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51.
根据全国生态环境保护“十五”计划要求,在计划期间力争60%的小城镇完成环境保护规划,广西小城镇由于经济发展不平衡,部分小城镇还比较落后,且存在较多的环境问题,目前小城镇的环境保护规划尚未得到有效的开展,因此应及时找出问题和差距,并根据存在的问题作出相应的对策,在计划期内是可以完成小城镇环境保护规划的目标,为广西小城镇的可待续发展提供环境保障。 相似文献
52.
Traditional Land-Use Systems and Patterns of Forest Fragmentation in the Highlands of Chiapas, Mexico 总被引:1,自引:0,他引:1
Ochoa-Gaona S 《Environmental management》2001,27(4):571-586
The influence of slash-and-burn agriculture and tree extraction on the spatial and temporal pattern of forest fragmentation
in two municipalities in the highlands of Chiapas, Mexico was analyzed. The data series were derived from two subsets of satellite
images taken in 1974 and 1996. The analysis was based on area, edge, shape, core area, and neighbor indices. During the 22
years, the dense forest decreased by 8.9%/yr in Huistán and by 8.6%/yr in Chanal, while open/disturbed forest, secondary vegetation,
and developed area increased in both municipalities. The total number of fragments increased by 1.4%/yr and 2.3%/yr in Huistán
and Chanal, respectively. Dense forest showed the highest increase in the number of fragments (6%/yr in Huistán and 12%/yr
in Chanal), while edge length, core area, and number of dense forest core areas decreased. The larger fragments of dense forest
present in 1974 were divided into smaller fragments in 1996; at the same time, they experienced a process of degradation toward
open/disturbed forest and secondary vegetation. Two different fragmentation patterns could be distinguished based on agricultural
or forestry activities. Forest fragmentation did not occur as a continuous process; the pattern and degree of fragmentation
were functions of land tenure, environmental conditions, and productive activities. The prevalence of rather poor soil conditions,
small-holdings, growing human population densities, increasing poverty, and the absence of alternative economic options will
maintain a high rate of deforestation and forest fragmentation in the studied region. 相似文献
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54.
E. C. Dickey J. K. Mitchell J. N. Scarborough 《Journal of the American Water Resources Association》1979,15(6):1753-1769
ABSTRACT: The application of hydrologic models to small watersheds of mild topography is not well documented. This study evaluates the applicability of hydrologic models described by Huggins and the Soil Conservation Service to small watersheds by comparing the simulated and actual hydrograph for both gaged and ungaged situations. The annual maximum rainfall events plus storms exceeding 2.5 inches from 25 years of rainfall and runoff data for two small watersheds were selected for the model evaluations. These storms had a variety of patterns and occurred on many different watershed conditions. Simulated and actual hydrographs were compared using a parameter which contained volume, peak, and shape factors. One-half of the selected storms were used to calibrate the models. For both models, there were no significant differences between the simulated and actual runoff volumes and peak runoff rates. Parameters obtained during the calibration process and relationships developed to estimate antecedent moisture and to modify tabulated runoff curve numbers were used to simulate the runoff hydrograph from the remaining storms. These remaining storms or test storms were simulated only once in order to imitate an ungaged situation. In general, both the Huggins and SCS model performed similarly on the test storms, but the level of model performance was lower than that for the calibration storms. For both models, the two-day antecedent rainfall was more important than the five-day in determining antecedent moisture and modifying tabulated curve numbers. The time of concentration which resulted in good hydrograph simulations was about three times larger than that estimated using published empirical relationships. 相似文献
55.
Timothy R. Lazaro 《Journal of the American Water Resources Association》1977,13(1):149-151
ABSTRACT: Small, rural communities (less than 2500 population) in general do not have governmental staffs with the breadth required to satisfactorily implement and enforce a drainage ordinance. This fact has serious implications in rural Planning. Within a six-country rural area of Southwest Virginia, the circuit riding town manager program has been successfully conducted. The circuit riding town manager is a planning staff member who acts in the capacity of a town manager (assistant to the mayor) for five small towns, any one of which alone could not afford to support the services of such a professional. This note recommends that a circuit riding technical ordiance administrator program could be developed along the same lines. In this manner, the technical ordinance program for serveral small communities could be successfully implemented. 相似文献
56.
Pamela A. Heidell Paul H. Kirshen 《Journal of the American Water Resources Association》1982,18(1):105-110
ABSTRACT: The potential for hydroelectric power development at existing dams is great in oil dependent New England where there are over 10,000 dams presently in existence. Over 400 developments have been proposed in the region, the majority of which are small scale, and do not have major environmental impacts. Nevertheless, a variety of constraints may hinder development. A study of three efforts by municipalities in unique positions to develop hydropower reveals that organizational and political considerations are significant factors affecting development. Successful hydropower development requires: (1) the cooperation and interaction of citizens, government, and the private sector; (2) community interest and education; and (3) strong resolve. 相似文献
57.
58.
J. Mistry 《Journal of environmental management》1998,54(4):321-334
Today, fire in the Braziliancerrado(savanna) is predominantly caused by farmers. They use fire during the dry season to promote fresh grass regrowth in pastures for their cattle and to clear areas of planting ready for cultivation in the wet season. This study researched fire use by farmers in thecerradoof the Distrito Federal, central Brazil, in order to investigate what influences their fire management decision-making. The results show that the two main factors limiting the choice of feasible options for farmers to meet their objectives are income and time. However, perceptions also play a major role in the decision-making process, and for many farmers this alone determines whether fire is used. Various fire practices involved with timing, frequency and size, as well as precautions taken before and during the burn, and the factors influencing these decisions are presented. This study shows that it is vital to understand factors determining fire use if effective fire management plans and policies are to be developed.1998 Academic Press 相似文献
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