessment based on gauged streamflow (Before-After design) and the one based on simulated natural streamflow showed large alterations in selected flow statistics related to magnitude, duration, high and low flow pulses and rate of change. Some benefits of using a large-scale and high-resolution hydrological model for the assessment of streamflow alteration include: (1) providing an alternative or complementary approach to the classical Before-After designs, (2) isolating the climate variability effect from the dam (or any other source of alteration) effect, (3) providing a practical tool that can be applied at a range of spatial scales over large area such as a country, in a uniform way. Thus, presented approach can be applied for designing more natural flow regimes, which is crucial for river and floodplain ecosystem restoration in the context of the European Union's policy on environmental flows
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Scaling, spatial organization and geomorphologic structure analysis for the simulation of hydrologicaland hydrochemical fluxes in ungauged catchment
No full textLa connaissance des dynamiques hydrologiques et du transport chimique associé est indispensable à la mise en place de stratégies de gestion de l’eau et du territoire, mais elle est difficile à consolider pour tous les exutoires de bassins versants porteurs d’enjeux car ils sont souvent « non-jaugés ». A partir d’un hydrogramme observé à l’exutoire d’un bassin jaugé, l'inversion d’un modèle hydrologique à base géomorphologique rend accessible la variable pluie nette en pied de versant. Cette variable indépendante d'échelle est ensuite transposée vers un bassin non-jaugé similaire et reconvoluée en hydrogramme à son exutoire. Cette méthode de "transposition d'hydrogramme", est appliquée pour la première fois en régime pluvio-nival dans 21 bassins Québécois. Le succès de la simulation pour le couple de bassins « jaugé » et « non-jaugé » est conditionné par la similarité hydrologique, soit l’ensemble des caractéristiques assurant un fonctionnement proche entre bassins versants. Nous testons si la composition chimique de l’eau est susceptible de révéler cette similarité à l’aide d’une analyse de type spectral développée sur l’ouest de la France, à l’échelle synoptique. Des groupes de bassins versants se démarquent par une homogénéité / hétérogénéité spatiale des faciès de concentrations, et de l’aire à partir de laquelle est observée la stabilisation de ce faciès. Ceci suggère que la composition chimique des rivières est informative d’un fonctionnement hydrologique similaire. Cette hypothèse est ensuite validée grâce à la transposition avec succès sur six bassins de méso-échelle des hydrogrammes et des relations concentrationdébit (CQ), les meilleurs résultats étant obtenus lorsque le couple respecte une similarité hydrochimique. Enfin, le couplage des hydrogrammes et des relations CQ a permis de prédire efficacement, grâce au principe de similarité, les flux en bassin versant non-jaugé, au pas de temps de 15 minutes.The knowledge of hydrological and hydrochemical dynamics is essential for policy makers to develop appropriate policies of remediation, but this goal is hard to achieve in « ungauged catchments ». Through the inversion of a geomorphology-based hydrological modelling, the net rainfall entering the stream network is assessed from a gauged catchment. This net rainfall is scale independant and can be convoluted in another (ungauged) catchment. This method is applied for the first time in a pluvio-nival context on 21 catchments from Québec. Success of the simulation depends of the hydrological similarity between gauged and ungauged catchments, which is defined as the ensemble of caracteristics insuring a close functionning. We test how riverwater chemical composition reveals this similarity through a synoptic spectral analysis developped on western France. Groups of catchments are identified by their spatial homogeneity/heterogeneoty of the hydrochemical facies, and the area at which hydrochemical stabilisation occurs. This result suggest that riverwater chemical composition is informative of a hydrological similarity. This hypothesis is successfully tested on six mesoscale catchments, by transposing hydrographs and concentration discharge relatioships (CQ), best transpositions are associated to similar catchments. Finally, the coupling of hydrological simulation to CQ curves allowed the prediction of hydrochemical fluxes in ungauged catchments with a 15 minutes timestep
- …
