Journal of Water Resources Planning and Management

Three ground‐water management models were developed to determine the optimal planning and operating policies of a multiaquifer system in eastern Saudi Arabia for an eight‐year planning period. The modeled system, which consisted of the Alat, Khobar, and Umm Er Radhuma aquifers, was represented by a three‐dimensional simulation model included in linear and quadratic optimization models using response functions. Yearly optimal pumping policies were determined for 52 well fields under three management objectives that maximized agricultural water withdrawals and minimized total drawdowns, and pumping costs subject to constraints related to the system's response equations, demand requirements, drawdown limitations, and discharge bounds. Multiobjective analyses were conducted to develop trade‐off curves relating increased agricultural water production to drawdown, aquifer dewatering, and pumping costs. Modeling results show the agricultural water production could be increased by almost two and a half times without causing dewatering. Optimal pumping schedules differed, depending upon the type of objective function employed. The best option appears to be the one in which extensive water transport is allowed between municipal well fields.

The paper concerns the problem of minimization or leakage in water‐distributed networks. It has been reported that leakage from some networks may account for a significant amount of the water put into supply. For some aging urban networks, rates of up to 50% have been quoted, with average rates of 25% being quite typical. These high rates of leakage represent a significant economic loss. An algorithm for the determination of flow control valve settings to minimize leakage is presented. The nonlinear network equations describing nodal heads and pipe‐flows are augmented by terms that explicitly account for pressure‐dependent leakage and by terms that model the effect of valve actions. Successive linearization of these equations using the linear‐theory method allows a linear program that minimizes leakage to be formulated and solved. The performance of the method is demonstrated by application to an example network.

Debris basins are a common engineering structure used to control debris flows. Knowledge of the risk of failure as a function of important design variables can improve decision making and can be used as a basis for minimizing the total annual cost (i.e., construction and maintenance plus risk cost). The failure risk was computed for four policy elements: the rainfall frequency, the interval between significant watershed burn, construction and dredging accuracy, and the regularity of maintenance of the debris basin. The burn interval and the rainfall magnitude are the two most important variables associated with the failure risk, with the expected annual risk varying from less than 1% to as'much as 65% for different burn intervals and rainfall frequencies. A failure to maintain the basin can double the risk or failure. The risk of failure does not appear to change much for typical construction and dredging‐volume accuracy. The risk estimates were made using a model developed from data from the southern California area and the conditional expectation variance reduction technique.

Laws governing ground‐water withdrawals have been adjusted to reflect the desire and need to prevent resource depletion and conflict among users. Courts today are inclined to regard ground water more as a shared public resource that is subject to management and regulation than as private property with rights of unlimited use. Also, state legislatures are passing comprehensive ground‐water‐management statutes to prevent depletion and conflict and to reduce historic reliance on the courts to settle ground‐water disputes. This has been called a “management doctrine” for ground water. One example of the management doctrine is the use of ground‐water‐management areas to regulate regional ground‐water withdrawals when and where that is necessary. This paper summarizes the results of a nationwide survey to collect information about the nature and distribution of ground‐water‐management‐area programs around the country. Results show that 27 states allow for formation of special management areas to address some type of ground‐water‐quantity problem; some areas also address ground‐water‐quality problems. This paper describes some of the common aspects of management‐area programs. One distinction of interest is that while most states place the responsibility of controlling management areas with some central state agency, several states have opted to leave that responsibility with the local ground‐water users. The heavily irrigated states of Colorado, Kansas, Nebraska, and Texas stand out in this regard.

A ground‐water strategy is a policy document that outlines how a state can best manage its ground water, consistent with budgetary limitations and with provisions of federal and state law. This paper outlines such a strategy, as adopted in New Jersey, which establishes policies for water‐supply and water‐quality protection. The strategy includes two new directions critically important to successful ground‐water management. First, a state program is proposed to control nonpoint sources of ground‐water pollution. Second, the strategy corrects the lack of coordination among state programs that provide alternative water supplies to replace contaminated wells and among programs requiring cleanup of hazardous water pollution. Alternative water supplies that are constructed without regard to pollution mitigation may allow the party responsible for the pollution to escape liability for full remedial costs. Due to such circumstances, water‐supply remedies in severe cases may be delayed, even where sufficient public funds exist. The strategy solves this problem through a common priority system for both water‐supply and pollution‐mitigation remedies, and by addressing first those portions of cases that pose major public‐health risks and afterward, remaining portions of those cases.

Although available technology may be inadequate for the complete remediation of certain contaminated ground water‐sites, hydraulic control can be used to reduce the extent of, and contain, ground‐water contaminants until adequate technology can be developed. The design of such a remediation system can be viewed as a two‐stage process. A first stage is the achievement of a reduction of the extent of the contaminant, and a second stage is the maintenance of the contaminant at this reduced areal extent. Viewed in this light, alternative pump staging criteria can be considered within the design process. These criteria can include allowing the well location and pumping rate to change during the remediation effort. This paper analyzes the economic significance of incorporating increasing complexity of pump‐stage criteria into the design process. The analysis is conducted using numerical simulation and a new multistage optimization formulation. The analysis concludes that while different pumping strategies should be used in each stage of remediation, it is generally unnecessary to consider the impact of the pumping strategy in the first stage on the remediation cost in the second stage.

A regional hydrologic model is developed for estimating flow‐duration curves at ungauged and unregulated basins in Massachusetts. Flow‐duration curves often exhibit complex shapes, requiring probability density functions with three or more parameters. This study approximates the lower half of daily flow‐duration curves using a two‐parameter lognormal probability density function. A conjugate gradient algorithm is employed to fit lognormal density functions to the lower half of observed flow‐duration curves at 23 basins. Regional regression equations are developed to describe the lognormal model parameters in terms of easily measured basin characteristics. The resulting regional flow‐duration model only requires estimates of the watershed area, and a basin relief parameter, both of which are easily obtained from U.S. Geological Survey 7.5‐min quadrangle maps. In addition, confidence intervals are derived for flow‐duration curves estimated at ungauged sites. A validation experiment reveals that the resulting regional hydro‐logic model can provide remarkably precise estimates of a flow‐duration curve at an ungauged site, considering the simplicity of the model and its ease of application.

A review of studies on reallocation of reservoir storage capacity for reservoirs in the Corps of Engineers and state of Texas has identified eight general cases of reallocation: (1) Use of water‐supply storage not under contract; (2) temporary use of storage allocated for future conservation purposes and sediment; (3) storage made available by change in conservation demand or purpose; (4) seasonal use of flood‐control space during dry seasons; (5) reallocation of flood‐control space; (6) modification of reservoir‐water‐control plan and method of regulation; (7) raising existing dams; and (8) system regulation of corps and noncorps reservoirs. While these general cases suggest a variety of opportunities for reallocation, feasibility must be evaluated for each specific site. A memorandum of understanding between the state of Kansas and the Department of the Army illustrates the different hydrologic, economic, environmental, legal, and institutional considerations required in reallocation investigations and the value and necessity of cooperation between responsible and interested parties.

This paper presents a methodology that can be used for determining the optimal freshwater inflows into bays and estuaries for the purpose of balancing freshwater demands with the harvest of various types of estuarine resources (e.g., finfish and shrimp). The optimization problem is a nonlinear programming problem solved using a generalized reduced gradient technique. Salinity is expressed as a function of freshwater inflow in a nonlinear regression equation and used as a constraint. Additional nonlinear constraints are the harvest regression equations for the various species that express harvest as a function of the quantity of freshwater inflow. Because of the uncertainty associated with the regression equations for salinity and harvest, these constraints are expressed in a chance‐constrained formulation. The methodology is applied to the Lavaca‐Tres Palacios Estuary in Texas. The results of the numerical application indicate that the minimum freshwater inflow requirement increases as the required reliability of chance constraints increases. The uncertainty in the regression equations limits the maximum achievable reliability.

A procedure is presented for design of detention basins for industrial sites. The procedure involves simulating the operation of the detention basin for the entire period of rainfall record in order to determine the storm runoff storage requirements as a function of recurrence interval, the treatment duration relationship, and the storage volume duration relationship for different maximum rates of treatment of outflow. These results can then be used to consider the trade-offs between storage volume, treatment rate, storage duration, treatment duration, and frequency of the design event being equalled or exceeded.