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341.
Water is scarce in many regions of the world, clean water is difficult to find in most developing countries, there are conflicts
between irrigation needs and urban demands, and there is wide debate over appropriate means of resolving these problems. Similarly,
in China, there is limited understanding of the ways in which people, groups, and institutions contribute to, are affected
by, and respond to changes in water quantity and quality. We use the example of the Yellow River basin to argue that these
social, managerial, and policy dimensions of the present water problems are significant and overshadow the physical ones.
Despite this, they receive relatively little attention in the research agenda, particularly of the lead agencies in the management
of the Yellow River basin. To this end, we ask ten research questions needed to address the policy needs of water management
in the basin, split into two groups of five. The first five relate to the importance of water in this basin and the changes
that have affected water problems and will continue to do so. The second five questions represent an attempt to explore possible
solutions to these problems. 相似文献
342.
Jon C. Gottschalck Robert R. Gillies 《Journal of the American Water Resources Association》2001,37(2):305-314
ABSTRACT: Increased carbon dioxide in the atmosphere has the secondary effect on plants of reducing transpiration. The degree of reduction in transpiration has been studied mostly at the leaf scale and as such, has not taken feedbacks into account that come into play when the plant canopy or the atmosphere as a whole is considered. The objective of this paper is to examine the role of negative feedback processes that act through the dynamics of the canopy and the atmosphere. This is done through the application of two canopy models, one of which is later coupled to a full Atmospheric General Circulation Model (AGCM) called GENESIS. The results suggest that the reduction in transpiration in a double CO2 environment compared to present day will not be as considerable as the leaf scale experiments suggest ‐ a 7 percent reduction compared to 15 to 57 percent when feedbacks are considered. At the regional scale, precipitation patterns appear to be the primary factor in determining evapotranspiration. The implications for agriculture, in terms of water usage, would therefore not seem to be as acute as the leaf scale experiments depict. Regarding climate change, there is a suggestion that regional water usage may vary from present day values in certain areas. 相似文献
343.
344.
Andrew E. Derocher Magnus Andersen Øystein Wiig Jon Aars 《Behavioral ecology and sociobiology》2010,64(6):939-946
We assessed the role of size, mass, and age in mating and non-mating polar bears (Ursus maritimus) at Svalbard, Norway, during the spring breeding season. The ratio of male to female mass, in male-female pairs, ranged from
1.00 to 3.02 ([`(x)] = 1.99 \overline x = 1.99 ) indicating that mating males were larger than mating females but with substantial variation. Paired males were older than
unpaired males and male mass was related to age. However, males paired with females were not significantly different in body
mass from those males caught alone. Wounds and scars resulting from fights between males began at about 6 years of age and
peaked at about 17 and 20 years of age, respectively. The frequency of broken canines in males, presumably due to increased
male-male conflicts, increased with age but showed little increase in females. The wide range of male size in male-female
pairs and the age-related signs of injury suggest that male polar bears engage in both scramble competition and contest competition
for access to breeding females. The mating system of polar bears is variable but is best described as female defense polygyny
or serial monogamy. 相似文献
345.
Jon L. Pierce 《组织行为杂志》1984,5(2):147-154
This study is a constructive replication of investigations into the technology-job design relationship. It is hypothesized that the utilization of a preprogrammed/system controlled technology reduces environmental variance resulting in routine (simple) versus non-routine (complex) job designs. Empirically it was noted that employees perceive and describe their jobs as routine when they interact with a system controlled technology. 相似文献
346.
Landcare GIS: Evaluating Land Management Programs in Australia 总被引:1,自引:0,他引:1
347.
Kenneth E McConnell Jon G Sutinen 《Journal of Environmental Economics and Management》1979,6(2):127-139
The theory of recreational fishing is developed and conditions are derived for optimal management policy, with special attention given to functional relationships that must be empirically verified. Determinants of the optimal allocation between commercial and recreational fishing effort are derived. The theory is extended to include selected peculiar features of recreational fishing: Some anglers sell their catch; a small proportion of the fishing population accounts for a large proportion of the catch; and anglers throw back a fraction of what they catch. Optimal policies are derived under these more realistic conditions. 相似文献
348.
An increasing number of scholars and practitioners have emphasized the importance of ‘feelings of ownership’ for the organization (even when employees are not legal owners). In this exploratory study, we examine the relationships of psychological ownership with work attitudes and work behaviors. We start by developing hypotheses based on the psychology of possession and psychological ownership literatures. We then test these hypotheses with data from three field samples, using responses from over 800 employees, as well as manager and peer observations of employee behavior. Results demonstrate positive links between psychological ownership for the organization and employee attitudes (organizational commitment, job satisfaction, organization‐based self‐esteem), and work behavior (performance and organizational citizenship). More important, psychological ownership increased explained variance in organization‐based self‐esteem and organizational citizenship behavior (both peer and supervisor observations of citizenship), over and above the effects of job satisfaction and organizational commitment. Contrary to prior theoretical work on psychological ownership, results, however, fail to show an incremental value of psychological ownership in predicting employee performance. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
349.
Magne Wathne Charles S. ReVelle Jon C. Liebman 《Journal of the American Water Resources Association》1975,11(3):536-545
ABSTRACT: The planning of water supply reservoirs has traditionally been based on the Rippl or sequent peak analysis which applies to the design of a single reservoir. This paper incorporates the sequent peak method as the central feature in establishing a procedure for determining the sizes of several potential reservoirs located in a system of one or more rivers. Separate algorithms are developed for sites on parallel streams and for sites on the same stream. In both cases the approach is to find the combination of reservoirs which can satisfy a given constant monthly demand at a minimum total construction cost. It is shown that both problems can be cast in the form of a dynamic programming problem. A more complex system is then a combination of reservoirs in parallel and in series. An extension is given if the monthly demand is not constant but each reservoir satisfies a constant fraction of the monthly demand. 相似文献
350.
Matt Grove Jon Harbor Bernard Engel 《Journal of the American Water Resources Association》1998,34(5):1015-1023
ABSTRACT: The U.S. Department of Agriculture Curve Number (CN) method is one of the most common and widely used techniques for estimating surface runoff and has been incorporated into a number of popular hydrologic models. The CN method has traditionally been applied using compositing techniques in which the area weighted average of all curve numbers is calculated for a watershed or a small number of sub-watersheds. CN compositing was originally developed as a time saving procedure, reducing the number of runoff calculations required. However, with the proliferation of high speed computers and geographic information systems, it is now feasible to use distributed CNs when applying the CN method. To determine the effect of using composited versus distributed CNs on runoff estimates, two simulations of idealized watersheds were developed to compare runoff depths using composite and distributed CNs. The results of these simulations were compared to the results of similar analyses performed on an urbanizing watershed located in central Indiana and show that runoff depth estimates using distributed CNs are as much as 100 percent higher than when composited CNs are used. Underestimation of runoff due to CN compositing is a result of the curvilinear relationship between CN and runoff depth and is most severe for wide CN ranges, low CN values, and low precipitation depths. For larger design storms, however, the difference in runoff computed using composite and distributed CNs is minimal. 相似文献