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This paper investigates whether the calibrated parameter values for two rainfall–runoff models based on historical observed data can be used to reliably predict runoff responses to changes in future climate inputs. Analyses are carried out using historical monthly climate and runoff data from 27 catchments in West and Central Africa. Better performances are obtained when the models are calibrated on a dry period to predict runoff in a wet period. Similarly, it is easier for the models calibrated on a period of large hydroclimatic variability to predict runoff in a period of small hydroclimatic variability than the contrary. This paper tests also the assumption that transferability of rainfall–runoff models, variable hydroclimatic conditions, and local sensitivity of the model parameters can be linked. The inconclusive results still show variability according to the chosen efficiency criteria and selected periods. All these results indicate that the transfer of model parameters from one period to another can introduce a significant error in runoff simulations, which means increased uncertainty in the assessment of impact of climate and environmental changes, an essential question for West and Central Africa.Editeur M.C. Acreman; Editeur associé Gil Mahé [ABSTRACT FROM PUBLISHER]

This paper proposes a methodology for studying the sensitivity and uncertainty of the return period of an annual maximum flood that is partially measured, and of which observation is limited to the water-level trace on the river bed. Two other constraints are considered in the methodological choices. First, maximum discharges recorded during runoff events at the studied hydrological station are not available; only maximum annual discharges are accessible to illustrate the study. Also, the series of maximum annual discharges is short. Thus, the study focuses on mean daily flow series containing a single missing value corresponding to the partially gauged flood of interest. However, because the length of the available most complete mean daily flow series is moderate, a statistical model of Peaks Over Threshold (POT) is adopted. The maximum flow of the partially gauged flood is estimated from the water-level trace of the flood by five computation approaches (extrapolation with statistical regression using hydraulic parameters of the river bed section, two Manning-Strickler models in the homogeneous bed and two in the compound river bed section), using bed roughness coefficients according to the range deduced from previous station observations. We propose to study the statistical distribution of the ratio α of the annual maximum instantaneous flood to the annual maximum daily flow. Thus, the water-level trace on the river bed can be used to complete the series of mean daily runoff using a hypothesis on the value of α. The paper studies the uncertainty on α under various hypotheses of bed roughness. A lognormal distribution is fitted to α and Monte Carlo simulations are performed. A value of the mean daily runoff is further attached to each simulation of α. Fifty (50) runs are generated in every case. The POT model is then applied to every series of mean daily runoff thus obtained, and the quantiles of the mean daily flows for various return periods are estimated according to each series. The variability of simulated quantiles is represented by box-plots and is quantified by the interquartile range. The application concerns a hydrometric station controlling a basin of 9000 km2 in a semi-arid region in North Africa. Observed series are studied for the period 1984–2006 and 114 well-monitored flood events are available to perform the analysis. It is found that the median value of the 50-year mean daily runoff ranges from 1410 to 1840 m3/s depending on the threshold value and the assumption about bed roughness coefficient. The various methods, considering the different values of threshold, provide an interquartile range for the return period of the mean daily flow of this partially gauged flood of between 30 and 70 years. [ABSTRACT FROM AUTHOR]

The strong socio-economic growth of Quito has led to significant projects of inter-basin transfers, intensifying high-altitude resources mobilization in environmentally sensitive areas and with accelerated melting of glaciers. In order to study various future scenarios, we propose modelling of the climate/glacier/hydrology/water resources management continuum, applied to Andean basins. Using the tool Water Evaluation and Planning (WEAP21), we developed: (1) semi-distributed hydro-climate modelling with monthly data using regional homogenization (vector method); (2) glacier modelling of water production and inter-annual evolution; (3) modelling in hydrological units depending on land cover; and (4) water management modelling distinguishing water rights, allocation and use. In this paper, we mainly present results of monthly hydrological calibrations (1963–2006), studying, in particular, the equifinality of various parameter settings. We show flexibility, robustness and limits of the proposed modelling, contributing to identification of uncertainties for evaluation of future scenarios. [ABSTRACT FROM AUTHOR]

The SHYREG method is a flood frequency analysis method that can be applied to any location in the French metropolitan territory for flood risk management. It is based on an hourly stochastic rainfall generator coupled with a simplified distributed rainfall–runoff model. This paper presents the validation of flood frequency estimates made using SHYREG for a wide range of 1605 French catchments. For current return periods (i.e. of up to 10 years), the SHYREG-estimated flood frequency values are consistent with estimates from the generalized extreme value (GEV) distribution based on the Nash-Sutcliffe criterion. For extreme return periods, validation of flood frequency estimates is based on: (a) consistent peak and daily discharges estimated from a long observed flow record; (b) reasonable modelled saturation of the production storage for extreme events; and (c) studying the robustness of the SHYREG method by means of statistical criteria. [ABSTRACT FROM PUBLISHER]

This paper presents a study of the sediment transport in the Wadi Bellah watershed. In order to understand the sedimentation dynamic in the watershed, analysis is based on instantaneous flow data and the concentration of suspended sediments transported in the stream. The results show that the annual average of specific degradation is about 610 t km−2year−1. This value is comparable to those found in other regions with similar hydrologic regimes. Analysis of the evolution of sediment concentration in the stream and the quantification of sediment fluxes showed that the sediment supply occurs mainly during floods. Three periods of active erosion are distinguished, the first, intense in winter, the other two of lesser extent in spring and autumn. [ABSTRACT FROM AUTHOR]