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731.
Steven R. Abt Christopher I. Thornton Terry L. Johnson 《Journal of the American Water Resources Association》1995,31(1):53-57
ABSTRACT: A study was conducted to derive a simple procedure for estimating the tributary drainage area that may potentially develop at the base of a uniformly graded, steep slope. Data were extracted from a nil development flume study in which 112 rills and their tributary drainage areas were documented. The tributary drainage area for each rill was correlated to the slope length and the slope gradient. The findings are considered applicable to planar, convex, and divergent slopes with lengths of up to 130 m. Field verification is needed to extend the applicability of the relation. 相似文献
732.
Because the agriculture/food sectors appear to be driven by short-term economic and political forces, cheap energy, and agricultural-chemical technologies, waste and environmental/social problems in the agricultural/food sectors are estimated to cost the nation at least $150 billion per year. Most of the waste and environmental/social problems can be eliminated through better resource management policies and the adoption of sustainable agricultural practices.Based on a paper entitled Waste in U.S. Agricultural and Food Sectors—Environmental and Social Costs presented at the Gross National Waste Product Forum, Washington, D.C. 相似文献
733.
Sherwood C. McIntyre James W. Naney 《Journal of the American Water Resources Association》1990,26(2):227-232
ABSTRACT: The three basins of Reelfoot Lake, which is located in northwestern Tennessee, were investigated using the Cs-137 tracer technique to determine rates of sediment deposition and to estimate the time before the basins will fill with sediment. Blue Basin, the largest of the three basins with 2922 ha, had an average annual sedimentation rate of 0.9 cm/yr from 1984 to 1984. The basin will become too shallow for most boating and recreational activities in about 200 years. Buck Basin, the central basin with 774 ha, had an average annual sedimentation rate of 1.1 cm/yr and will become too shallow for most recreational uses in about 100 years. Upper Blue Basin, the most upstream and smallest basin with 439 ha, had an average annual sedimentation rate of 1.7 cm/yr and will become too shallow for most recreational uses in about 60 years. Two important sources of sediment to Reelfoot Lake are erosion from a large number of soybean fields and channelization of many of the streams that flow into the lake. Changes in land management that would reduce erosion could increase the time the lake would remain usable for recreational activities. 相似文献
734.
Soil erosion is accelerating in developing countries of Asia, Africa, and Latin America. It has threatened the livelihood
of millions of peasants, for agriculture is their economic mainstay. A probe into the forces causing erosion reveals that
the elite’s resolve to accumulate ever more wealth and to maintain, consolidate, or expand their sociopolitical power and
the necessity of the poor to fulfill their requirements of food, fuelwood, and fodder are the two major factors accelerating
soil erosion. Unless the vast masses of poor people are integrated into the national mainstream through the implementation
of equitable and redistributive development policies, it is impossible to control the accelerating rate of soil erosion and
thus to achieve the objective of sustainable development.
In this article, the phenomenon “soil erosion” is studied with the sol e focus on causation through anthropogenic factors. 相似文献
735.
黄土丘陵沟壑区土壤侵蚀专家系统试验研究 总被引:6,自引:0,他引:6
本文介绍了黄土丘陵的沟壑区土壤侵蚀专家系统的建造原理与方法.系统采用压缩编码方式存贮各种地学图形与遥感图象数据,具有效据与图象的存贮更新、查询检索、分析处理、图象显示和自动制图功能.该系统可对黄土地区的土壤侵蚀进行准确、快速的预测、预报,并对土壤侵蚀的综合治理,水土保持规划提出几种可行性建议供用户选择。用该系统对山西省离石县王家沟流域羊道沟的土壤侵蚀进行了试验研究,并对试验结果进行了系统评价。 相似文献
736.
毁林与汉代居延垦区的衰落 总被引:1,自引:0,他引:1
本文根据历史史料,阐明了汉代居延垦区由兴旺发达到衰落的历史原因。进一步说明了乱破滥伐森林带来的恶果。开发大自然必须遵循自然规律,切不可盲目蛮干,毫无克制。 相似文献
737.
738.
Fritz M. Roka Billy V. Lessley William L. Magette 《Journal of the American Water Resources Association》1989,25(4):821-827
ABSTRACT: Utilizing predictions of pollutant movement generated by the CREAMS model, the economics of reducing field losses of sediment and nitrate percolation were compared between two soil types on each of two slopes common to the Upper Eastern Shore of Maryland. The soils considered were Matapeake silt loam and Sassafras sandy loam textures on field slopes of 3.5 percent and 7.5 percent. A representative cash grain farm was used as a basis of comparison. Under assumptions of profit maximization, economic optimal cropping systems varied by slope. Results further indicated that relative cost-effectiveness of sediment or nitrate percolation control varied by soil type for both slopes considered. Unit costs of sediment control were less on silt loam soils, while unit costs of nitrate percolation control were less on sandy loam soils. 相似文献
739.
740.
区域开发建设会对生态环境造成一定程度的破坏。利用一些简单适用的模型或参数,对珠江温泉城开发中的主要生态因子进行了量化研究,结果表明珠江温泉城水土流失增加、绿量减少、林地的景观优势度降低。依据开发前后的变化结果,确定了补偿其开发应该采取的具体对策。 相似文献