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131.
Thomas E. Croley Carol L. Luukkonen 《Journal of the American Water Resources Association》2003,39(1):149-163
ABSTRACT: Computer simulations involving general circulation models, a hydrologic modeling system, and a ground water flow model indicate potential impacts of selected climate change projections on ground water levels in the Lansing, Michigan, area. General circulation models developed by the Canadian Climate Centre and the Hadley Centre generated meteorology estimates for 1961 through 1990 (as a reference condition) and for the 20 years centered on 2030 (as a changed climate condition). Using these meteorology estimates, the Great Lakes Environmental Research Laboratory's hydrologic modeling system produced corresponding period streamflow simulations. Ground water recharge was estimated from the streamflow simulations and from variables derived from the general circulation models. The U.S. Geological Survey developed a numerical ground water flow model of the Saginaw and glacial aquifers in the Tri‐County region surrounding Lansing, Michigan. Model simulations, using the ground water recharge estimates, indicate changes in ground water levels. Within the Lansing area, simulated ground water levels in the Saginaw aquifer declined under the Canadian predictions and increased under the Hadley. 相似文献
132.
133.
134.
Carol A. Bloomgarden 《Environmental management》1995,19(5):641-648
Anthropogenic climate climate change presents a unique challenge for endangered species policy and an opportunity for policy
makers to develop a more predictive and robust approach to preserving the nation's biological resources. Biological and ecological
reactions to shifting climate conditions and the potential feedbacks and synergistic effects of such changes may threaten
the well-being of many species, particularly of those already in jeopardy of extinction. The United States Endangered Species
Act of 1973 will fail to keep pace with increasing numbers of species needing protection as long as it remains focused on
protecting species individually. The actmust not be abandoned, however; it holds tremendous promise for preserving biological diversity through a more proactive, anticipatory
perspective. The current Endangered Species Act should be reinforced and improved by better integration of scientific expertise
into habitat and community preservation listing decisions and recovery plan devlopment. Given the uncertainties surrounding
long-term environmental consequences of human activities and resource use, a longer-term perspective must be integrated into
all efforts to protect our biotic resources.
Under appointment from the Graduate Fellowships for Global Change administered by the Oak Ridge Institute for Science and
Ecducation for the US Department of Energy. 相似文献
135.
Quality control is a crucial aspect of database management, particularly for physicochemical parameters that are widely used
in modeling environmental fate processes. Complete rechecking of original studies to verify environmental fate parameters
is time consuming and difficult. This paper evaluates an alternative, more efficient approach to identifying database errors.
The approach focuses verification efforts on a targeted subset of entries by making use of the relationship between water
solubility (S) and soil organic carbon partition coefficient (K
oc
). Two regression equations, one selected from the literature and one calculated from entries in the database, were used to
evaluate the reasonableness of (S, K
oc
) pairs among control compared to the targeted outlier group from a total of 59 pesticides. Our hypothesis was that (S, K
oc
) pairs that lay far from the regression line were more likely to be in error than those that fit the regression. Database
values were checked against original studies.
Identified errors in the database included coding mistakes, miscalculations, and incorrect chemical identification codes.
The error rate in outlier (S, K
oc
) pairs was about twice that of pairs that conformed to the regression equation; however, the error rate differential was
probably not large enough to justify the use of this quality control method. Through our close scrutiny of database entries
we were able to identify administrative practices that led to mistakes in the data base. Resolution of these problems will
significantly decrease the number of future mistakes. 相似文献
136.
137.
This study unveils causes of accidents in repair, maintenance, alteration and addition (RMAA) work. RMAA work is playing an increasingly important role in developed societies, including Hong Kong. Safety problems associated with RMAA work in Hong Kong has reached an alarming level. In view of rapid expansion of the RMAA sector and rising proportion of accidents in the construction industry, there is a pressing need to investigate causes of RMAA accidents. Structured interviews were conducted with RMAA contractors to explore causes of accidents in the RMAA sector. A two-round Delphi method with 13 safety experts was subsequently employed to verify the interview findings and rank the relative degree of importance for various causes of accidents. Accidents happen in RMAA work due to intersection of reasons. One of the root causes of accidents in RMAA works is low safety awareness of RMAA workers; however, wider organizational and industrial factors are not negligible. This study sheds light on why accidents happen in the RMAA sector. Only when the factors leading to accidents are identified can effective measures be made. 相似文献
138.
Keith E. Schilling Carol A. Thompson 《Journal of the American Water Resources Association》2000,36(5):1101-1114
ABSTRACT: Land use and surface water data for nitrogen and pesticides (1995 to 1997) are reported for the Walnut Creek Watershed Monitoring Project, Jasper County Iowa. The Walnut Creek project was established in 1995 as a nonpoint source monitoring program in relation to watershed habitat restoration and agricultural management changes implemented at the Neal Smith National Wildlife Refuge by the U.S. Fish and Wildlife Service. The monitoring project utilizes a paired‐watershed approach (Walnut and Squaw creeks) as well as upstream/downstream comparisons on Walnut for analysis and tracking of trends. From 1992 to 1997, 13.4 percent of the watershed was converted from row crop to native prairie in the Walnut Creek watershed. Including another 6 percent of watershed farmed on a cash‐rent basis, land use changes have been implemented on 19.4 percent of the watershed by the USFWS. Nitrogen and pesticide applications were reduced an estimated 18 percent and 28 percent in the watershed from land use changes. Atrazine was detected most often in surface water with frequencies of detection ranging from 76–86 percent. No significant differences were noted in atrazine concentrations between Walnut and Squaw Creek. Nitrate‐N concentrations measured in both watersheds were similar; both basins showed a similar pattern of detection and an overall reduction in nitrate‐N concentrations from upstream to downstream monitoring sites. Water quality improvements are suggested by nitrate‐N and chloride ratios less than one in the Walnut Creek watershed and low nitrate‐N concentrations measured in the subbasin of Walnut Creek containing the greatest amount of land use changes. Atrazine and nitrate‐N concentrations from the lower portion of the Walnut Creek watershed (including the prairie restoration area) may be decreasing in relation to the upstream untreated component of the watershed. The frequencies of pesticide detections and mean nitrate‐N concentrations appear related to the percentage of row crop in the basins and subbasins. Although some results are encouraging, definitive water quality improvements have not been observed during the first three years of monitoring. Possible reasons include: (1) more time is needed to adequately detect changes; (2) the size of the watershed is too large to detect improvements; (3) land use changes are not located in the area of the watershed where they would have greatest effect; or (4) water quality improvements have occurred but have been missed by the project monitoring design. Longer‐term monitoring will allow better evaluation of the impact of restoration activities on water quality. 相似文献
139.
Carol A Johnston Dana M Ghioca Mirela Tulbure Barbara L Bedford Michael Bourdaghs Christin B Frieswyk Lynn Vaccaro Joy B Zedler 《Ecological applications》2008,18(4):983-1001
Emergent plants can be suitable indicators of anthropogenic stress in coastal wetlands if their responses to natural environmental variation can be parsed from their responses to human activities in and around wetlands. We used hierarchical partitioning to evaluate the independent influence of geomorphology, geography, and anthropogenic stress on common wetland plants of the U.S. Great Lakes coast and developed multi-taxa models indicating wetland condition. A seven-taxon model predicted condition relative to watershed-derived anthropogenic stress, and a four-taxon model predicted condition relative to within-wetland anthropogenic stressors that modified hydrology. The Great Lake on which the wetlands occurred explained an average of about half the variation in species cover, and subdividing the data by lake allowed us to remove that source of variation. We developed lake-specific multi-taxa models for all of the Great Lakes except Lake Ontario, which had no plant species with significant independent effects of anthropogenic stress. Plant responses were both positive (increasing cover with stress) and negative (decreasing cover with stress), and plant taxa incorporated into the lake-specific models differed by Great Lake. The resulting models require information on only a few taxa, rather than all plant species within a wetland, making them easier to implement than existing indicators. 相似文献
140.
Woody plants in grasslands: post-encroachment stand dynamics 总被引:3,自引:0,他引:3
Dawn M Browning Steven R Archer Gregory P Asner Mitchel P McClaran Carol A Wessman 《Ecological applications》2008,18(4):928-944
Woody plant abundance is widely recognized to have increased in savannas and grasslands worldwide. The lack of information on the rates, dynamics, and extent of increases in shrub abundance is a major source of uncertainty in assessing how this vegetation change has influenced biogeochemical cycles. Projecting future consequences of woody cover change on ecosystem function will require knowledge of where shrub cover in present-day stands lies relative to the realizable maximum for a given soil type within a bioclimatic region. We used time-series aerial photography (1936, 1966, and 1996) and field studies to quantify cover and biomass of velvet mesquite (Prosopis velutina Woot.) following its proliferation in a semidesert grassland of Arizona. Mapping of individual shrubs indicated an encroachment phase characterized by high rates of bare patch colonization. Upon entering a stabilization phase, shrub cover increases associated with recruitment and canopy expansion were largely offset by contractions in canopy area of other shrub patches. Instances of shrub disappearance coincided with a period of below-average rainfall (1936-1966). Overall, shrub cover (mean +/- SE) on sandy uplands with few and widely scattered shrubs in 1902 was dynamically stable over the 1936-1996 period averaging approximately 35% +/- 5%. Shrub cover on clayey uplands in 1936 was 17% +/- 2% but subsequently increased twofold to levels comparable to those on sandy uplands by 1966 (36% +/- 7%). Cover on both soils then decreased slightly between 1966 and 1996 to 28% +/- 3%. Thus, soil properties influenced the rate at which landscapes reached a dynamic equilibrium, but not the apparent endpoint. Although sandy and clayey landscapes appear to have stabilized at comparable levels of cover, shrub biomass was 1.4 times greater on clayey soils. Declines in shrub cover between 1966 and 1996 were accompanied by a shift to smaller patch sizes on both sandy and clayey landscapes. Dynamics observed during the stabilization phase suggest that density-dependent regulation may be in play. If woody cover has transitioned from directional increases to a dynamic equilibrium, biomass projections will require monitoring and modeling patch dynamics and stand structure rather than simply changes in total cover. 相似文献