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161.
Leonard F. DeBano Burchard H. Heede 《Journal of the American Water Resources Association》1987,23(3):463-470
ABSTRACT: Naturally occurring and man-made structures can be used for enhancing the development of riparian zones. Naturally occurring structures are cienagas, beaver dams, and log steps. Man-made structures include large and small channel structures and bank protection devices. All these structures affect streamflow hydraulics and sedimentation and can create a more favorable environment for riparian zone establishment. However, when they are used improperly, they can be destructive to existing riparian zones. Since stream processes are generally slow, long-time spans may pass before the effects of management action, good or bad, become visible. Also, the effects of large dam installations may appear a long distance downstream from the dam. Therefore, investigations must be of a wide scope. Interactions between riparian site, channel, and streamflow may be so complex that an interdisciplinary approach is required. 相似文献
162.
Leonard J. Kouba 《Journal of the American Water Resources Association》1982,18(6):937-940
ABSTRACT: Fishing is a popular form of recreation in the state of Illinois. Despite seemingly endless varieties of fishing opportunities, limited public access, distant location of lakes with respect to population centers, chemical contaminants in some waters, and the desire for species not naturally found in Illinois have engendered an alternate form of recreational land use, the daily fee fishing area. A fee area is any privately controlled body of water or waters where a fee is charged for fishing. Such operations must Low licensed by the state of Illinois. Fee areas are almost entirely comprised of existing man-made impoundments, particularly farm ponds. They are usually stocked on a put and take basis. The most common species utilized in Illinois are carp and channel catfish. Fee areas are concentrated in the southwestern part of the state and near major metropolitan centers. Even though the number of fee areas has declined during the past decade, the role of such operations remains important to the overall picture of fishing in Illinois. 相似文献
163.
164.
Summary Colonial orb-weaving spiders from Mexico were studied to test predictions of risksensitive foraging theory: 1. group foraging increases prey capture/individual, and reduces prey variance; 2. spiders should be expected to exhibit risk-averse behavior (forage in groups) when the average level of prey exceeds individual needs, and exhibit risk-prone behavior (forage solitarily) when prey are searce. Laboratory and field studies show that group foraging increases capture efficiency and reduces variability in prey captured per spider. In desert/mesquite grassland habitat, where prey availability is low, M. atascadero forage solitarily in most cases. In tropical rainforest/agriculture sites, M. increassata forage in large colonies of thousands of webs. In intermediate habitats, M. spinipes forages solitarily or in groups, depending on prey availability. Over a range of sites with varying levels of prey, M. spinipes shifts from a risk-prone to a risk-averse group foraging strategy as prey increases.Group foraging behavior observed in colonial Metepeira fits the predictions of risk-sensitive foraging models. These findings explain why spiders tend to group webs together only in areas of superabundant prey. The role of risk-sensitivity in the evolution of coloniality in spiders is discussed. 相似文献
165.
Leonard S. Greenberger 《补救:环境净化治理成本、技术与工艺杂志》2016,26(2):121-128
Successful soil remediation depends on many factors that project managers know well: accurate assessments as to the extent and nature of contamination; the right choice and proper implementation of remediation technologies; and, deft negotiation of regulatory requirements and review. One equally important factor that often receives too little attention is stakeholder communication. Effective communication strategies and tactics can help avoid project delays and cost overruns related to stakeholder concerns and opposition, and inoculate owners and others against frivolous litigation. Remediation projects also offer opportunities to bolster the brands and images of engaged parties, including owners, engineering and environmental contractors—and even the regulatory agencies that oversee them. Understanding the skills and techniques necessary to communicate effectively when people are angry, upset, and suspicious of everything you say is essential to project success. This article will explore six rules for effective communication—brought to life by genuine case studies where they have been followed to positive effect—that encapsulate the skills and techniques project managers can apply in difficult situations involving the remediation of contaminated sites. ©2016 Wiley Periodicals, Inc. 相似文献
166.
This article analyzes the effect of market power in the presence of dynamic and biological externalities. When several countries harvest fish in international waters the evolution of fish population is affected by their joint action, thus generating a biological and a dynamic externality. If there is trade, the market-clearing prices depend on the harvesting and consumption in all countries. Therefore, market-clearing prices also generate an externality. We find a subgame perfect Cournot–Nash equilibrium and study the conditions under which it may be efficient. We also analyze the role of different externalities in generating inefficiency. 相似文献
167.
We propose a new method of cost-benefit analysis to investigate whether the new air pollution control equipment-electrocyclone vis-a-vis cyclone has the potential for practical use. When the flow rate of waste gas is 1000 m3/min, the cost of cyclone is then compared with that of electrocyclone provided that the benefit side is being fixed. The results show that the capital cost of electrocyclone is higher than that of cyclone, but the operating cost of electrocyclone is much lower than that of cyclone. Straight-line depreciation method is used to calculate the depreciation of capital cost per year. The total cost of electrocyclone is NT$ 160 290 per year which is cheaper than that of cyclone NT$ 225 356. 相似文献
168.
Susan Seacrest Robert Kuzelka Rick Leonard 《Journal of the American Water Resources Association》2000,36(2):253-263
ABSTRACT: Global climate change is examined from the perspective of its relevancy and urgency as a public policy issue. Interpreting from literature specific to investigations into public awareness and concern, climate change is seen as a legitimate though less than urgent issue. The literature reveals that the general public holds surprising misconceptions about the processes contributing to climate change, including failure to grasp the fundamental connection to CO2. General ambivalence is also suggested from the results of two surveys conducted by The Groundwater Foundation. They first asked participants in a recent Groundwater Guardian Conference to rate levels of discussion and concern for water resources implications in the participants' communities. A second survey polled national water resource organizations about the extent climate change has been a focus of their educational, investigative, or advocacy efforts. The paper concludes by describing basic barriers to stimulating public response to climate change, which education about the issue should address, and by offering a model to educate and involve citizens based on the Groundwater Guardian program developed by the The Groundwater Foundation. 相似文献
169.
Jeffrey L. Hyland Timothy R. Snoots W. Leonard Balthis 《Environmental monitoring and assessment》1998,51(1-2):331-343
A study was conducted to assess the condition of estuaries in the EMAP Carolinian Province (Cape Henry, VA - St. Lucie Inlet, FL). Synoptic measures of sediment contamination, toxicity, and macroinfaunal condition were made at 82 and 86 stations in 1994 and 1995, respectively, in accordance with a probabilistic sampling design. These data were used to estimate percentages of degraded vs. undegraded estuarine area from the perspective of sediment quality. Each year a sizable portion of the province (36% in 1994, 51 % in 1995) showed some evidence of either degraded benthic assemblages, contaminated sediments in excess of bioeffect guidelines, or significant sediment toxicity (based on Ampelisca abdita and Microtox® assays). However, co-occurrences of a degraded benthos and adverse exposure conditions (sediment contamination and/or toxicity) were much less extensive – 17% of the province in 1994 and 25% in 1995. Each year only four sites, representing 5% of the province in 1994 and 8% in 1995, had degraded infauna accompanied by both sediment contamination and toxicity, suggesting that strong contaminant-induced effects on the benthos (based on such combined weight-of-evidence) were limited to a fairly small percentage of estuarine area province-wide. PCBs and pesticides (lindane, dieldrin, DDT and derivatives) were the most dominant contaminants over the two-year period. The broad-scale sampling design of EMAP was not intended to support detailed characterizations of potential pollutant impacts within individual estuaries. Thus, some estuaries classified as undegraded may include additional degraded portions outside the immediate vicinity of randomly sampled sites. Such localized impacts (not accounted for in the above estimates) were detected in this study at additional nonrandom supplemental sites near potential contaminant sources. 相似文献
170.