Journal of Water Resources Planning and Management

Five alternative management plans were applied at two recharge dams in central Saudi Arabia with the aim of improving their recharge efficiencies. The management plans included the present management system, release of reservoir water to the downstream channel, release to a downstream basin, removal of silt from the reservoir bed, and scratching of the reservoir bed. The results of field applications were not easily comparable due to the topographical changes of the reservoir bed and the different sizes and times of floods throughout the seasons. A rational comparison of recharge efficiencies are made through simulations. Field experiments showed that alternatives concerning silt removal from and scratching of the reservoir bed produce substantial improvements in recharge efficiency.

An ARIMA (auto regressive‐integrated‐moving‐average) time‐series modeling framework is used to assess the effectiveness of water‐conservation measures taken in the Greater Athens Area of Greece after May 1990, in an effort to cope with a pending water shortage. The models used include two components; the first forecasts historical water consumption and the second accounts for the potential effects of conservation. Total and residential charged water consumption are examined and a statistically significant drop in their levels is revealed. In the absence of other important events that could have influenced water consumption, it is concluded that the observed decline with respect to the forecasted value of water consumption can be safely attributed to the conservation measures taken. Although a dramatic increase in the price of water was the most important component of the conservation effort, the present study cannot be used as the sole basis for gauging its particular contribution. Additional analyses toward this objective are recommended in the conclusions.

An integrated approach combining deterministic dynamic programming and simulation models has been developed and applied to determine the optimal operation policy and performance of a mixed hydro‐thermal power system consisting of a reservoir, and several run‐of‐the‐river hydroelectric and thermal power plants. The objective of the optimization model is to maximize annual firm energy generation while treating the outputs of the run‐of‐the‐river and thermal power plants as parameters. Simulation of the combined system is based on a standard operating rule, imposing an additional constraint of target demand derived from the dynamic programming model. Stochastic behavior of the system is considered implicitly by introducing synthetic flows. Comparison of combined and separate operations of the reservoir with the run‐of‐the‐river and thermal power plants shows that combined operation is advantageous. For the investigated system in Nepal, combined operation improves the output by 26%. The target demand of 1,226.7 GWh is satisfied with a mean overall reliabilitiy of 98.8%, a dry season reliability of 97.2%, maximum deficit of 5.6%, and average maximum number of consecutive failure months of 4.2.

Design floods of specified frequency are used to consider relevant hydrologic and economic factors in the evaluation of operation, or changes in operation, of flood‐damage mitigation facilities. The design flood hydrograph is constructed using flood volumes, often extrapolated beyond observed records, from flood‐volume‐duration‐frequency curves. We examined the foundation of this approach using flood flow data from seven Pacific Northwest river catchments. Nested occurrence of large‐return‐period flood volumes (i.e., 1‐day and n‐day flood volumes occur concurrently), for flood durations important to decision making, held true for all seven basins. Coincidence of floods occurs when the 1‐day and n‐day flood volumes have the same return period. Flood volume‐frequency, and duration for the largest two or three flood volumes is strongly related (coincident) in three catchments and moderately related in three others. No apparent relationship was observed in the seventh. No link is apparent for any of the seven catchments between catchment physical and climatological features and flood‐volume concurrence or coincidence of frequency. These results indicate the flood‐hydrograph‐frequency record for each catchment should be evaluated prior to using assumed nested volume relationships to derive a design flood hydrograph having a given exceedance frequency. A general method for constructing design flood hydrographs for low exceedance probabilities (high return periods) is given.

Traditional principles for the design, operation, and evaluation of irrigation systems do not adequately incorporate the scarcity value of water. This paper presents an operational framework that attempts to integrate economic concepts into irrigation design and management. By means of a simple spatial optimization model, conditions are derived for optimal water allocation at each location in the system. Principles for optimal investment in distribution canals and in water conservation technology on the farm are obtained. Irrigated area and aggregate water use are determined. The potential economic benefit of the proposed model is demonstrated through an illustrative example.

Three models were developed and tested for the optimal capacity expansion planning in a hypothetical multiaquifer system. The response of the system was included in the models using response matrices. All models are 0/1 mixed‐integer programming models and enable the determination of minimum capital investment and operation costs of well fields and associated pipeline facilities while satisfying a set of system constraints. The performances of the models are compared in terms of computational requirements and approximation to pumpage costs under three water‐demand schedules. Multiobjective analyses were conducted to develop trade‐off curves relating pumpage to drawdown. The sensitivity of the capacity expansion policies to variations in demand requirements, interest rates, and system parameters are analyzed. The first model produces minimum total drawdowns and requires lesser computation time while the remaining two models yield minimum total costs but require more computation time. The variations in demand requirements, interest rates and system parameters causes variations in selection of the potential well fields, their completion time, resulting total costs and minimum total drawdowns.

Currently used methods for long‐range water‐supply forecasting are compared with statistical time‐series tools, such as seasonal auto‐regressive integrated moving‐average modeling. Evaluation of several theoretical models under a range of flow conditions provided insight into development of a technique using engineering knowledge and experience to improve the quality of forecasts. Rules governing model selection are developed from analysis of forecast residuals within a sensitivity analysis. Context‐sensitive model selection provided a means of improving forecast accuracy. Increased confidence in the optimal forecasted operating and planning policies are consequences of improved forecasts. The modeling tools provide the means of evaluating the performance of long‐range monthly probabilistic stream‐flow forecasts at Manitoba Hydro. Manitoba Hydro is a large utility that operates a multireservoir electric‐power generation system. The needs and priorities of the system demand forecasts up to 1 year in advance for planning budgets and release policies.

Until recently most emphasis on implementing Maximum Contaminant Levels (MCLs) under the Safe Drinking Water Act and its Amendments (SDWAA) has been focused on drinking water as it leaves the treatment plant. However, the SDWAA has been interpreted as requiring that its MCLs must be met at the consumer's tap. This interpretation has forced consideration of the drinking‐water distribution system when measuring and monitoring contaminants for SDWAA compliance. It is increasingly apparent that water quality can undergo significant deterioration between the treatment plant and the consumer's tap. A field study conducted in conjunction with the South Central Connecticut Regional Water Authority using a contaminant propagation model demonstrated long residence times in one of its service areas, which suggested potential difficulties in maintaining chlorine residuals throughout the system. A follow‐up study verified that maintaining residuals is difficult and demonstrated that a simple first‐order decay model associated with modeling chlorine residuals is inadequate.

An adaptive smoothing‐filtering approach for on‐line forecasting of hourly municipal water use time series is presented. This method is suitable for forecasting an hourly water‐consumption time series that is influenced by changing weather conditions and measurement outliers. The proposed seasonal time‐series model and adaptive forecasting algorithm can capture both weekday and weekend cycles and produce very accurate forecasts from 1 h to 24 h ahead. The methodology is based on Winters' exponential smoothing, recursive least squares (RLS), and the Kalman filter. The Winters algorithm is useful for recursive updating and extracting time‐varying seasonal factors. The deseasonalized residuals are passed on to the RLS and the filter to correct model errors and to whiten the innovations. The on‐line adaptive forecasting system also utilizes a data preprocessing procedure to handle measurement outliers, which are caused by data‐recording errors and unmodeled disturbances. The validation tests conducted in the present study show that the forecasting system can maintain surprisingly small prediction errors, despite various unmodeled time‐varying climatic variabilities.

Engineering planning and design of a local flood warning system should include a reliability analysis. The reliability of warnings can be quantified in terms of the relative operating characteristic—a relation between the probability of detection and the probability of false warning for a zone of the floodplain—and its transformation, the performance trade‐off characteristic—a relation between the expected number of detections and the expected number of false warnings per year for a zone. Numerical procedures are derived for computing these two characteristics. Two case studies in Pennsylvania are reported. The case of Milton, a town on the West Branch of the Susquehanna River, demonstrates fundamental trade‐offs between the reliability and the lead time of warnings. The case of Connellsville, on the Youghiogheny River, demonstrates synergistic gains in warning reliability due to a coupled solution: a flood‐control dam of the U.S. Army Corps of Engineers and the river forecasting technology of the National Weather Service.

Mathematical models based on nonlinear programming are developed for operating recharge‐basin systems (also referred to as soil‐aquifer treatment systems). The objective of these optimization models is to determine the operation policy (loading schedules) that maximizes the infiltration volume subject to constraints for continuity, infiltration, ground‐water flow, and the physical constraints describing the recharge basins. Two basic physical processes that are involved in the recharge‐basin systems are the infiltration process and the soil‐moisture‐redistribution process. The infiltration process is modeled using both the Philip's and the Green‐Ampt infiltration models, and the soil‐moisture redistribution process is modeled using Darcy's equation as well as a kinematic‐wave model. An improvement on the developed models is to consider the final moisture content at the end of each cycle time as a decision variable; which also allows the total cycle time to become a decision variable. In the modified applications, the objective is changed to maximizing the infiltration rate instead of maximizing the infiltration volume. Several hypothetical applications are presented to illustrate the modeling procedure.

This paper examines strategies for forming public‐private sector partnerships in order to improve the distribution of water in rural areas in Ghana. The options explored include: (1) An outright sale of the existing government‐controlled water corporation; (2) setting up decentralized regional water utilities; (3) maintaining the existing central authority but contracting out services to the private sector; (4) charging user fees for water services based on the cost of producing and distributing the water; and (5) encouraging private and community‐level institutions to participate in the water market. Based on a limited case study, the paper finds a wide disparity between public and private prices of water, which points to a need for more‐rigorous pilot programs and studies to further explore alternatives for public‐private partnerships in the Ghana water sector.

A management model is developed that uses a nonlinear programming approach to solve the optimal control problem of managing the generation and disposal of agricultural and dairy waste. The permissible controls are subject to physical, economic, and social constraints. The model uses a state response matrix to represent the response of the physical state of the system, and a policy response matrix that reflects the effect of policy actions such as pumping, recharge, and manure disposal on the state of the system. Unlike some combined simulation/optimization approaches, this model includes the dynamic response of the system as an explicit part of the optimization. To evaluate the applicability of the model to actual policy problems, the model is implemented in the Chino ground‐water basin, California. Based on the alternative scenarios analyzed, a manure‐treatment and ‐disposal program coupled with an artificial‐recharge program are proposed. The rate and schedule of treatment, disposal, and recharge are determined on the basis of the transport capacity of the underlying aquifer and associated costs. The model may be used for analysis of ground‐water quality regulations or other management options on the physical state and economic parameters of the system.

Planning of water resources for municipalities requires the same engineering and management principles no matter at which government level it is conducted; however, there are some advantages to primary involvement at the local level. Local concern for environmental management has engaged citizens from nine municipalities in Bucks County, Pennsylvania to cooperate on ground-water resources planning and exploring the best approach to meet the needs of the area; and forming a committee that acts as a means for involving citizens and environmental groups, essential to the success of any water resources planning. The committee deliberates on ground-water issues such as planning ordinances, water conservation, protection of important recharge areas, drought management, and maximum ground-water withdrawal rates, which will be supported by the hydrologic system. As a consortium, the municipalities also initiated a hydrogeologic study. An additional impetus is the Pennsylvania Municipal Planning Code, which allows municipalities to manage ground-water resources to ensure their availability and quality.