A one‐dimensional process‐based approach to study reservoir sediment dynamics during management operations

Abstract

A comprehensive understanding of the dynamics of erosion and sedimentation in reservoirs under different management conditions is required to anticipate sedimentation issues and implement effective sediment management strategies. This paper describes a unique approach combining fluvial geomorphology tools and morphodynamic modeling for analyzing the sediment dynamics of an elongated hydropower reservoir subjected to management operations: the Génissiat Reservoir on the Rhône River. Functional sub‐reaches representative of the reservoir morphodynamics were delineated by adapting natural river segmentation methods to elongated reservoirs. The segmentation revealed the link between the spatial and temporal reservoir changes and the variability of longitudinal flow conditions during reservoir management operations. An innovative modeling strategy, incorporating the reservoir segmentation into two sediment transport codes, was implemented to simulate the dynamics of erosion and sedimentation at the reach scale during historic events. One code used a bedload approach, based on the Exner equation with a transport capacity formula, and the other used a suspended load approach based on the advection–dispersion equation. This strategy provided a fair quantification of the dynamics of erosion and sedimentation at the reach scale during different management operations. This study showed that the reservoir morphodynamics is controlled by bedload transport in upper reaches, graded suspended load transport of sand in middle reaches and suspended load transport of fine sediments in lower reaches. Eventually, it allowed a better understanding of the impact of dam management on sediment dynamics. Copyright © 2017 John Wiley & Sons, Ltd.

Tackling reservoir siltation by controlled sediment flushing: Impact on downstream fauna and related management issues

“…For instance, at SR, where a downstream area of particular interest deserved special attention, the threshold concerning SSC AVE (1.5 g L -1 ) was coupled to a further alert threshold (3 g L -1 ), requiring revision or interruption of the ongoing flushing activity [30]. A multiple thresholds approach was also implemented at the Génissiat Reservoir (Rhône River, France), one of the few reservoirs at global scale where CSFO is performed and documented in the literature [38–39]. There, the SSC threshold for the entire operation (5 g L -1 , ED around 10 days) is complemented by further restrictions (10 g L -1 and 15 g L -1 for maximum continuous periods of 6 and 0.5 hours, respectively) [40].…”

“…Meile et al [49] for ten events at Gebidem Reservoir (b), from 2004 to 2013. Peteuil et al [40] and Guertault et al [39] for two events at Génissiat Reservoir, in 2003 and 2012.…”

Selecting geomorphic variables for automatic river segmentation: Trade-offs between information gained and effort required

“…However, in recent years, automatic segmentation procedures using geographic tools and statistical methods have been developed that provide more objective and replicable results in defining discreteness along the river continuum (Piégay et al, 2012). These automatic procedures identify longitudinal discontinuities through the river network according to statistically significant variations in certain variables, and can be univariate, based on one single variable (e.g., Leviandier et al, 2012;Parker et al, 2012;Guertault et al, 2018), or multivariate, based on several variables considered simultaneously (e.g., Orlowski et al, 1993;Brenden et al, 2008;Bizzi and Lerner, 2012;Schmitt et al, 2014;Martínez-Fernández et al, 2016b). The number of variables potentially used in multivariate segmentation procedures has increased considerably due to the overwhelming availability of information and the continuing increase in the number of new sophisticated tools and data mining techniques (see Piégay, 2012, Demarchi et al, 2017;Rivas Casado et al, 2017).…”

Réévaluation des apports moyens de matières en suspension de l'Arve au Rhône

“…Une évaluation fiable de ses apports moyens est donc cruciale pour connaître les flux de contaminants particulaires et pour optimiser la gestion des flux sédimentaires à travers les aménagements hydro-électriques du Rhône en aval de l'Arve. La sédimentation est un enjeu particulièrement important pour la retenue de Verbois, dont l'envasement augmente fortement le risque d'inondation dans les bas quartiers de Genève, ainsi que pour la retenue de Génissiat, qui retient une partie du flux sédimentaire lors des opérations de chasse des barrages suisses (Guertault et al, 2018). Cette question est au coeur de la recherche de modalités de gestion des flux alternatives aux chasses périodiques.…”