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41.
Expansion of the distribution of exotic rainbow trout is thought to be a leading cause for the decline of native brook trout since the 1930s in Great Smoky Mountains National Park, USA. An experimental rehabilitation project was conducted from 1976 to 1981 using backpack electrofish shockers on four remnant brook trout populations sympatric with rainbow trout. The objectives were to evaluate the effectiveness of the technique to remove the exotic rainbow trout, to determine the population responses by native brook trout, and to evaluate the usefulness of the technique for trout management in the park.Rainbow trout populations were greatly reduced in density after up to six years of electrofishing, but were not eradicated. Rainbow trout recruitment, however, was essentially eliminated. Brook trout populations responded by increasing in density (including young-of-the-year), but rates of recovery differed among streams. The maximum observed densities ir each stream occurred at the end of the project.The findings suggest that electrofishing had a major negative impact on the exotic species, which was followed by positive responses from the native species in the second and third order study streams. The technique would probably be less effective in larger (fourth-order) park streams, but as an eradication tool the technique may have its highest potential in small first order streams. Nonetheless, the technique appears useful for population control without causing undue impacts on native aquatic species, although it is labor intensive, and capture efficiency is greatly influenced by fish size and stream morphology. To completely remove the exotic fish from selected streams, different technologies will have to be explored and developed. 相似文献
42.
Large-scale constructed wetlands for nutrient removal from stormwater runoff: An everglades restoration project 总被引:14,自引:0,他引:14
Mariano Guardo Larry Fink Thomas D. Fontaine Susan Newman Michael Chimney Ronald Bearzotti Gary Goforth 《Environmental management》1995,19(6):879-889
The South Florida Water Management District (SFWMD) constructed a wetland south of Lake Okeechobee to begin the process of
removing nutrients (especially phosphorus) from agricultural stormwater runoff entering the Everglades. The project, called
the Everglades Nutrient Removal (ENR) project, is a prototype for larger, similarly constructed wetlands that the SFWMD will
build as part of the Everglades restoration program. This innovative project is believed to be one of the largest agricultural
stormwater cleanup projects in the United States, if not in the world. This publication describes the ENR project's design,
construction, and proposed operation, as well as the proposed research program to be implemented over the next few years. 相似文献
43.
Gregory M. Jue Sally Ann Shumaker Gary W. Evans 《Journal of environmental psychology》1984,4(4):337-345
In the present study we examined (1) community opinion of airport noise-abating alternatives and (2) the influence of perceived control on attitudes concerning noise-abatement policies and annoyance toward aircraft noise. We proposed that residents who perceive themselves as having little control over aircraft noise exposure would express higher levels of annoyance than residents who believe they have some degree of control. Furthermore, residents with low levels of perceived control would be less favorable toward proposed noise-abatement alternatives. Survey results collected from 239 households within the 65 CNEL contour of a community airport in Southern California support these hypotheses. Findings indicate strong public support for noise abatement and strong opposition to land-use alternatives. In addition, residents' perceptions of control in the airport planning and management process are significantly related to their annoyance with noise and their opinions about noise management policies. 相似文献
44.
45.
Gary B. Kappesser 《Journal of the American Water Resources Association》2002,38(4):1069-1081
ABSTRACT: Riffles in moderately entrenched stream reaches with gradients of 2 percent to 4 percent that have received excessive sediment from upstream have a distinctly different and higher proportion of smaller mobile particles than riffles in systems that are in dynamic equilibrium. The mobile fraction on the riffle can be estimated by comparing the relative abundance of various particle sizes present on the riffle with the dominant large particles on an adjacent bar. Riffle particles smaller than the dominant large particles on the bar are interpreted as mobile. The mobile percentile of particles on the riffle is termed “Riffle Stability Index” (RSI) and provides a useful estimate of the degree of increased sediment supply to riffles in mountain streams. The RSI addresses situations in which increases in gravel bedload from headwaters activities is depositing material on riffles and filling pools, and it reflects qualitative differences between reference and managed watersheds. The RSI correlates well with other measures of stream channel physical condition, such as V and the results of fish habitat surveys. Thus, it can be used as an indicator of stream reach and watershed condition and also of aquatic habitat quality. 相似文献
46.
David M. Wolock Gregory J. McCabe Gary D. Tasker Marshall E. Moss 《Journal of the American Water Resources Association》1993,29(3):475-486
ABSTRACT: The effects of potential climate change on water resources in the Delaware River basin were determined. The study focused on two important water-resource components in the basin: (1) storage in the reservoirs that supply New York City, and (2) the position of the salt front in the Delaware River estuary. Current reservoir operating procedures provide for releases from the New York City reservoirs to maintain the position of the salt front in the estuary downstream from freshwater intakes and ground-water recharge zones in the Philadelphia metropolitan area. A hydrologic model of the basin was developed to simulate changes in New York City reservoir storage and the position of the salt front in the Delaware River estuary given changes in temperature and precipitation. Results of simulations indicated that storage depletion in the New York City reservoirs is a more likely effect of changes in temperature and precipitation than is the upstream movement of the salt front in the Delaware River estuary. In contrast, the results indicated that a rise in sea level would have a greater effect on movement of the salt front than on storage in the New York City reservoirs. The model simulations also projected that, by decreasing current mandated reservoir releases, a balance can be reached wherein the negative effects of climate change on storage in the New York City reservoirs and the position of the salt front in the Delaware River estuary are minimized. Finally, the results indicated that natural variability in climate is of such magnitude that its effects on water resources could overwhelm the effects of long-term trends in precipitation and temperature. 相似文献
47.
48.
Dwayne H. Fink Gary W. Frasier Lloyd E. Myers 《Journal of the American Water Resources Association》1979,15(3):861-873
ABSTRACT: Yearly runoff efficiencies (total runoff/total precipitation), threshold retentions (precipitation needed to initiate runoff), and runoff-efficiencies-after-thresholds were determined for several water-harvesting catchment treatments at the Granite Reef test site. This information was found to be useful for showing (1) overall performance of catchments with time; (2) the distribution of the precipitation among runoff, surface retention, and infiltration; (3) why, how, and when certain treatments weathered and failed; (4) when to repair treatments; and (5) how to design catchments (size, site preparation, material selection, etc.). New impermeable membranes with smooth surfaces yielded nearly 100% of the precipitation. An asphalt-fiberglass treatment continues this high efficiency after 10 years of weathering – polyethylene after 8; efficiency of butyl sheeting was high initially but decreased rapidly after 9 years weathering. A standard roofing treatment retained up to 30% of the precipitation in the gravel covering. A concrete catchment lost as much as 50% of the total precipitation through micropores and surface cracks. Silicone treatments rapidly lost repellancy and efficiency, while paraffin treatments have weathered 5 years with little loss of efficiency. 相似文献
49.
Gary L. Larson 《Environmental management》1980,4(2):105-110
Since the presentation of the Leopold Report (Leopold et al. 1963) to the United States Secretary of the Interior, recommendations in the document for managing natural park resources on the ecosystem level have been included in the management policies of the National Park Service. In many instances, however, management programs have continued to focus on individual resource problems, without apparent concern for the ecological consequences on ecosystems. Without knowledge of the interrelationships of ecosystem components, solving one problem may result in other resource problems. Graphic approaches are presented as potential tools to view these complex interrelationships relative to the needs of the resource manager. Interpreting the dynamics of aquatic systems is emphasized. 相似文献
50.
Gordon C. Jacoby Gary D. Weatherford Judith W. Wegner 《Journal of the American Water Resources Association》1976,12(5):973-985
ABSTRACT: Law and hydrology are inextricably woven together in the pattern of water resource development in the west. The former attempts to allocate a limited and valuable resource as the latter tries to define the limits of the resource. In the past an inadequate data base has made hydrologic estimates difficult and political factors have pushed the law into possibly conflicting commitments in the Colorado River Basin. Through the use of tree-ring research, hydrologists have produced a more definitive data base and placed water allocations such as the Colorado River Compact of 1922 in a clearer long-term perspective. This data base leads to the conclusion that the surface-water supply is about 13.5 million acre-feet per year. This hydrologic limit must be apportioned within an existing legal framework - the “Law of the River.” As development approaches the resource limit in the Upper Colorado River Basin, lawyers and hydrologists must act in concert toward the equitable solution of allocation and reallocation problems. 相似文献