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排序方式: 共有9497条查询结果,搜索用时 15 毫秒
941.
942.
943.
黄河断流与黄河的水资源承载力 总被引:2,自引:0,他引:2
分析了黄河断流的时空特征、根源和危害,提出了水资源承载力的概念。黄河的水资源承载力即指在生态系统良性循环的条件下,黄河对人类取用水资源的最大承受能力。只有建立起水资源承载力的概念,人类才会谨慎地取用水资源,小心地保护水资源。 相似文献
944.
The Earth may be largely covered with water, but over one billion people are estimated to be without safe drinking water and almost 2.5 billion (40% of the world's population) without adequate sanitation at the outset of the new millennium. The provision of safe water and sanitation for all poses several serious institutional and economic challenges at international, national and local levels. Despite the various political commitments made from the late 1970s onwards, these commitments have remained largely unfulfilled. Even though some efforts to expand coverage have been made over the past two decades, much of those efforts have been undermined by socioeconomic problems and growing population, particularly in the urban areas of developing countries. The water supply and sanitation sector is actually in acute need of new investments for expansion and maintenance of facilities. Nonetheless, some positive trends can be discerned, such as, for example, the increasing recognition of integrated water resources management, environmental sanitation, public-private partnerships and women as a key for improvement and expansion of services. 相似文献
945.
岷江生态环境问题及其对策研究 总被引:1,自引:0,他引:1
本文主要探讨岷江流域的生态环境问题及其对策。全文分为两个部分。(1)研究岷江生态环境问题;(2)解决岷江生态环境问题的主要对策。 相似文献
946.
充分利用水资源 改善生态环境 总被引:1,自引:0,他引:1
本文结合攀枝花地区实际,论述了水资源利用率高低是影响经济发展和改善生态环境的重要因素,调查分析了攀枝花地区水资源利用率低的原因;提出了提高水资源利用率的对策和措施。为促进经济发展和改善生态环境提供了依据。 相似文献
947.
The article describes the historical development of water tariff policy in Tanzania from the colonial times to present. After
gaining independence, the country introduced “free” water policy in its rural areas. Criticism against this policy was expressed
already in the 1970s, but it was not until the late 1980s that change became unavoidable. All the while urban water tariffs
continued to decline in real terms. In rural and periurban areas of Tanzania consumers often have to pay substantial amounts
of money for water to resellers and vendors since the public utilities are unable to provide operative service. Besides, only
a part of the water bills are actually collected. Now that the free water supply policy has been officially abandoned, the
development of water tariffs and the institutions in general are a great challenge for the country. 相似文献
948.
David Pimentel 《Journal of Agricultural and Environmental Ethics》1993,6(1):53-60
The use of organic farming technologies has certain advantages in some situations and for certain crops such as maize; however, with other crops such as vegetables and fruits, yields under organic production may be substantially reduced compared with conventional production. In most cases, the use of organic technologies requires higher labor inputs than conventional technologies. Some major advantages of organic production are the conservation of soil and water resources and the effective recycling of livestock wastes when they are available. 相似文献
949.
Donald E. Evenson Joe C. Moseley 《Journal of the American Water Resources Association》1970,6(5):725-736
A set of simulation and optimization tools capable of analyzing the development and operation of a complex, multi-basin, interconnected water resource are explained. These models provide valuable information regarding the important questions: (1) “When should new projects be build?” (2) “How big should they be?” and (3) “How should the system be operated?” Since these tools were developed by and for practicing engineers, their applicability to real-world problems is mandatory. To assure this, testing was done on an actual proposed project, the Texas Water System. 相似文献
950.
Patrick Mann 《Journal of the American Water Resources Association》1973,9(5):976-984
ABSTRACT: The regulatory process such as that for water rates can be viewed as a bargaining process between regulators, utility management, and consumers. This bargaining process involves both political and economic influences. In an attempt to empirically verify that utility rates are a product of both economic and political factors, a sample of publicly-owned water utilities was subjected to regression analysis. As expected, cost and cost-related factors were positive and significant determinants of residential water rates. Using an admittedly imperfect measure of residential user political influence, there was evidence that increased political activity results in lower water rates. Furthermore, the political influence and water rate linkage is more evident in small water utilities than in larger suppliers. 相似文献