Stochastic dual dynamic programming (SDDP) is one of the few available algorithms to optimize the operating policies of large‐scale hydropower systems. This paper presents a variant, called SDDPX, in which exogenous hydrologic variables, such as snow water equivalent and/or sea surface temperature, are included in the state space vector together with the traditional (endogenous) variables, i.e., past inflows. A reoptimization procedure is also proposed in which SDDPX‐derived benefit‐to‐go functions are employed within a simulation carried out over the historical record of both the endogenous and exogenous hydrologic variables. In SDDPX, release policies are now a function of storages, past inflows, and relevant exogenous variables that potentially capture more complex hydrological processes than those found in traditional SDDP formulations. To illustrate the potential gain associated with the use of exogenous variables when operating a multireservoir system, the 3,137 MW hydropower system of Rio Tinto (RT) located in the Saguenay‐Lac‐St‐Jean River Basin in Quebec (Canada) is used as a case study. The performance of the system is assessed for various combinations of hydrologic state variables, ranging from the simple lag‐one autoregressive model to more complex formulations involving past inflows, snow water equivalent, and winter precipitation.
<p>The development of Senegal River basin involves trading-off competing objectives in an uncertain environment. Through a stochastic analysis, the trade-off discovery can be enriched to identify vulnerabilities; that is, the sensitivity of those losses with respect to changing natural and anthropogenic factors. In the Senegal River basin, the availability of water at a particular point in space and time is directly linked to both the hydrologic processes and the level of development of the water resources system. Our analysis of the trade-off relationships reveals the existence of two coalitions of objectives: traditional food production (agriculture and floodplain fisheries) versus hydropower-navigation. In terms of vulnerability, the examination of probabilistic trade-offs also shows that of the two main coalitions of objectives, the one dealing with traditional food production is much more vulnerable to changes in both hydro-climatic conditions and allocation policies. Of interest is the fact that the first coalition mostly concerns downstream riparian countries while hydropower, and to a less extent, navigation concern upstream countries. The result is a reinforced power asymmetry where vulnerable downstream riverine communities compete for water with politically and/or economically more powerful upstream water users like power companies.</p>
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