Journal of Water Resources Planning and Management

Despite the laudable objectives of the International Drinking Water Supply and Sanitation Decade (IDWSSD) launched in 1980, developing countries are still faced with inadequate water supply and poor sanitation in rural and periurban areas. This problem may be attributable to the issue of equity in the provision of water supply and sanitation. In most developing countries, governments still provide water supply and sanitation mostly to urban areas whilst the rural and urban fringes are poorly served. There are case histories of project failures in rural areas due to many factors including choice of inappropriate technology, lack of effective backup support, noninvolvement of user community in the planning and implementation process, and implementation of projects for political gains. In order to solve these problems, the issue of equity should be vigorously pursued in the development of water supply and sanitation projects. A sequential procedure for total involvement of the user community in the planning construction, operation, and maintenance is proposed here to help provide equity.

The explicit consideration of multiple objectives in decision making is becoming increasingly important in water resources systems analysis. Conflicting objectives like irrigation, flood control, hydropower production, and environmental preservation are inevitable while deriving the operating alternatives in an efficient way for any complex water resources system. In this paper, a linear multiobjective programming model has been developed and the constraint technique was used to derive the optimal releases for various purposes from a large‐scale multireservoir system consisting of five reservoirs in India. Maximization of irrigation releases and maximization of hydropower production have been considered as the twin objectives in the model subjected to constraints on physical limitations, environmental restrictions, and storage continuity. This model was applied to three series of inflow sequences representing the normal, drought, and excess‐flow conditions. The tradeoff analysis between the conflicting objectives of irrigation and hydropower production was also carried out and the transformation curve was plotted. The optimal point on this curve gives the best combination of the twin objectives considered in the model.

The utility of optimal‐control theory for the deterministic operation of very large multireservoir systems is demonstrated for a real situation, the complex multireservoir Mahaweli system in Sri Lanka. This system includes 19 nodes, or reservoirs, and 35 release links. The model developed for the Mahaweli is designed to minimize a hydroelectric energy shortage objective and satisfy prespecified irrigation demand constraints. Two alternative approaches are explored for optimal operation of the Mahaweli system. The first involves monthly application of the optimal‐control algorithm to find an optimal policy for the next year, based on current storage and forecasted or historical inflows and demands. The second alternative is an implicit stochastic approach, in which linear operating rules are derived using deterministic optimal control and historical data. Both of the alternatives give reasonable and comparable results. The implicit stochastic optimization alternative has a great advantage regarding computer time and storage requirements. This makes it usable on a small personal computer, providing the system operator with decisions in a few seconds, even with very large systems.

Heated effluent from thermoelectric power stations may adversely affect river ecology if adequate dilution water is not available. If the effluent is discharged to a regulated waterway, however, the adverse water‐quality impacts may be reduced by releases that augment the stream flow in low flow periods. An approach is developed for obtaining reservoir management policies that explicitly consider the dilution needs of downstream thermoelectric power stations. A goal programming model is used to identify these policies. Targets for reservoir storage and power generation are established and the sum of the deviations from these targets is minimized, subject to water‐quality constraints. Additional management policies are identified for reservoirs that are operated in conjunction with alternate cooling systems, namely cooling towers. A mixed‐integer programming model is developed that identifies the optimal periods in which a cooling tower may operate given that the power station may also be cooled with a once‐through cooling system by water withdrawn from a regulated waterway. These models are applied to a realistic case study based on the Shellmouth Reservoir and Dam in southwestern Manitoba, Canada.

The electricity cost of pumping accounts for a large part of the total operating cost for water‐supply networks. This study presents a method based on linear programming for determining an optimal (minimum cost) schedule of pumping on a 24‐hr basis. Both unit and maximum demand electricity charges are considered. Account is taken of the relative efficiencies of the available pumps, the structure of the electricity tariff, the consumer‐demand profile, and the hydraulic characteristics and operational constraints of the network. The use of extended‐period simulation of the network operation in determining the parameters of the linearized network equations and constraints and in studying the optimized network operation is described. An application of the method to an existing network in the United Kingdom is presented, showing that considerable savings are possible. The method was found to be robust and with low computation‐time requirements, and is therefore suitable for real‐time implementation.

A group of optimization models for the real‐time operation of a hydropower system of reservoirs is presented in this paper. The dimensionality problems usually found in dynamic programming formulations are solved by a space‐time aggregation/disaggregation procedure that combines stochastic dynamic programming and linear programming techniques. The reservoirs in a hydropower system are aggregated in power units rather than in water units, and an optimal operating policy for the equivalent aggregated reservoir is found in the first part of this work. The objective function in this first part is to minimize the total cost or energy production for a hydrothermal system. The aggregated policy obtained is used in the real‐time operation of the system to determine the recommended daily releases and power production from each reservoir of the system. The proposed methodology is applied to a case study, the Lower Caroni system in Venezuela, which is composed of four reservoirs in series and a total installed capacity of 17,000 MW, with satisfactory results.

Irrigation was one of the earliest efforts, supplementing agriculture, in the ascent of man. With the recent population explosion, it has become a critical issue in man's survival, and in environmental conservation. Irrigation and drainage, however, continue to be practiced, by and large, in a primitive manner, despite the fact that if the present practice continues, serious food scarcity and environmental degradation may have to be faced. Advances have taken place that can avert this bleak scenario. In this context, some policy issues are discussed, followed by the case study of irrigation and drainage in India. A brief overview of irrigation and drainage is undertaken. Modern systems concepts are used to analyze the policy. Objectives and evaluation criteria are briefly developed, followed by some important technological and environmental issues. An overview of the policy, as it evolved historically in the context of the technological and socioeconomic milieu, is undertaken. Modernization issues are identified. The subject is highlighted by reviewing the scene in India with policy formulation for modernization, with reference to detailed studies.