André Musy

Uncertainty in hydrograph separations based on geochemical mixing models

A detailed uncertainty analysis of three-component mixing models based on the Haute–Mentue watershed (Switzerland) is presented. Two types of uncertainty are distinguished: the ‘model uncertainty’, which is affected by model assumptions, and the ‘statistical uncertainty’, which is due to temporal and spatial variability of chemical tracer concentrations of components. The statistical uncertainty is studied using a Monte Carlo procedure. The model uncertainty is investigated by the comparison of four different mixing models all based on the same tracers but considering for each component alternative hypotheses about their concentration and their spatio-temporal variability. This analysis indicates that despite the uncertainty, the flow sources, which generate the stream flow are clearly identified at the catchments scale by the application of the mixing model. However, the precision and the coherence of hydrograph separations can be improved by taking into account any available information about the temporal and spatial variability of component chemical concentrations.

Generalization of TOPMODEL for a power law transmissivity profile

Keywords: Hydrologie Reference HYDRAM-ARTICLE-1997-003doi:10.1002/(SICI)1099-1085(199707)11:9 3.0.CO;2-UView record in Web of Science Record created on 2005-10-11, modified on 2016-08-08

Coupling 1D Monte-Carlo simulations and geostatistics to assess groundwater vulnerability to pesticide contamination on a regional scale

Abstract A method to predict groundwater vulnerability to pesticide contamination on a regional scale has been developed and applied to a part of the upper Rhone river valley in Western Switzerland. Stochastic application of deterministic pesticide leaching models (Monte-Carlo), along with geostatistical interpolation techniques, were used to map both vulnerability levels and uncertainties. The various tested leaching models (numerical and analytical solutions of the convection–dispersion equation, capacitive model) lead to similar outcomes. The resulting maps show very high vulnerabilities. However, uncertainties are large, ranging from 20–30% for vulnerability indices between 0 and 1. Variations in pesticide properties (40–50%), water table depth (30–40%) and organic carbon content (20%) account for almost all the uncertainties on predicted contamination levels.

Flow, mixing, and displacement in using a data‐based hydrochemical model to predict conservative tracer data

We extend the data-based hydrochemical model of Iorgulescu et al. (2005), able to simulate discharge and reactive chemical tracer concentrations (silica and calcium) in streamflow for subcatchments of the Haute-Mentue research basin (Switzerland), to the prediction of additional δ 18O values treated as a conservative tracer. The hydrochemical model is based on a parameterization of three runoff components (direct precipitation (DP), acid soil water (AS), and deep groundwater (GW)) in a chemical mixing model. Each component is modeled through an identical structure consisting of a nonlinear gain and a linear transfer function with two reservoirs (fast/slow) in parallel having a constant partition between them. We formulate a set of hypotheses concerning the isotope characterization of each component to provide additional information about how new rainfall inputs are processed in the hydrological response of the catchment. In particular, the AS component is modeled through a nested structure of hypotheses (models) of increasing complexity. It will be shown that hydrological processes in the hillslope associated with the DP, AS, and GW components are especially effective in filtering of higher-frequency fluctuations in precipitation isotopic ratios at the intraevent, interevent/seasonal, and annual/multiannual timescales. The highly nonlinear and nonstationary AS component represents predominantly “recent” water stored in the upper decimeters of the soil profile. Results also suggest that subsurface pathways are significant for the DP component. A local flow path mechanism is proposed for explaining the large fluxes of subsurface flows.

Two‐site modeling of rainfall based on the Neyman‐Scott process

On the basis of the Neyman-Scott process a model is proposed to generate rainfall at two sites simultaneously. This model takes into account the correlation, which is produced by generating bivariate correlated variates. The cross correlation between the sites has been computed in order to estimate the parameters. Finally, the model is validated for three pairs of stations situated in the Swiss Plateau region.

Introducing SMURF : A software system for monitoring urban functionalities

Urban land-use planning and management are in constant mutation throughout the world. With sustainability as a goal, the use of participative GIS is becoming more and more in demand. Given the willingness of local authorities to test participatory models and instruments, this paper presents an original implementation of information and communication technologies to support public participation. A system for monitoring urban functionalities (SMURF) was created for supporting participatory planning and management in African cities. The software instrument consists of a geographic database and of spatial indicators, for sharing information, editing information, and evaluating city development. To collect and update data, the model begins with the gathering of the data from each stakeholder, who, in return, gets a better knowledge of the land and a planning support tool. However, the implementation of these technologies presents several challenges: create an adapted interface, elaborate a relevant set of data and indicators, manage the data, and institutionalize the instrument. After an introductory presentation of the context and use of information technologies for the management of African cities, this paper focuses on SMURF and its components. It then shows the experimental application of the software in the city of Thies, Senegal, before concluding with a more general discussion on the relationship between technology, information, knowledge, and participation.

Predictive Hydrology: A Frequency Analysis Approach

The unusual frequency of hydro-meteorological events in recent decades, often with catastrophic consequences for society and the environment, require new methods for designing water management projects and the structures meant to protect us from natural hazards. These methods and techniques are often based on the statistical modeling techniques of frequency analysis. Predictive Hydrology: A Frequency Analysis Approach is the first book to address both the theoretical concepts and the methodological approaches used in frequency hydrology—spelling out the fundamental methods to consider, providing concise instruction on the techniques that are involved, and including examples and critiques based on practical applications. It explores some of the recent research developments in the field. Published originally in French, this English translation targets students in civil engineering, environmental sciences and technology, hydrology, geography, geology and ecology. This book will also serve as a useful reference not only for teachers and researchers, but for engineering practitioners, who are constantly faced with the problems of handling data, but often find themselves without the appropriate analytical tools.

A geomorphologic kinematic-wave (GKW) model for estimation of floods from small alpine watersheds

Keywords: Hydrologie Reference HYDRAM-ARTICLE-1999-004 Record created on 2005-10-11, modified on 2016-08-08

A geomorphologic non-linear cascade (GNC) model for estimation of floods from small alpine watersheds

Abstract A geomorphologic non-linear cascade (GNC) model was developed for simulation of extreme floods from small alpine catchments. The GNC model couples the classical cascade of storage reservoirs and the geomorphologic representation of the catchment based on the Horton-Strahler ordering scheme. The model was applied to a number of floods events from two small alpine catchments in Switzerland, and the agreement between simulated and observed flood events was good. The physical meaning of the model parameters to be calibrated remains unclear, however, and more work is needed in this regard.

A simple formula to calculate the width of hydrological buffer zones between drained agricultural plots and nature reserve areas

This paper presents new formulae to calculate the width of a buffer zone between a drained agricultural plot and a nature reserve area. These formulae are based on the classical Dupuit-Forchheimer assumptions and take into account the position of the impervious layer. With basic meteorological and agrological inputs, the proposed equations can be used to determine the length of the depression zone during watertable drawdown due to underground drainage. Calculating the required width of ‘protection belts’ around peatland reserves is a typical and common application of the formulas presented in this paper.