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31.
J. C. Day 《Journal of the American Water Resources Association》1972,8(5):935-947
ABSTRACT. Despite radical differences in water laws, water management agencies, approaches to water planning, and financial resources, Mexico and the United States forged a common program to manage water and related land on the Rio Grande. Actions of Rio Grande Commissions related to stream gaging, boundary definition, and multiple-purpose construction projects are among the more successful international water-management efforts in the world. Cost-sharing arrangements promoted rapid completing of international works. However, joint action accomplished only part of expectations. International developments were competitive rather than complementary until basin water appropriation was virtually complete. Moreover, Commissions were not empowered to consider long-range competitive water needs, or regional water requirements, throughout the basin. International groundwater use coordination does not exist. International structures produce less than anticipated benefits. Hydroelectric generators are financial liabilities, irrigated acreage exceeds dependable streamflow, and soil salinization is experienced. Unanticipated environmental changes occurred in every major program. The Rio Grande experience points to the need for society to specify goals to which the use of water should contribute and to specify priorities for water use among different sectors of river basins and various segments of society. 相似文献
32.
The objective of this work is to investigate the horizontal stretching effect of ground on high-pressure vapor jet of LNG tank leakage near the ground. A numerical model for leakage jet was developed and several series of leakage scenarios were theoretically analyzed for different heights of the tank orifice, inner pressures and outer temperatures. The results show that the near ground plays an important role in the horizontal transportation of LNG leakage vapor. The corresponding danger distance is surprisingly lengthened because of the horizontal stretching of leakage vapor cloud by the ground nearby, especially for those cases with a lower orifice on tank. It is illustrated that there is an obvious change for the central axis track, gas concentration and velocity of the jet in the far-field during the jet is touching the ground. In addition, the dimensionless analyses on the dependence of gas concentration, velocity and gas concentration on the transportation distance indicated that there were two stages of deflection behaviors of the jet. Finally, the enlarged danger distance by the horizontal stretching for the LNG tank leakage with a low orifice indicated the more dangerous scene of those leakage close on ground. The data and revelation here about the danger area prediction can be an important guide for the emergency management during the LNG tank leakage accidents. 相似文献
33.
34.
Turbulence characteristics within sparse and dense canopies 总被引:2,自引:0,他引:2
Laurence Pietri Alexandre Petroff Muriel Amielh Fabien Anselmet 《Environmental Fluid Mechanics》2009,9(3):297-320
Boundary layer interactions with canopies control various environmental processes. In the case of dense and homogeneous canopies,
the so-called mixing layer analogy is most generally used. When the canopy becomes sparser, a transition occurs between the
mixing layer and the boundary layer perturbed by interactions between element wakes. This transition has still to be fully
understood and characterized. The experimental work presented here deals with the effect of the canopy density on the flow
turbulence and involves an artificial canopy placed in a fully developed turbulent boundary layer. One and two-component velocity
measurements are performed, both within and above the canopy. The influence of the spacing between canopy elements is studied.
Longitudinal velocity statistical moments and Reynolds stresses are calculated and compared to literature data. For spacings
greater than the canopy height, evidences of this transition are found in the evolution of the skewness factor, shear length
scale and mixing length. 相似文献
35.
36.
Christine Schonewald-Cox Marybeth Buechner Raymond Sauvajot Bruce A. Wilcox 《Environmental management》1992,16(2):273-282
Protecting biodiversity on public lands is difficult, requiring the management of a complex array of factors. This is especially
true when the ecosystems in question are affected by, or extend onto, lands outside the boundaries of the protected area.
In this article we review recent developments in the cross-boundary management of protected natural resources, such as parks,
wildlife reserves, and designated wilderness areas.
Five ecological and 11 anthropic techniques have been suggested for use in cross-boundary management. The categories are not
mutually exclusive, but each is a distinct and representative approach, suggested by various authors from academic, managerial,
and legal professions. The ecological strategies stress the collection of basic data and documentation of trends. The anthropic
techniques stress the usefulness of cooperative guidelines and the need to develop a local constituency which supports park
goals.
However, the situation is complex and the needed strategies are often difficult to implement. Diverse park resources are influenced
by events in surrounding lands. The complexity and variability of sources, the ecological systems under protection, and the
uncertainty of the effects combine to produce situations for which there are no simple answers. The solution to coexistence
of the park and surrounding land depends upon creative techniques and recommendations, many still forthcoming. Ecological,
sociological, legal, and economic disciplines as well as the managing agency should all contribute to these recommendations.
Platforms for change include legislation, institutional policies, communication, education, management techniques, and ethics. 相似文献
37.
采用构造体素法(CSG)/边界表示法(Breps)混合式表示模式来完成冲裁零件的几何造型,具有实时显示、高效输入的优点。结合双向循环链表和二叉树这2种数据结构有效表征了包含冲栽件图形几何信息与拓扑信息的数字模型。从而为面向工程的模具CAD/CAPP/CAM集成提供了理论上和技术上的可靠基础。 相似文献
38.
铁岭市各类大气污染源浓度贡献分析 总被引:2,自引:0,他引:2
利用铁岭市2004年的PM10(可吸入颗粒物)和SO2(二氧化硫)大气环境监测资料、污染源排放清单资料和气象资料,以及AERMOD模型(1)进行了铁岭市大气环境质量区域评价。结果表明:铁岭市低架源对地面浓度的贡献较大,高架源对地面浓度的贡献相对较小。 相似文献
39.
评估是一种权力。各类"评估"实际上都代表了其主管部门的权力和利益,甚至沦为各部门争夺话语权、攫取部门利益的一道关卡。多种评价"混战",不仅评价内容重复、程序烦琐、浪费人力和资源,同时评价背后代表其主管部门的利益和权力,评价的"混战"也成为各部门维护自身利益、争夺话语权的"混战"。本文在对现有评价制度、实施情况、存在问题的剖析的基础上,基于协同推进生态文明建设的要求,提出横向上协同相关部门、纵向上协同国家和地方、政府和市场、政策规划与项目等重大决策的多评融合实施路径,最后提出了多评融合的四项政策建议。 相似文献
40.
Leo X. C. Dutra Nick Ellis Pascal Perez Cathy M. Dichmont William de la Mare Fabio Boschetti 《Ambio》2014,43(8):1069-1081
This article analyzes interviews with natural resource managers in South East Queensland (SEQ), Australia. The objectives of the research are (i) to apply and test deductive/inductive text analysis methods for constructing a conceptual model of water quality decision-making in SEQ, (ii) to understand the role of information in the decision-making process, and (iii) to understand how to improve adaptive management in SEQ. Our methodology provided the means to quickly and objectively explore interview data and also reduce potential subjective bias normally associated with deductive text analysis methods. At a more practical level, our methodology indicates potential intervention points if one is to influence the decision-making process in the region. Results indicate that relevant information is often ignored in SEQ, with significant consequences for adaptive management. Contextual factors (political, social, and environmental) together with effective communication or lobbying strategies often prevent evidence-based decisions. We propose that in addition to generating information to support decisions, adaptive management also requires an appraisal of the true character of the decision-making process, which includes how stakeholders interact, what information is relevant and salient to management, and how the available information should be communicated to stakeholders and decision-making bodies.