Journal of Water Resources Planning and Management

Seven ground-water management models were developed to determine the optimal planning and operating policies of a costal aquifer in sourthern Turkey threatened by saltwater intrusion. Steady-state and transient finite-element simulation models, representing the response of the system, are linked to linear and quadratic optimization models using response functions. Optimal pumpage policies were determined for 94 wells under three management objectives that maximized agricultural water withdrawals and minimized drawdowns and pumping costs, subject to constraints related to the system's response equations; demand requirements; drawdown limitation in saltwater intrusion control locations and pumping wells; and discharge bounds. The results are shown in the form of trade-off curves relating optimal pumpage rates and pumping costs to basinwide drawdowns and saltwater containment. Modeling results indicate that significant increases in total aquifer yield are possible with controlled drawdowns so that infringement of saltwater is prevented. Optimal pumping schedules differed, depending on the type of objective function used. The best policy appears to be the one in which the excess water pumped from the most productive wells is transported overland to meet local demands at less productive wells.

Regional flood frequency analysis involves combining extreme-flow information from numerous stations to enhance the reliablity of the temporal characterization of extreme-flow data at sites with short periods of record. The region of influence (ROI) approach used herein, defines regions such that each site has a potentially unique combination of stations. The similarity of the selected stations is ensured by incorporating a homogeneity test into the regionalization process. A hierarchical feature is added to the ROI approach to further enhance the efficiency of the spatial information transfer. This is done by taking advantage of the different spatial similarity scales that have been observed for different orders of moments for a flood frequency distribution. The incorporation of this concept into the ROI framework results in a set of ROIs for a site as opposed to a single ROI. The hierarchical ROI approach is evaluated through the use of a Monte Carlo experiment applied to data representative of a collection of unregulated catchments in the midwest portion of Canada. The simulation experiment shows that an improvement in flood quantile estimation is achieved.

An optimal hydraulic gradient control (OHGC) design involves the joint use of optimization and simulation models. When an imperfect ground-water simulation model is used, the reliability of the OHGC design has to be questioned. One major ground-water modeling error is often introduced in the process of identifying a transmissivity field. The error is caused by parameterization and error in field measurements used to estimate unknown transmissivities. Using computer experiments, this study investigated the effects of parameterization and measurement errors on performance of deterministic OHGC designs. It was found that both parameterization and measurement errors could lead to low reliability of OHGC schemes. The optimal well locations and pumping rates depend on the parameterization scheme implemented and the measurement error magnitude. Although addition of steady-state head measurements can improve the reliability and performance of OHGC schemes in presence of measurement error, such measurements do little to improve reliability in presence of parameterization error. In addition, it is shown that applying a safety margin in a deterministic model is an effective approach to enhancing design reliability and performance when parameterization and measurement errors are present.

A fuzzy rule-based model is constructed to derive operation rules for a multipurpose reservoir. The case study of the Tenkiller Lake in Oklahoma illustrates the methodology. Operation rules are generated on the basis of economic development criteria such as hydropower; municipal; industrial and irrigation demands; flood control and navigation; and environmental criteria such as water quality for fish and wildlife preservation, recreational needs, and downstream flow regulation. The fuzzy rule-based model operates on an “if-then” principle, where the “if” is a vector of fuzzy explanatory variables or premises and “then,” of fuzzy consequences. The reservoir storage level, estimated inflows, and demands are used as the premises and release from the reservoir is taken as the consequence. Split sampling of historical data (mean daily time series of flow, lake level, demands, and releases) is used to train and then validate the rules. Different performance indices are calculated and two figures of merit, namely, engineering sustainability and engineering risk are developed for evaluating the rules generated by the model, which appears to be easy to construct, apply, and extend to a complex system of reservoirs.

Computer simulation models are widely used for planning multiple reservoir water supply systems. These models are used to investigate different options such as water supply augmentation and to establish long-term operational strategies. The driving force for these simulation models is the operating rules. As water resources become more fully utilized, it is necessary to operate the systems efficiently by using optimal operating rules. These operating rules may also be used as input to the simulation models describing the systems. A generic methodology is developed, using stochastic dynamic programming (SDP), to determine the operating rules in terms of reservoir targets for urban water supply reservoir systems. The SDP explicitly accounts for the stochastic nature of streamflow to the water supply system by considering a theoretical probability distribution for streamflow, which is a major advantage of the method. Moreover, the method theoretically produces the global optimal solution. The methodology is applied to the Melbourne urban water supply system in Australia to produce the reservoir targets. The conclusion made is that the SDP provides an objective method of deriving the reservoir targets for urban water supply reservoir systems, thereby providing satisfactory and acceptable operating rules.

A low-cost urban storm-water sampling device (culvert composite sampler) has been designed, developed, and field tested. The device provides an economical alternative to current procedures used for collecting flow-weighted composite samples required for NPDES monitoring, assessing urban storm-water inputs, and evaluating the effectiveness of best management practices. The composite sample volume collected during a runoff event is used to estimate the total runoff volume transported by a culvert during the storm. The sample is easily transferred to a laboratory bottle for chemical analysis that, with the total culvert flow estimate, is used to determine the pollution loading contributed by a drainage area to a receiving water body. The device costs less than $100, has no moving parts, and uses gravity flow. Initial studies of the proof of concept compared the performance of the culvert composite sampler against that of a flowsplitter composite sampler and manual sampling during three storm events at an established monitoring site. Tests were also performed in the controlled conditions in a laboratory hydraulic flume. The chemical results indicated that the culvert composite sampler closely approximated the flow-weighted composite collected with the flowsplitter (a true flow-weighted sampler). The culvert composite sampler estimated total culvert flow within 12% of the flow calculation based on manual sampling field measurements. Additional tests are in progress to observe the performance of the culvert composite sampler in a greater number and variety of storms events.

This paper describes the application of deterministic optimization to the main stem Missouri River reservoir system and the development and testing of inferred optimal operating rules from these model results. An implicit stochastic optimization approach is taken and tested using a simplified simulation model. This work illustrates the applicability and limitations of applying deterministic optimization to development of strategic operating rules for large-scale water resource systems. For this multipurpose multireservoir system, simple data display and simulation modeling are found to be superior to classical regression techniques for inferring and refining promising operating rules from deterministic optimization results.

Large-scale water problems require management actions by many players, but without coordinated frameworks for action, there will be gridlock, high legal expenses, and conflict-filled decision processes. However, implementing and sustaining coordinated frameworks is extremely difficult. The paper reviews five case studies to identify useful attributes of management frameworks based on inclusivity, process, and control and authority. Neither the management frameworks nor their attributes guarantee success against negative incentives of water industry players, and success also requires water service providers and regulators to take on, in addition to their principal roles, extended water citizenship roles to help solve large-scale problems.

Many powerful optimal design models have been developed for municipal water-distribution networks, but few are in practical use since they are difficult for water engineers to understand and require an extensive data base for implementation. To aid in technology transfer of water-distribution system optimizers, a prototype decision support system WADSOP (Water Distribution System Optimization Program) is presented to guide water-distribution system design and analysis in response to changing water demands, timing, and use patterns; and accommodation of new developments. WADSOP integrates a geographic information system (GIS) for spatial database management and analysis with optimization theory to provide a computer-aided decision support tool for water engineers. Several comparative studies show improved performance over published results. A real-world case study for the city of Greeley, Colo., water-distribution network is also presented.