Publication
Repeated failures as well as difficulties related to the implementation of new hydroelectric powerplants in industrialized countries illustrate the paradigm evolution which manages relationship between human society and nature. Problems resulting from these plants, often ignored during planning phases, in addition to the current trend to restore a natural state, require ecological analyses for new constructions as well as for scheme restoration or river corrections. Taking into account energy and ecology, together with security, financial and socio-economical aspects, transforms the design of hydraulic schemes into complex problems. Designing, dimensioning and managing in an integrated way such multipurpose hydraulic schemes thus require new approaches. The first objective of the present work is the comprehension of the complex system formed by a multipurpose hydraulic scheme and the determination of its most important characteristics. The second objective aims at developing a methodology to quantify the installation impacts on the key factors of the system. The third objective is an optimization of the system itself as well as the determination of the distribution of the cost between the various purposes. The developed methodology first includes a qualitative analysis of the system which then allows a quantitative modelling. Optimization is carried out on the basis of this second modelling. The cost distribution is finally obtained by comparison of partial optimizations of the system. The qualitative analysis is carried out starting from the method developed by Gomez and Probst (1995) which is based on a cognitive representation in order to model the complex system behavior. This representation includes feedback loops between the various factors. The mathematical analysis of the network classifies these factors and highlights the most important ones (key factors). In the particular case of the multipurpose run-of-river hydroelectric scheme, this method distinguishes the decisional level from the functional level. It underlines the variable, namely the downstream flow, which constitutes the bond between the two levels. The purposes of this project are to reduce hydropeaking, to produce energy, to offer a retention volume for flood mitigation and to allow a social use for leisure activities. Quantitative modelling is carried out by simulation models, considering an optimized operation of the reservoir which determines the downstream flow. This optimization is performed by a mathematical resolution using the software AMPL. It includes the constraints to reduce the downstream flow variations with the objective of maximizing energy production. It also results in minimal reservoir water level variations. The simulation models then calculate the scheme behaviors (hydraulic, energy, thermal, ecological, social and financial). The flood management is treated separately, with the objective of reducing the flood peak by preventive draining of the reservoir
François Maréchal, Daniel Alexander Florez Orrego, Meire Ellen Gorete Ribeiro Domingos, Réginald Germanier