摘要:

The problem of meeting stream dissolved oxygen standards while optimizing some objective is treated. New properties of the oxygen sag equation allow the constraint set of such mathematical programs to be described to a high degree of accuracy by linear inequalities; except for upper and lower bounds on pollutant discharges, three linear constraints at most are required per reach. Constraint elimination techniques are developed that can further reduce the number of constraints necessary. As a means of highlighting the potential power of these techniques to large‐scale models they are applied to two well‐known examples from the literat

ISSN:0043-1397    

DOI:10.1029/WR011i002p00191

年代:1975

数据来源: WILEY

摘要:

A linear decision rule (LDR) in reservoir management and design is reviewed and transformed. A generalized formulation of a new LDR is presented, and the necessary steps to implement it are carried out for a particular form of the new rule. The proposed rule permits further minimization of expected losses arising from deviations of releases from prespecified target levels. The use of the rule also makes possible a larger minimum commitment of water. The problem is solved for historical data from the Gunpowder River in Maryland under both the previous and the new form of the LDR. Results obtained are compared for the two cases.

ISSN:0043-1397    

DOI:10.1029/WR011i002p00197

年代:1975

数据来源: WILEY

摘要:

An algorithm is derived that determines the capacity and decision constants for a reservoir to be operated by use of the linear decision rule (LDR). The new algorithm supplants an earlier technique, which was fitted to a specialized problem format. The new algorithm will serve for any feasible formulation of a reservoir operating by the linear rule and may easily be implemented without the computer.

ISSN:0043-1397    

DOI:10.1029/WR011i002p00204

年代:1975

数据来源: WILEY

摘要:

Three criteria are established for the evaluation of the utility of multiobjective programing techniques for water resource planning. The criteria are computational efficiency, explicitness of trade offs among objectives, and the amount of information generated for decision making. The multiobjective approaches are classified into generating techniques, techniques which rely on the prior articulation of preferences, and techniques which foster iterative definition of preferences. The methods in the various classes are reviewed and evaluated in terms of the hypothesized criteria. The evaluations are then used in establishing conclusions about the applicability of the multiobjective approaches to water resource problems.

ISSN:0043-1397    

DOI:10.1029/WR011i002p00208

年代:1975

数据来源: WILEY

摘要:

A stochastic analysis is performed on the extreme drought duration defined to be the maximum dry interval for a point rainfall process. The assumptions underlying previous analyses are generalized to those of a nonhomogeneous Poisson process. Analytical results, which seem intractable in general, are derived for two particular forms of the intensity function of the Poisson process; for a general intensity function, simulation is recommended. Next, small time intervals such as the growing season of a crop are considered so that the assumption of a homogeneous Poisson rainfall process may be made and the effect of parameter estimation on the theoretical results may be studied qualitatively. To illustrate this point, four estimates of the intensity parameter are calculated by using precipitation data from Chicago and Austin. A good agreement is found between the theoretical and empirical distribution functions for the two parameter estimates calculated by use of the model developed in this investigation; on the other hand, a substantial bias is present for parameters calculated directly from the data. Finally, an approach is schematically indicated to extend the model to regional droughts by using stochastic superposition.

ISSN:0043-1397    

DOI:10.1029/WR011i002p00221

年代:1975

数据来源: WILEY

摘要:

Mathematical properties of the three‐parameter log normal probability distribution are detailed. Two methods for estimation of the third parameteraare compared. The estimator ofausing sample mean, median, and standard deviation is found to be more variable and have larger bias for distributions of interest in operational hydrology than the estimator using sample mean, standard deviation, and skew. Graphical solutions for the third parameteraare presented; a single feasible value ofais shown to result when the skew estimator is used; two feasible solutions result when the median estimator is used. The smaller of the two solutions is shown to correspond to skews of less than 5.87 and hence is the desired solution in most hydrologic application

ISSN:0043-1397    

DOI:10.1029/WR011i002p00229

年代:1975

数据来源: WILEY

摘要:

The class of nonnegative, initially relaxed, and nonanticipating systems has many applications in engineering. In this paper a proof is given to a theorem stating that in this class of systems, if the input total mass is equal to the output total mass, then for any nonnegative input‐output pair, the system fulfills also a partial mass condition. In applying this theorem to systems expressed by the Volterra series it is concluded that the input functions must be bounded. Two such bounds on the input functions are considered: (1) bounds resulting from the requirement of a nonnegative output and (2) bounds resulting from the mass‐conserving property of the system. The theorem mentioned above implies that the set of input functions causing nonnegative output functions is a subset of the set of input functions that do not violate the mass‐conserving property of the system. It is therefore clear that the bounds of type 1 are the dominant among the two bounds for any nonnegative input function. In a system expressed by anNth order Volterra series the bounds on the input can be evaluated by solving a polynomial inequality of orderN‐ 1. An example is given for a system expressed by a third‐order Volterra series in which the bounds on the input form two regions. Explicit equations for the bounds of type 1 and 2 are derived for a second‐o

ISSN:0043-1397    

DOI:10.1029/WR011i002p00236

年代:1975

数据来源: WILEY

摘要:

Herein a simple numerical model for both overland and channel water routing is presented. A second‐order nonlinear scheme is developed to solve the kinematic wave equation with the boundary condition of time variant inflows. The numerical solutions agree very well with analytical solutions which are available for some particular cases. This model includes the effects of rainfall on flow resistance and simulates hydrographs which agree very well with experimental results for both constant rainfall and variable rainfall cases. The interesting phenomena of ‘pip’ and ‘dip’ in overland flow hydrographs are successfully simulated. These phenomena are found to be the results of sudden changes of flow resistance due to ceasing or starting of rainfall. The same routing procedure for overland flow is employed to route flow in natural

ISSN:0043-1397    

DOI:10.1029/WR011i002p00245

年代:1975

数据来源: WILEY

摘要:

A finite difference model of the behavior of an aquifer without stream interaction was developed as a first‐stage component of a management model of a stream‐aquifer system. The model is not built as a usual simulator but as a discrete impulse response generator. Once the basic response coefficients have been generated, the finite difference model is no longer necessary to simulate the behavior of the aquifer. Any aquifer response (e.g., return flow to a given reach for a given week) is expressed as an explicit function of the pumping rates. A complete description of the ‘discrete kernel generator’ is provided including the basic equations, truncation error propagation, accuracy, and ru

ISSN:0043-1397    

DOI:10.1029/WR011i002p00253

年代:1975

数据来源: WILEY

摘要:

A natural snowpack with ice layers is described in terms of an equivalent anisotropic porous medium. The anisotropic permeability is represented as a diagonalized matrix whose principal values can be calculated from a small amount of information about the prototype snowpack. Ice layers increase the transit time for water movement by a factor equal to the ratio of the principal values of permeability. The flow path, volume flux, and wave speed are determined by the slope of the snowpack and principal values of permeability. When a snowpack is assumed to be isotropic, the error in calculating transit time increases with the difference between the principal values of permeability. Usual variations in slope introduce a small change in the transit time.

ISSN:0043-1397    

DOI:10.1029/WR011i002p00261

年代:1975

数据来源: WILEY