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171.
Sensitivity indices, which rank factors pertinent to surface and subsurface runoff pathways, were used to identify phosphorus
source areas in riparian zones of 15 northern Minnesota lakes. Watershed models were first developed using a geographic information
system (GIS). Empirical models were then developed correlating water quality with land use, lake morphometry, and riparian
sensitivity. Base models of forested, cultivated, pasture/open, wetland and residential land use within 100, 200, 400, and
2000 m of the study lakes were regressed on total phosphorus and chlorophyll-a. Area-weighted groundwater and surface runoff sensitivity indices were then incorporated into each model and tested for significance.
Within the 200-m buffer, the total phosphorus base model was improved by including the groundwater index alone. The chlorophyll-a base model at 200 m was improved by including: (1) the groundwater index alone, and (2) both the groundwater and surface
runoff sensitivity indices. Results suggest that surface and subsurface runoff analysis of potential source areas can improve
decision making for lake riparian management. 相似文献
172.
Lakes Manapouri and Te Anau, in Fiordland National Park, became the center of a major controversy after the New Zealand government offered their water resource to an overseas aluminum smelting consortium for electricity generation. Although the scheme proceeded, the lake levels were not raised as originally proposed. Rather, government sought guidelines to optimize hydroelectric potential while maintaining ecological stability of the vulnerable, largely forested, glaciated lakeshores. Guidelines were derived by relating the vegetation zonation to the natural lake-level fluctuations recorded daily for 37 years. Ahigh operating range in the upper third of the lakes' natural ranges, based on flood tolerances of the woody shoreline species, restricts both duration and frequency. Alow operating range (ca. lower third) safeguards stability of shoreline sediments by limiting drawn-down rates, duration, and frequency. Themain operating range (ca. middle third) has few limitations. These guidelines, which allow utilization of ca. 93% of the water resource, have now been verified by instances of flooding and draw-down rates that exceeded the natural rates recorded earlier. The guidelines were officially accepted by the government in 1977 as a basis for managing the valuable multiple resources of these two lakes and their environs, and they were formalized in legislation in 1981. The details and merits of the guideline approach are discussed. 相似文献
173.
174.
A. L. Jensen 《Environmental management》1984,8(2):135-140
Conventional surplus production models indicate that destruction of fish populations by overfishing is difficult, if not impossible, but catastrophic declines in abundance of exploited populations are common. Surplus production models also do not predict large continuing fluctuations in yield, but large fluctuations in yield are common. Conventional surplus production models assume that fisheries do not impact the population's capacity to increase, but changes in age structure or a decrease in age-specific fecundity resulting from fishing can decrease the coefficient of increase. A surplus production model is developed in which fishing reduces the capacity of a population to increase; the model is applied to describe the fluctuations observed in yield of lake herring (Coregonus artedii) from the upper Great Lakes. The fisheries of the Great Lakes were decimated by the combined effects of heavy fishing and a changing environment. For some species, yield increased to high levels and then the fisheries collapsed; for other species, yield and effort fluctuated greatly. 相似文献
175.
176.
方至 《中国环境管理干部学院学报》1999,(3)
本文分析了洞庭湖流域生态环境破坏对洪涝造成的影响,指出流域生态环境受到破坏主要是人类违背自然规律、破坏森林植被、盲目围湖造田、生产及建设性破坏河道及湖滩所致。文章还就根治洞庭水患的关键性措施——搞好生态恢复,提出了几点意见。 相似文献
177.
揭开武汉东湖蓝藻水华消失之谜 总被引:115,自引:3,他引:112
水华(亦称湖靛)是湖泊富营养化最恶劣的表征之一。武汉东湖70年代至1984年间每年夏季出现蓝藻水华,1985年起突然消失,至今已有14年没有重现,原因何在?通过三次设在湖里的围隔试验,证明鲢鳙的大量放养,是水华消失的决定性因素。 相似文献
178.
Lake Erie water quality has improved dramatically since the degraded conditions of the 1960s. Additional gains could be made,
but at the expense of further investment and reductions in fishery productivity. In facing such cross-jurisdictional issues,
natural resource managers in Canada and the United States must grapple with conflicting objectives and important uncertainties,
while considering the priorities of the public that live in the basin. The techniques and tools of decision analysis have
been used successfully to deal with such decision problems in a range of environmental settings, but infrequently in the Great
Lakes. The objective of this paper is to illustrate how such techniques might be brought to bear on an important, real decision
currently facing Lake Erie resource managers and stakeholders: the choice of new phosphorus loading targets for the lake.
The heart of our approach is a systematic elicitation of stakeholder preferences and an investigation of the degree to which
different phosphorus-loading policies might satisfy ecosystem objectives. Results show that there are potential benefits to
changing the historical policy of reducing phosphorus loads in Lake Erie. 相似文献
179.
目前,巢湖流域非点源污染问题突出。着眼于畜牧业和环境的协调发展,通过对研究区畜牧业生产的实地考查、分析和计算得出结论:畜牧业生产的快速发展、不合理和未加利用的畜牧粪便及畜牧业产品生产加工过程中产生的有机污物是巢湖流域非点源污染的重要原因,来源于畜牧业生产的非点源污染的氮就足以使巢湖水质劣于Ⅲ类标准。最后探讨了解决巢湖富营养化的控制措施。 相似文献
180.
巢湖作为安徽省境内的一个重要湖泊,对安徽省生态环境起到一定的影响作用。蒸发量是影响生态环境的重要因子,在很多方面是该区生态环境的一个反映。采用了统计学方法,对巢湖流域15个蒸发点20年(1981-2000年)的资料进行了分析,初步探讨了巢湖流域的蒸发量空间分布特征与地势、气温、风速、降水量等因子的关系,以及蒸发量在1年内的变化特征和年际变化趋势,试图说明研究时段内人类活动对区域蒸发量的影响。研究表明,由于地形等因素的影响,巢湖流域的蒸发量空间分布不均衡,在研究时段内蒸发量大体呈上升趋势。 相似文献