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51.
Gilbert S. Nicolson Edwin E. Pyatt David H. Moreau 《Journal of the American Water Resources Association》1970,6(1):23-33
While reservoirs are constructed to regulate stream flows for several beneficial purposes including flood control, water supply, hydroelectric power, irrigation and low flow augmentation and to enhance water based recreation, they create problems of water quality that offer a new dimension to the task of efficient operation. Among other potential deleterious effects, thermal stratification in reservoirs inhibits mixing and causes a deterioration of dissolved oxygen levels in lower layers. Several investigators have examined the thermal properties of reservoirs and resultant effects upon dissolved oxygen and have suggested alternative schemes for alleviating detrimental effects (1,2,3,4,5). The objective of this paper is to outline a methodology for evaluating some of these alternatives in a river-reservoir system where downstream water quality control is one of several purposes to be served by the reservoir. 相似文献
52.
Roger L. Kaesler Edwin E. Herricks 《Journal of the American Water Resources Association》1979,15(4):1117-1125
ABSTRACT: Hierarchical diversity analysis of data on fish and aquatic insects showed that the component of diversity contributed by the species level was generally very small compared with the component at the generic level or with the total diversity. Very high rank correlations between generic diversity, in which genera were discriminated but not identified, and species diversity suggested that the purposes of environmental monitoring might best be served by working at the generic level rather than the species level. This is particularly true when an index of diversity is to be used as the major comparative and communicative tool. The savings of time and money could be appreciable. 相似文献
53.
A Multiscale Conceptual Framework for Integrated Ecogeomorphological Research to Support Stream Naturalization in the Agricultural Midwest 总被引:1,自引:0,他引:1
The complexity of fluvial systems necessitates interdisciplinary research in fluvial geomorphology and aquatic ecology to
develop a fundamental understanding of interconnections among biotic and abiotic aspects of these systems. Integrated knowledge
of this type is vital for environmental management of streams in human-dominated environments. A conceptual framework is presented
for integrating geomorphological and ecological research on streams in East Central Illinois, USA, a glaciated low-relief
agricultural landscape. The framework embodies a multiscale perspective in which a geomorphological conception of the fluvial
system is used to define a hierarchy of characteristic spatial scales for exploring important linkages between stream geomorphology
and aquatic ecology. The focus ecologically is on fish, because a rich body of historical information exists on fisheries
in East Central Illinois and because past work has suggested that availability of physical habitat is a major factor influencing
the community characteristics of fish in this human-altered environment. The hierarchy embodied in the framework includes
the network, link, planform, bar unit, bar element, and bedform/grain scales. Background knowledge from past research is drawn
upon to identify potential linkages between geomorphological and ecological conditions at each of these scales.
The conceptual framework is useful for guiding integrated ecogeomorphological research at specific scales and across different
scales. It also is helpful for illustrating how widespread human modification of streams has catastrophically altered the
scalar structure of fluvial systems in East Central Illinois. Knowledge emerging from the integrated research provides a basis
for environmental-management schemes directed toward stream naturalization. 相似文献
54.
Eppe G Van Cleuvenbergen R Smastuen Haug L Boulanger B Becher G De Pauw E 《Chemosphere》2008,71(2):379-387
Dioxin analysis in food and feed can be characterized as an analytical application where very high accuracy is required at very low levels of contamination. Gas chromatography (GC) in combination with 13C-label isotope dilution (ID) high resolution mass spectrometry (HRMS) is the reference congener-specific technique characterized by pronounced selectivity, precision and trueness at parts-per-trillion (ppt) and sub-parts-per-trillion (sub-ppt) levels. The quality of the analytical data produced routinely by a laboratory should be adequate for its intended purpose, i.e., one will seek a compromise between the cost and time needed and the consequences of incorrect decisions due to erroneous results. The requirements for reproducibility are usually dependent on the analyte concentrations and have been expressed in various empirical functions. While Horwitz or modified functions are widely useful for many purposes, it would be difficult to expect these functions to cover every analytical problem. This study reports on precision characteristics achieved by the GC-ID-HRMS reference method for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in food and feed in two interlaboratory method-performance studies among expert laboratories with long-standing experience in this field. Striking linear functions in log scale between reproducibility standard deviation and congener's level over a concentration range of 10(-8)-10(-14)g per g fresh weight are observed. The data fit very well to a Horwitz-type function of the form sR=0.153c0.904, where sR and c are dimensionless mass ratios expressed in pg g(-1) on fresh weight, regardless of the nature of the toxic congeners, food and feed matrices, or sample preparation methods. We demonstrate that the proposed function is suitable for use as a fitness-for-purpose criterion for proficiency assessment in interlaboratory comparisons on dioxins and related compounds in food. 相似文献
55.
Sebastian Vicuna Edwin P. Maurer Brian Joyce John A. Dracup David Purkey 《Journal of the American Water Resources Association》2007,43(2):482-498
Abstract: Using the latest available General Circulation Model (GCM) results we present an assessment of climate change impacts on California hydrology and water resources. The approach considers the output of two GCMs, the PCM and the HadCM3, run under two different greenhouse gas (GHG) emission scenarios: the high emission A1fi and the low emission B1. The GCM output was statistically downscaled and used in the Variable Infiltration Capacity (VIC) macroscale distributed hydrologic model to derive inflows to major reservoirs in the California Central Valley. Historical inflows used as inputs to the water resources model CalSim II were modified to represent the climate change perturbed conditions for water supply deliveries, reliability, reservoir storage and changes to variables of environmental concern. Our results show greater negative impacts to California hydrology and water resources than previous assessments of climate change impacts in the region. These impacts, which translate into smaller streamflows, lower reservoir storage and decreased water supply deliveries and reliability, will be especially pronounced later in the 21st Century and south of the San Francisco bay Delta. The importance of considering how climate change impacts vary for different temporal, spatial, and institutional conditions in addition to the average impacts is also demonstrated. 相似文献
56.
Edwin D. Bailey 《Journal of the American Water Resources Association》1979,15(3):801-811
ABSTRACT: The Tucson area is totally dependent on ground water, which is in increasingly short supply due to excessive overdrafts. Tucson area waste water treatment plants discharge material quantities of secondary effluent downstream, which is lost to evapotranspiration and recharge of the ground water basin. The city and the four large mining companies who share the common Santa Cruz basin ground water, recognized the common water supply problem and agreed to fund a feasibility study for mining process use of the effluent to partly alleviate the overdraft of ground water. The study analyzed the projected waste water effluent resources, potential mining company demand for waste water effluent and possible interface of an effluent delivery facility with the proposed Central Arizona Project. The effluent resources were analyzed with respect to potential demand. An optimum alignment was selected. An optimum system was detailed through design schematics, amortized cost and finance requirements, and an implementation schedule. It was concluded that a waste water effluent delivery facility could be implemented which would utilize reclaimed effluent in quantities approximating 35 percent of basin overdraft and which would provide revenue for full cost recovery over a 20 year operation period. The mining companies are studying the internal economic impacts of the project. 相似文献
57.
58.
Woodard KR French EC Sweat LA Graetz DA Sollenberger LE Macoon B Portier KM Wade BL Rymph SJ Prine GM Van Horn HH 《Journal of environmental quality》2002,31(6):1980-1992
Florida dairies need year-round forage systems that prevent loss of N to ground water from waste effluent sprayfields. Our purpose was to quantify forage N removal and monitor nitrate N (NO3(-)-N) concentrations in soil water below the rooting zone for two forage systems during four 12-mo cycles (1996-2000). Soil in the sprayfield is an excessively drained Kershaw sand (thermic, uncoated Typic Quartzipsamment). Over four cycles, average loading rates of effluent N were 500, 690, and 910 kg ha(-1) per cycle. Nitrogen removed by the bermudagrass (Cynodon spp.)-rye (Secale cereale L.) system (BR) during the first three cycles was 465 kg ha(-1) per cycle for the low loading rate, 528 kg ha(-1) for the medium rate, and 585 kg ha(-1) for the high. For the corn (Zea mays L.)-forage sorghum [Sorghum bicolor (L.) Moench]-rye system (CSR), N removals were 320 kg ha(-1) per cycle for the low rate, 327 kg ha(-1) for the medium, and 378 kg ha(-1) for the high. The higher N removals for BR were attributed to higher N concentration in bermudagrass (18.1-24.2 g kg(-1)) than in corn and forage sorghum (10.3-14.7 g kg(-1)). Dry matter yield declined in the fourth cycle for bermudagrass but N removal continued to be higher for BR than CSR. The BR system was much more effective at preventing NO3(-)-N leaching. For CSR, NO3(-)-N levels in soil water (1.5 m below surface) increased steeply during the period between the harvest of one forage and canopy dosure of the next. Overall, the BR system was better than CSR at removing N from the soil and maintaining low NO3(-)-N concentrations below the rooting zone. 相似文献
59.
Zisheng Xing Charles P.-A. Bourque Fan-Rui Meng Roger M. Cox D. Edwin Swift Tianshan Zha Lien Chow 《Ecological modelling》2008
In this paper we present a simple hybrid gap-filling model (GFM) designed with a minimum number of parameters necessary to capture the ecological processes important for filling medium-to-large gaps in Flux data. As the model is process-based, the model has potential to be used in filling large gaps exhibiting a broad range of micro-meteorological and site conditions. The GFM performance was evaluated using “Punch hole” and extrapolation experiments based on data collected in west-central New Brunswick. These experiments indicated that the GFM is able to provide acceptable results (r2 > 0.80) when >500 data points are used in model parameterization. The GFM was shown to address daytime evolution of NEP reasonably well for a wide range of weather and site conditions. An analysis of residuals indicated that for the most part no obvious trends were evident; although a slight bias was detected in NEP with soil temperature. To explore the portability of the GFM across ecosystem types, a transcontinental validation was conducted using NEP and ancillary data from seven ecosystems along a north-south transect (i.e., temperature–moisture gradient) from northern Europe (Finland) to the Middle East (Israel). The GFM was shown to explain over 75% of the variability in NEP measured at most ecosystems, which strongly suggests that the GFM maybe successfully applied to forest ecosystems outside Canada. 相似文献
60.
Chinnamuthu Nandakumar Ganapathy Saravanan Chidambaram Malaiperumal Vikneswaran Varuvel Edwin Geo Raman Vallinayagam Boologarajan Poonguzhali Kannan Ashok 《Environmental science and pollution research international》2021,28(26):33866-33879
Environmental Science and Pollution Research - This study aims to enhance the turbulence of direct injection (DI) diesel engine by modifying the inlet manifold design with an inclined nozzle-like... 相似文献