摘要:

A mathematical model for optimal real‐time operation of a regional water system was developed and examined. The regional system consists of numerous water sources with various water qualities and a variety of consumers with different flow and quality requirements. In order to satisfy the different consumer constraints, nodal flow and solute balances were defined. Pump and valve‐on and valve‐off situations were defined by continuous nonlinear equations. The model was solved numerically for a short time period by a projected Lagrangian method for the water supply system in the Arava Rift Valley, Israel. The global uniqueness of optimal solution was

ISSN:0043-1397    

DOI:10.1029/91WR02693

年代:1992

数据来源: WILEY

摘要:

This paper analyzes the optimization of water storage of small‐scale dams (tanks) found in the semiarid regions of Asia. The focus is on monsoonal water storage in small tank systems in Sri Lanka, and in particular on optimal extraction for supplementary irrigation under double cropping, also allowing for nonirrigation uses of storage. The problem of intraseasonal allocation of storage for irrigation is solved by deterministic dynamic programming (DP) using simulated crop response functions. An approach to solving the optimal interseasonal allocation problem is demonstrated by operating in sequence the DP models for the two seasons. An important feature is the generation and use of seasonal water response functions with respect to each cropping season ensuring optimality in both crop area and intraseasonal distribution of irrigation. The determination of the scarcity value of water in this framework is also illustrated. Our results show that in most years both the optimal conservation of storage from the wet season and the optimal area of irrigation in the dry season are much higher than the current practic

ISSN:0043-1397    

DOI:10.1029/92WR00199

年代:1992

数据来源: WILEY

摘要:

Operation of reservoir systems using stochastic dynamic programming (SDP) and Bayesian decision theory (BDT) is investigated in this study. The proposed model, called Bayesian stochastic dynamic programming (BSDP), which includes inflow, storage, and forecast as state variables, describes streamflows with a discrete lag 1 Markov process, and uses BDT to incorporate new information by updating the prior probabilities to posterior probabilities, is used to generate optimal reservoir operating rules. This continuous updating can significantly reduce the effects of natural and forecast uncertainties in the model. In order to test the value of the BSDP model for generating optimal operating rules, real‐time reservoir operation simulation models are constructed using 95 years of monthly historical inflows of the Gunpowder River to Loch Raven reservoir in Maryland. The rules generated by the BSDP model are applied in an operation simulation model and their performance is compared with an alternative stochastic dynamic programming (ASDP) model and a classical stochastic dynamic programming (SDP) model. BSDP differs from the other two models in the selection of state variables and the way the transition probabilities are formed and update

ISSN:0043-1397    

DOI:10.1029/92WR00103

年代:1992

数据来源: WILEY

摘要:

A stochastic optimization model for containment of a plume of groundwater contamination through the installation and operation of pumping wells is developed. It considers explicitly uncertainty about hydraulic conductivity in the aquifer and seeks to minimize the expected total cost of operating the pumping wells plus the recourse cost incurred when containment of the contaminant plume is not achieved. Four different formulations of the model are examined, ranging from simply replacing all uncertain parameters by their expected values to a full stochastic programming with recourse model involving nonsymmetric linear quadratic penalty functions. The full stochastic programming with recourse model, which minimizes the expected total costs over a number of realizations of outcomes of the random parameters, is nonlinear and possibly nonconvex and is solved by an extension of the finite generation algorithm. The value of information about the uncertain parameters is defined through the differences between the values of the optimal solutions to the different formulations. A sample problem is solved using all four formulations. The results indicate that the explicit incorporation of uncertainty does make a difference in the solutions obtained. The work indicates that stochastic programming with recourse is a useful tool in management under uncertainty, and that it can be used with reasonable computational resources for problems of moderate size.

ISSN:0043-1397    

DOI:10.1029/92WR00038

年代:1992

数据来源: WILEY

摘要:

A multidimensional stochastic model is developed for the space‐time distribution of daily precipitation. The rainfall is linked to the atmospheric circulation patterns using conditional distributions and conditional spatial covariance functions. The model is a transformed conditional multivariate autoregressive AR(I) model, with parameters depending on the atmospheric circulation pattern. The model reproduces both the local rainfall occurrence probabilities and the distribution of the rainfall amounts at given locations, and the spatial dependence described with the help of cross‐covariances of the transformed series. Parameter estimation methods based on the moments of the observed data are developed. A simulation procedure for the model is also presented. Its link to atmospheric circulation patterns makes it suitable for local precipitation simulation under stationary and nonstationary arrivals of atmospheric circulation patterns such as climate change. The model is applied using the classification scheme of the German Weather Service which is available for the time period 1881–1990. Precipitation data measured at 44 different stations for the time period 1977–1990 in the catchment of the river Ruhr (Germany) are used to demonstrate th

ISSN:0043-1397    

DOI:10.1029/91WR02589

年代:1992

数据来源: WILEY

摘要:

Pressure transients associated with a constant‐rate pumping test in a double‐porosity (fissured or multilayered) reservoir may exhibit, in succession, several periods of characteristic log linear dependence on time. If the flow in the matrix blocks is primarily vertical then slope halving of the semilog gradient may be observed, but if the radial component of block flow becomes significant then pressure stabilization can occur. During the final period of formation flow an increase in gradient is associated with a dominant vertical component of block flow, but if the radial component is significant then a decrease in gradient will be obser

ISSN:0043-1397    

DOI:10.1029/91WR01234

年代:1992

数据来源: WILEY

摘要:

A method for coupling sorption kinetics and solute advection in particle‐tracking models is proposed; this method is efficient for the case where sorption rate coefficients can be assumed constant field scale parameters. A simulation example of reactive solute advection in two‐dimensional heterogeneous porous media is presented. The effect of sorption kinetics on solute advection is investigated. Nonequilibrium effects are exhibited as enhanced tailing in the solute breakthrough. Because high variability in the hydraulic conductivity also yields enhanced tailing, the nonequilibrium effect is more pronounced for the case of low variability. Moreover, it may be difficult to distinguish cases of low variability with nonequilibrium sorption from cases of high variability with equilibrium sorption. A comparison of Monte Carlo ensemble results is made with an analytical model for the mass arrival of kinetically sorbing solute in heterogeneous porous media obtained using first‐order perturbation. The comparison indicates that the analytical model provides reasonable approximations of the expected solute breakthrough if the variance of the natural logarithm of the hydraulic conductivity is smaller t

ISSN:0043-1397    

DOI:10.1029/92WR00011

年代:1992

数据来源: WILEY

摘要:

Microscale Eulerian variations in the flux, mineralogical composition and size of suspended particles have been found in a contaminated sandy aquifer under natural gradient flow conditions () during an 8‐month study period. Particle variability has been detected along a 16‐m saturated section of the aquifer at a scale of centimeters and meters in the vertical and horizontal dimensions, respectively. The average concentration of particles in groundwater varied between 1 and 40 mg/L, but high concentrations of up to 5000 mg/L were determined in specific 3‐cm vertical intervals of the aquifer. The particles were primarily composed of CaCO3(11–57%), quartz (7–39%) and clays (8–43%). Most of the particles were within the 140–3000 nm size range with size modes varying from 310 to 660 nm. The large amounts of suspended particles are considered to be related to high inputs of dissolved organic carbon into groundwater, from sewage effluents which have been used for agricultural irrigation since the early 1960s. As a result of organic matter biodegradation in the saturated zone, anoxic conditions developed and thepCO2content of groundwater increased dramatically (pCaCO2= 10−1.8to 10−1.3atm). It is postulated that part of the carbonate cement of the rocks dissolved and detrital CaCO3, quartz and clay were released as colloidal particles. Part of the clay particles could have also been transported through the unsaturated zone into groundwater after mobilization from surface layers as a result of the intermittent input of water of different chemical quality. In the prevailing anoxic conditions of groundwater at the study site (dissolved oxygen concentrations of<1 mg/L) colloidal stability is enhanced by organic matter coa

ISSN:0043-1397    

DOI:10.1029/91WR02978

年代:1992

数据来源: WILEY

摘要:

Based on existing principles of automated drainage network extraction we have developed two methodological algorithms, the “profile scan” and “hydrological flow modeling,” and used them to extract networks from digital elevation models (DEMs). The “hydrological flow modeling” algorithm specializes in the extraction of well‐connected hierarchically arranged skeletal channel networks. On the other hand, the channels extracted by the “profile scan” algorithm lack adequate connectivity, but this algorithm is suitable for the extraction of wide valley bottoms and other flat areas. A combination of the two algorithms gives a more versatile algorithm capable of yielding networks which are not only well connected but also portray the surface character of the drainage network thus generated. The good functioning of our algorithm is not inhibited by the presence of pits in the DEM. There is therefore no preprocessing of the DEM prior to drainage extraction. Rather, at the end of extraction, isolated spots are eliminated since these are the ones most probably repre

ISSN:0043-1397    

DOI:10.1029/91WR03098

年代:1992

数据来源: WILEY

摘要:

Vertical heterogeneity is incorporated in a stochastic transport model, in which the soil is viewed as consisting of an ensemble of essentially vertical, independent stream tubes. The saturated hydraulic conductivity in each stream tube is defined as the vertical average of the corresponding point random process. The statistics of the vertically averaged hydraulic conductivity and the resulting statistics of solute travel time are depth dependent. The evolution of the field scale breakthrough curve with depth is analyzed in terms of the first two moments of solute travel time to an arbitrary depth below the soil surface. The arrival time of the solute center of mass, quantified by the expected travel time, grows linearly with depth also for vertically heterogeneous soil. The temporal solute spreading around its center, quantified by the travel time variance, may exhibit a compression‐expansion that is qualitatively analogous to the solute plume behavior in the studies of Butters and Jury (1989), Russo (1991), and Ellsworth and Jury (1991). The relative solute spreading, quantified by the travel time coefficient of variation, decreases with increasing dept

ISSN:0043-1397    

DOI:10.1029/92WR00166

年代:1992

数据来源: WILEY