摘要:

A model for optimizing short‐, intermediate‐, and long‐run irrigation decisions for surface water reservoirs is developed for a river valley irrigation system controlled by one decision maker. The modeled valley is characterized by highly variable reservoir inflows and crop growing conditions, and irrigable land supplies which are plentiful relative to available water. It advances similar work of the early 1970s pertaining to a corn monoculture by using a complex soil water‐plant growth simulation model for cotton developed by crop scientists over a number of years, and by employing an extra simulation model to simulate the effects of using optimal decisions derived by dynamic programming. The results indicate a potential for disagreement about reservoir management strategies and level of irrigation development between irrigators, other members of the local economy, and national economy policy makers. The assumption of one decision maker internalizes the derivation and communication of supply and demand probabilities, giving the results a level of economic efficiency which makes them a standard against which to judge the results of decentralized

ISSN:0043-1397    

DOI:10.1029/WR024i005p00633

年代:1988

数据来源: WILEY

摘要:

Previous models optimize short‐, intermediate‐, and long‐run irrigation decision making in a simplified river valley system characterized by highly variable water supplies and demands for a single decision maker controlling both reservoir releases and farm water use. A major problem in relaxing the assumption of one decision maker is communicating the stochastic nature of supplies and demands between reservoir and farm managers. In this paper, an optimizing model is used to develop release rules for reservoir management when all users share equally in releases, and computer simulation is used to generate an historical time sequence of announced releases. These announced releases become a state variable in a farm management model which optimizes farm area‐to‐irrigate decisions through time. Such modeling envisages the use of growing area climatic data by the reservoir authority to gauge water demand and the transfer of water supply data from reservoir to farm managers via computer data files. Alternative model forms, including allocating water on a priority basis, are discussed briefly. Results show lower mean aggregate farm income and lower variance of aggregate farm income than in the single decision‐maker case. This short‐run economic efficiency loss coupled with likely long‐run economic efficiency losses due to the attenuated nature of property rights indicates the need for quite different ways of integrating reservoir and

ISSN:0043-1397    

DOI:10.1029/WR024i005p00641

年代:1988

数据来源: WILEY

摘要:

The concept of a water use property right is developed which does not apply to water volumes as such but to a share of the capacity (not contents) of river storage reservoirs and their inflows. The shareholders can withdraw water from their share over time in accordance with their preferences for stability of water deliveries. The reservoir authority does not manage reservoir releases but keeps record of individual shareholder's withdrawals and net inflows to monitor the quantity of water in each shareholder's capacity share. A surplus of total reservoir contents over the sum of the contents of the individual shareholder's capacity shares will accrue over time. Two different criteria for its periodic distribution among shareholders are compared. A previous paper Dudley (this issue(b)) noted a loss of short‐run economic efficiency as reservoir and farm management decision making become separated. This is largely overcome by capacity sharing which allows each user to integrate the management of their portion of the reservoir and their farming operations. The nonattenuated nature of the capacity sharing water rights also promotes long‐run economic efficie

ISSN:0043-1397    

DOI:10.1029/WR024i005p00649

年代:1988

数据来源: WILEY

摘要:

The influence of hydrologic processes on Al chemistry was investigated along an elevational gradient in a headwater stream at the Hubbard Brook Experimental Forest. Relationships between streamflow and concentrations of inorganic and organic Al, H+, and dissolved organic carbon varied within the watershed. At high elevations, increased streamflow was associated with reduced surface water acidity and decreased inorganic Al concentrations. At low elevations, however, increased streamflow was associated with increases in stream acidity and concentrations of inorganic Al. Changes in soil flow paths and variations in source areas both appear to regulate stream chemistry. Flow through upper soil horizons under high‐flow conditions appears to be the controlling hydrologic influence on stream chemistry at the high‐elevation site. At the low‐elevation site, contributions of flow from the more acidic, upper region of the watershed during high‐flow conditions appears to be the major hydrologic influence on stream chemistry. During low‐flow conditions the upper reaches of the stream become dry, so that there is no contribution to flow from this part of the watershed. Stream solutions appeared to be closest to equilibrium with respect to natural gibbsite under high‐ and low‐flow conditions, with no indication that changes in flow introduced disequilibrium conditions. Efforts to incorporate hydrologic effects into surface water acidification models must address the relationship between runoff generation mechanisms and spatial variations in watershed bi

ISSN:0043-1397    

DOI:10.1029/WR024i005p00659

年代:1988

数据来源: WILEY

摘要:

A two‐dimensional “inverse” or “parameter estimation” code was developed for use in the Basalt Waste Isolation Project site characterization program. The method uses a sequential least squares algorithm that incorporates a finite element groundwater flow code. Adjoint equations and flow equations are solved to provide an efficient calculation of sensitivity coefficients. The least squares algorithms are formulated to sequentially include the output information for updating a priori parameter estimates. Several cases were studied to demonstrate the methodology developed; included were an analysis of pumping from a single well and a sequential analysis in which results obtained by pumping from one well were combined with an analysis of pumping from a second well. The approach emphasizes the sequential nature of the problem whereby the characterization of site hydrology can be systematically

ISSN:0043-1397    

DOI:10.1029/WR024i005p00670

年代:1988

数据来源: WILEY

摘要:

A new analytic function is presented to model three‐dimensional flow near a partially penetrating well. The function represents a sink distribution along the well axis, whereby equipotential conditions along the well perimeter are approximately satisfied by adjusting several degrees of freedom of the function. This procedure is well known and has led to rather accurate solutions provided a sufficient number of free parameters were incorporated. The values for these parameters are obtained by solving a system of linear equations. The function presented in this paper achieves the same accuracy as past solutions with a significant reduction in the number of degrees of freedom required and hence fewer equations to be solved. This increased efficiency is of little consequence when the well is modeled by itself. However, when combined with the solutions to the many other flow features in a regional aquifer, the savings become significant. In fact, if each of the individual solutions would have many degrees of freedom, the resulting system of equations may become unmanageable, thus restricting applications. To demonstrate the use of the new function, a hypothetical groundwater contamination problem is solved, whereby contaminants are intercepted by a partially penetrating wel

ISSN:0043-1397    

DOI:10.1029/WR024i005p00683

年代:1988

数据来源: WILEY

摘要:

An examination of the calibration aspect of conceptual rainfall‐runoff models was undertaken using the Sacramento soil moisture accounting model and a study comparing the performance of a Newton‐type optimization algorithm with that of a direct search algorithm. Results indicate that the direct search algorithm is the more robust of the two because the Newton‐type algorithm is more susceptible to poor conditioning of the response surface. Graphical studies of the response surface of the model's parameter space confirmed the presence of discontinuities and a rough‐textured surface, particularly in the deri

ISSN:0043-1397    

DOI:10.1029/WR024i005p00691

年代:1988

数据来源: WILEY

摘要:

Watershed liming is one method to decrease the acidity of surface waters. To gain an understanding of the mechanisms involved in terrestrial liming and to develop a tool for planning and evaluation, a mathematical model has been developed. The model includes key chemical processes such as limestone dissolution, cation‐exchange reactions, and leaching and accumulation of dissolved species. The ability of the model to describe the short and long‐term improvement in stream water quality following wetland liming is demonstrated by comparing the model calculations with data from two Swedish full‐scale liming experiments. The influence of temporal hydrological and chemical variations on model output is assessed. The sensitivity of the system response to liming is analyzed with respect to three design parameters: the amount and the fineness of the liming material, and the fraction of the watershed that is treated. The simulations illustrate the importance of careful soil and hydrological characterization of treated watersheds to ensure that the limestome dose and the treated area are sufficient to ensure a satisfactory increase in stream pH and resistance to reacidific

ISSN:0043-1397    

DOI:10.1029/WR024i005p00701

年代:1988

数据来源: WILEY

摘要:

Mathematical model for defining stable width and depth of straight gravel rivers is presented, in which it is revealed that the major agency for maintaining stable channel is lateral diffusion of longitudinal fluid momentum due to turbulence. The primary quantities which determine the stable channel geometry are found to be flow discharge, longitudinal free surface slope, the median size of bed material, and gradation of the bed material. Increasing gradation is found to increase the depth and decrease the width. Introduction of one loose and the other rigid bank in laboratory experiments provides good examples to test the model, in which four kinds of sand were used to test the gradation effect. These laboratory data support the mathematical model presented herein. The theory also performs well when it is applied to natural gravel rivers.

ISSN:0043-1397    

DOI:10.1029/WR024i005p00713

年代:1988

数据来源: WILEY

摘要:

Integrated snowpack samples and lakewater samples were collected from a low‐alkalinity watershed in the North Cascades in 1984 and 1985 and analyzed for inorganic chemical parameters. Mean concentrations of NO3−and SO4−2from North Cascades snowpack were near 4.5 and 5.5 μeq L−1, respectively. MeanpH was 5.2–5.3. During melting, anion levels in the snowpack decreased andpH increased. By July, mean NO3−and SO4−2concentrations were 0.32 and 1.73 μeq L−1, respectively, and meanpH was 5.48. Acid neutralizing capacity at the lake outlet during snowmelt was diluted to 50% of April premelt values. During snowmelt runoff there was no apparent neutralization of bicarbonate by strong acids. By comparing lakewater NO3−concentrations to snowpack concentrations, over 75% of the NO3−in the lake could be attributed to a snowpack source. An estimated 30% of the SO4−2in the lake was de

ISSN:0043-1397    

DOI:10.1029/WR024i005p00723

年代:1988

数据来源: WILEY