摘要:

The effects of acidic atmospheric inputs on forest nutrient status must be assessed within the context of natural, internal acid production by carbonic and organic acids as well as the nutrient inputs and drains by management practices such as harvesting, fire, and fertilization. In all cases the anion associated with acid inputs must be mobile in the soil if leaching is to occur; immobilization of anions can effectively prevent cation leaching. Soil acidification will occur only if the often substantial buffering capacity of the soil in question is exceeded by acid inputs and if cation weathering from primary minerals is insufficient to offset cation losses by leaching. Such circumstances are rare but certainly could occur in theory, at least, given sufficiently large acid inputs on poorly buffered soils. Soils most sensitive to change are thought to be those of moderately acidpH and low cation exchange capacity. Neither very acid soils nor neutral, highly buffered soils are sensitive to acidification by acid rain. Given extremely high acid inputs, acid rain can cause temporary increases in nitrogen mineralization and nitritication as well as Al mobilization in soils. While temporary increases in N availability can cause increased forest growth in N‐deficient forests, increased Al availability can cause toxic reactions in tree roots. Little is known about tree Al toxicity levels as yet, however. It must be emphasized that assessment of acid rain effects is a problem of quantification. Given sufficiently high inputs on sensitive sites, negative effects of acid rain must occur, as is true of inputs of any substance, including H2O. Acid rain inputs of sufficient magnitude to cause acute effects, such as growth increase due to N mobilization or growth decrease due to Al mobilization, are apparently very rare under ambient field conditions. Long‐term effects on forest nutrient status can be either beneficial or adverse, depending on site nutrient status, silvicultural practices, and amount of atmospheric inp

ISSN:0043-1397    

DOI:10.1029/WR018i003p00449

年代:1982

数据来源: WILEY

摘要:

A multiattribute utility function was used to specify the decision‐maker's preferences, along with a zero‐one budget model, to solve the problem of selecting among interrelated multiobjective long‐range projects. Increasing the number of projects increases the complexity of the problem. The advantages of the model for relatively small problems are demonstrated by a case study dealing with a subset of Israeli water development projects for 1981.Full article is available on microfiche. Order from American Geophysical Union. 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document W81‐002; $1.00. Payment must accompan

ISSN:0043-1397    

DOI:10.1029/WR018i003p00462

年代:1982

数据来源: WILEY

摘要:

Different methods for allocating the joint costs of water supply projects among users are compared on the basis of certain commonsense principles of equity. We contrast the separable costs‐remaining benefits (SCRB) method with simple proportional allocation schemes and more sophisticated methods from cooperative game theory, including the Shapley value and variants of the core. Advantages and disadvantages of the methods in practice are examined using a regional water supply system in Sweden. It is argued that these principles provide a useful framework for choosing intelligently among methods. The appropriateness of a method depends on the context, especially on the reliability of information about costs and demands. The conclusion is that there is no one best method, although from a normative standpoint the SCRB method may be one of the wors

ISSN:0043-1397    

DOI:10.1029/WR018i003p00463

年代:1982

数据来源: WILEY

摘要:

Numerous ad hoc methods are used to apportion the costs of a water resource project among participants and/or purposes. Unfortunately these procedures do not always work, i.e., they lead to unfair assignment of costs. Accepted criteria for efficiency/financial analysis used in the water resources field are expressed in axiomatic form. These criteria are compared to accepted axioms of fairness from cooperativen‐person game theory. Similarities between the two approaches are identified. The minimum costs, remaining savings (MCRS) method is proposed as an improved method of financial analysis. The MCRS method can be viewed as a generalization of the presently used separable costs, remaining benefits metho

ISSN:0043-1397    

DOI:10.1029/WR018i003p00476

年代:1982

数据来源: WILEY

摘要:

Solutions of stochastic‐conceptual flow problems obtained by utilizing a single stochastic parameter, the scaling factor α, are compared with solutions obtained by using multivariate parameter distribution. Two cases of one‐dimensional vertical flow are analyzed: (1) piston flow of solute under steady uniform surface water recharge and (2) transient water flow when uniform recharge rate is applied on the surface. Under steady vertical infiltration, expressing the variabilty of the hydraulic conductivity functionK(θ) by the single stochastic‐variate α gives essentially the same results as the case when the variability inK(θ) is expressed by three stochastic variates. The agreement between the simulated average solute concentration profiles obtained by the two methods is improved as the recharge rate increases and a larger portion of the field is under ponding conditions. Similar results are found for the simulated potential runoff. For the case of the transient flow of water the variability inK(θ), as well as the variability in the soil water retentivity functionh(θ), is expressed by a scaling factor α obtained from hydraulic conductivity data. Using α as the only stochastic variate resulted in mean water content (θ) profiles which are in a relatively good agreement with the mean θ profiles obtained when expressing the variability ofK(θ) andh(θ) by five stochastic variates. The agreement between the distributions of the θ profiles obtained by the two methods, is rather poor. This agreement, as well as the agreement between the distributions of the depth of the wetting fronts, calculated by the two methods, are only slightly improved by using α as water content dependent stochastic variate. The results suggest that the scaling factor α, as a single stochastic variate, can be successfully used for stochastic analysis of water and solute flows under steady and transient inf

ISSN:0043-1397    

DOI:10.1029/WR018i003p00483

年代:1982

数据来源: WILEY

摘要:

A general, physically based formulation of water and energy transport in partially saturated soil must account for the coupling between the fields of matric potential ψ and temperatureT. The formulation by de Vries (1958) is converted to one that employs ψ andTas the dependent variables. This conversion facilitates a significant generalization of the theory to accommodate the omnipresent complications of hysteresis and inhomogeneity. The limitations of the assumptions of local thermodynamic equilibrium are discussed. A finite element solution algorithm for the one‐dimensional equations is outlined and tested on a variety of problems. The computational results demonstrate the reliability of the numerical mo

ISSN:0043-1397    

DOI:10.1029/WR018i003p00489

年代:1982

数据来源: WILEY

摘要:

A management model is developed that determines the optimum economic recoverability of a particular hot‐water geothermal reservoir undergoing exploitation for electric power generation. The management model integrates a physical model of the reservoir that predicts the areas of pressure decline due to withdrawals, and pressure rise due to reinjection of spent fluid, with a model of a two‐stage steam turbine power plant that determines the quantity of electricity generated for a rate of hot‐water extraction. Capital costs, variable costs and annual fixed costs are obtained for the reservoir development, extraction and reinjection, the transmission system, and the power plant. Revenues are determined for electrical power production. Application of the management model to a simplified, yet realistic example reservoir demonstrates that the methodology developed in this report can be used for analyzing the management of an integrated geothermal reservoir power plant system. For the example reservoir, 12 potential sites are developed, five for extraction wells and seven for injection wells. The wells on these sites are used to develop up to 27 MW of electrical power over a 20‐year time i

ISSN:0043-1397    

DOI:10.1029/WR018i003p00499

年代:1982

数据来源: WILEY

摘要:

The use of nonlinear routing models within real‐time, adaptive, streamflow forecasting has been limited because of the linearity restrictions of the most popular filtering and optimal estimation techniques. This work proposes a linearization methodology suitable for nonlinear multidimensional functions of nearly Gaussian nonstationary processes. Lack of bias and exact preservation of moments are a few of the advantages of the procedure. In order to facilitate computations, simple analytical approximations for the linearization coefficients are offered. A state parameter covariance partitioning algorithm is proposed for real‐time estimation of the states and parameters of the linearized router. An illustrative example of its use, based on data from the Bird Creek basin in Oklahoma, is presen

ISSN:0043-1397    

DOI:10.1029/WR018i003p00513

年代:1982

数据来源: WILEY

摘要:

Between 6,800 and 21,000 1 of transformer oil containing polychlorinated biphenyls (Aroclor 1254) and chlorobenzenes were spilled when an underground pipe broke at a transformer manufacturing plant in Regina, Saskatchewan, Canada. Methods were developed to examine the surface and subsurface distribution of the contaminants. Contrary to initial expectations, large quantities of PCBs were found to have migrated both vertically and horizontally at the site. Polychlorinated biphenyls at concentrations of approximately 1000 mg/kg moved downward through granular fill and 9 m of fractured Regina clay. Contaminant migration along the interface of the clay and the upper unit of permeable granular fill probably accounts for the extensive lateral movement. It is argued that because of the low organic content of the geological units at the site (generally 0.9%) and the hydrophobicity of chlorinated organics like PCBs, contaminants at many locations exist in three phases: a dissolved aqueous phase, an adsorbed phase, and an oily liquid phase. Movement of the oily liquid seems to be the most likely explanation for the migration of large quantities of PCBs downward through fractures in the clay and laterally through the granular fill.

ISSN:0043-1397    

DOI:10.1029/WR018i003p00525

年代:1982

数据来源: WILEY

摘要:

The purpose of the second paper in this pair is to describe the hydrogeology and to account for the observed patterns of PCB contamination at the Federal Pioneer site in Regina, Canada. Six major hydrostratigraphic units were identified from detailed test drilling and sampling. From the surface downward these are a thin surface fill, the Regina clay, the Condie silt, the till zone, the interglacial silt, and the Regina aquifer system. This latter unit is an important source of potable groundwater. At present the nearest wells are hundreds of meters from the site. The permanent water table is situated below the Condie silt in sandy glacial till. An active perched groundwater system has developed within the thin fill layer beneath the floor of the plant. The extensive lateral flow of groundwater in this zone has contributed significantly to the spreading of PCBs at the site. The PCBs have also moved downward through fractures in the Regina clay and in the upper part of the Condie silt. It can be expected that capillary forces will halt the downward movement of Inerteen 70‐30® as fractures narrow or stop. However, the possible existence of fractures connecting the contaminated zone to the Regina aquifer system or the potential for transport as a dissolved phase in the groundwaters may permit PCBs migrate downward to the aquifer or to flow laterally off‐site. The most significant hazard represented by the spill is the potential for contamination of future water supply wells that may be placed near the site or aquifer contamination that could result if future drilling provides pathways for contaminants through poorly sealed wells or test h

ISSN:0043-1397    

DOI:10.1029/WR018i003p00535

年代:1982

数据来源: WILEY