Journal of Water Resources Planning and Management

Implementing risk-based Great Lakes water level management and forecasting, as recommended by the International Joint Commission, would allow managers and other interests affected by fluctuating water levels to consider the wide range of potential future lake levels, incorporate some of the uncertainty inherent in forecasts, and allow explicit consideration of risk. Decision making that requires knowledge of future lake levels would potentially improve, resulting in economic and environmental benefits. Significant institutional and technical barriers preventing implementation exist, among them the lack of International Joint Commission authority to mandate other agencies to implement its recommendations, and the lack of objective evidence that risk-based water level management is an improvement over current procedures. Strategies for overcoming these and other barriers are suggested. The barriers and strategies specific to this case study are generalized so that other water resource managers may consider them when applying risk-based management to their systems.

Environmental and socioeconomic indicators are selected to study the impacts of global warming on the water resources of the United States. One of the indicators, regional reservoir storage vulnerability, is a particularly useful index summarizing the effectiveness of regional water supply systems to meet demands. A comparison of indicator tabulation and evaluation methods finds that reporting an indicator as a fraction of its stress threshold is most effective. Indicator display methods are compared, and the star diagram proves most effective as a visual aggregation technique. Indicators and evaluation methods are applied to the present climate and to one possible climate change scenario assuming economic growth. It is apparent that the primary impacts of global warming occur in the western U.S. and include (1) fewer relative stresses on hydroelectric systems due to an increase in energy supply from other sources, and (2) more stresses on available water resources due to increases in total withdrawals and, in some cases, decreases in flows. The writers believe that with wise indicator display methods, mathematical aggregation of indicators into indices may be unnecessary.

A general algorithm is presented for determining values for unit cost coefficients that reflect water use priorities for network flow programming models of water resource systems. The overarching principle for setting unit penalties for priority-based operations is that senior unit penalties must exceed the combined junior unit penalties for any feasible competing space-time path through the system for any unit of water potentially available at the senior location. The algorithm accommodates both storage and flow related water uses over multiple periods and accounts for the effects of return flow on flow allocation, which can introduce a complexity that inhibits the use of intuitive or trial-and-error methods for determining cost coefficient values. The approach is formulated initially as a linear program that can be used as a preprocessor to the network flow modeling and is applied to a water-rights model of the Truckee-Carson system. The formulation is generalized for a location connectivity matrix and vector of use priorities.

A simulated annealing-based heuristic has been developed to obtain the least-cost design of a looped water distribution network. A Newton search method was used to solve the hydraulic network equations. Simulated annealing is a stochastic optimization method that can work well for large-scale optimization problems that are cast in discrete or combinatorial form, as with the problem proposed. The results obtained with this approach for networks currently appearing in the literature as case studies in this field (whose solution by other optimization methods was known) have proved the ability of the heuristic to handle this kind of problem.

Immediately following the passage of the Clean Water Act over 25 years ago, there was a need to develop water quality management plans (WQMP) for each watershed. Assimilative capacities and wasteload allocations were quantified using primitive tools because of limited water quality data and the lack of skilled modeling professionals. As the quality of receiving waters improves due to increased treatment of waste flows over the last two decades, existing models require updating or postauditing to continue to support the WQMP. In some cases, as presented here, the quality of the waters always met standards, although an old model predicted nonattainment. This situation indicates that there is a need for increased use of water quality models to review the assimilative capacity of the receiving water for regulatory control and water quality management. Finally, the work presented in this paper demonstrates that modeling continues to be the most cost-effective method of water quality planning and that water resource managers should apply water quality modeling on a regular basis to support the present and future needs of the watershed.

An optimization model for selecting and sizing potential reservoir and hydropower plant sites on river basins is presented. The model improves on the work of Lall and Miller by replacing the modified sequent peak algorithm for sizing reservoirs with a behavior analysis algorithm that allows operation of the reservoir system with realistic operating policies. A heuristic simulation procedure is used to assess the feasibility of developing self-sustainable hydropower plants at each site. A gradient (derivative) based optimization algorithm is employed to integrate these simulations into an optimal screening model. To enhance the efficiency of the algorithm, the approximate and expensive approach of evaluating derivatives by divided differences is replaced by automatic differentiation. A comparison of the computational performance shows that the optimal solution with automatic differentiation is obtained four times faster than with the divided difference method. The model is developed in the context of river basins in India.

This paper uses a hydrologic budget method and partial chemical data to evaluate the availability of ground water for irrigation supply in a humid region through a case study of the Saginaw Bay basin, Mich. Concentrations of chloride are used to evaluate the quality of ground water for irrigation. The results indicate that ground water does not appear to be a reliable source for regional irrigation supply in the study area. The case study demonstrates that the integration of a hydrologic budget and water quality data is an effective approach in the analysis of the limit of ground water for irrigation development in humid regions when intensive hydrogeologic monitoring and modeling are unaffordable.