Application of dynamic programming for the analysis of complex water resources systems : a case study on the Mahaweli River basin development in Sri Lanka

The technique of Stochastic Dynamic Programming (SDP) is ideally suited for operation policy analyses of water resources systems. However SDP has a major drawback which is appropriately termed as its "curse of dimensionality".Aggregation/Disaggregation techniques based on SDP and simulation are presented to analyze a complex water resources system. The system under consideration serves two major purposes: hydropower generation and irrigation. The identification of subsystems by their functional and physical characteristics was an important first step in the analysis. Subsequently each subsystem is represented by a hypothetical composite reservoir to arrive at an operation policy for the interface point of the subsystems. A more detailed analysis which considers the real configurations of the subsystems is performed by following this operation policy of the interface point. Two approaches: sequential optimization and iterative optimization are presented. In these approaches, each subsystem is individually analyzed using two-reservoir SDP models.The applicability of an Implicit Stochastic Approach in which the operation of the system is optimized for a number of deterministic hydrologic data series is also investigated. To complement the aggregation technique of the Composite Reservoir, subsequent disaggregation techniques are proposed. Three different techniques: (1) A statistical disaggregation, (2) An optimization/simulation-based technique, and (3) The disaggregation of the composite policy in the actual operation by incorporating a single-time-step optimization are tested.The accuracy of the sequential and iterative optimization approaches are evaluated by applying them to a subsystem of three reservoirs in a cascade for which the deterministic optimum pattern is also determined by an Incremental Dynamic Programming (IDP) model. In the case of the Implicit Stochastic Approach, the results are compared with the results of the explicit SDP approach and the deterministic optimum operation pattern, in addition to the historical operation pattern of the system. The results of the Composite Policy Disaggregation techniques are compared to the results obtained by real multireservoir optimizations carried out by the use of explicit SDP models

Stakeholder preference elicitation and modelling in multi-criteria decision analysis - A case study on urban water supply

Integration of multiple objectives to evaluate the alternative operating rules for urban water supply reservoir systems can be effectively accomplished by multi-criteria decision aid techniques, where preference elicitation and modelling plays an important role. This paper describes a preference elicitation and modelling procedure involving the multi-criteria outranking method PROMETHEE in evaluating these alternative operating rules. The Melbourne water supply system was considered as the case study. Eight performance measures (PMs) were identified under four main objectives to evaluate the system performance under alternative operating rules. Three major hypothetical stakeholder groups namely, resource managers, water users, and environmental interest groups were considered in decision-making. An interviewer-assisted questionnaire survey was used to derive the preference functions and weights of the PMs. The evaluation of alternative operating rules is not covered in this paper, rather an approach to elicit and model stakeholder preferences in decision-making is described.Multiple criteria analysis Stakeholder preference elicitation Urban water supply systems