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121.
Trevor C. Hughes Ronald V. Canfield 《Journal of the American Water Resources Association》1977,13(3):479-488
ABSTRACT: Many rural areas of the United States still have no public domestic water systems. Typical land use patterns in these areas may require 1/2 mile or more of pipe per farm connection. Public systems serving these areas are economically feasible only if realistic short-term peak demand standards are available for their design. The lack of reliable data upon which to establish such criteria has resulted in a large variation in criteria among state and federal agencies involved in financing and in approving construction of these systems. During the summer of 1975 three distribution laterals of a rural system in Utah were master metered and instantaneous peak flows were recorded for 4 months. The metered lines served 4, 12, and 22 farm houses each. The frequency distribution of peak flows has been analyzed and compared with that developed during similar research in Mississippi and with the existing design standards of the Farmers Home Administration and the State of Utah. 相似文献
122.
F. Harvey Dove Peter J. Schreuder 《Journal of the American Water Resources Association》1979,15(2):326-336
ABSTRACT: A visual selection technique can be utilized to locate potential well field sites prior to on-site testing. The technique is based upon an understanding of the regional hydrology and an appreciation for development goals such as the identification of high-yield and low-impact locations. Although the uniqueness of Pasco, Pinellas, and Hillsborough Counties in Western Florida has been incorporated into the current application, the methodology, with modifications, is transferable to other geographic regions. Overlays of each criterion used in site selection are combined to form a regional composite showing favorable site locations and further serve a useful communications role as visual aids during public presentation. Implications of direct and indirect cost savings to the public are obtained when the methodology is applied to the location of municipal well fields. 相似文献
123.
关于中国西南石漠化的若干问题 总被引:31,自引:1,他引:30
石漠化是西南岩溶山地脆弱生态系统发生的土地退化。根据已有的经验和研究成果,深入探讨了中国西南岩溶山地喀斯特石漠化的科学内涵、成因、发展过程、评价指标及防治机理等。土壤和植被是岩溶环境中最为敏感的自然环境要素,可能是石漠化过程的主要自然成因,而以土地利用为表现形式的强烈人类活动为驱动力;石漠化的发生发展过程即人为过程→生物学过程→加速的地学过程。石漠与石漠化,二者属于完全不同的范畴,不同空间尺度的石漠化评价应有不同的评价指标、标准和石漠化生态基准的多样性,以便为石漠化的演化研究及生态重建起一定的参考作用。鉴于石漠化现象在我国现实中存在的客观性、在理论概念上的模糊性及在生态治理中的急迫性,有必要加强石漠化在不同时空尺度下的驱动机制研究,特别是人类驱动力的研究,加强原生岩溶生态系统和受损岩溶生态系统运行规律的研究。 相似文献
124.
Main R. Hutcheson 《Journal of the American Water Resources Association》1998,34(5):1025-1033
ABSTRACT: Acute criteria are assigned to the fish and wildlife propagation beneficial use in Oklahoma's water quality standards. Dye studies are analyzed to show that these criteria can be implemented through acute regulatory mixing zones. Acute regulatory mixing zones may be defined as areas in receiving streams where acute numerical criteria may be exceeded without causing acute toxicity. Acute regulatory mixing zones are used to obtain acute waste load allocations. If effluent loading does not exceed acute waste load allocation, acute criteria exceedance is confined to the acute regulatory mixing zone and there is no acute toxicity in the receiving stream. Waste load allocations for acute and chronic criteria are compared to determine which is appropriate to develop permit limits for the dye studies. 相似文献
125.
Gerald T. Ankley Nelson A. Thomas Dominic M. Di Toro David J. Hansen John D. Mahony Walter J. Berry Richard C. Swartz Robert A. Hoke A. Wayne Garrison Herbert E. Allen Christopher S. Zarba 《Environmental management》1994,18(3):331-337
Due to anthropogenic inputs, elevated concentrations of metals frequently occur in aquatic sediments. In order to make defensible
estimates of the potential risk of metals in sediments and/or develop sediment quality criteria for metals, it is essential
to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates
indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavailability of metals in
test sediments. Many factors may influence pore water concentrations of metals; however, in anaerobic sediments a key phase
controlling partitioning of several cationic metals (cadmium, nickel, lead, zinc, copper) into pore water is acid volatile
sulfide (AVS). In this paper, we present an overview of the technical basis for predicting bioavailability of cationic metals
to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Included are discussions of the
advantages and limitations of metal bioavailability predictions based on these parameters, relative both to site-specific
assessments and the development of sediment quality criteria. 相似文献
126.
Helen Briassoulis 《Environmental management》1995,19(2):297-311
Environmental criteria are increasingly being employed in industrial facility siting, usually in multicriteria decision contexts,
together with technical, socioeconomic and other considerations. This paper analyzes the criteria that have appeared in the
published literature with the aim to offer guidance for their selection in a particular facility location problem. A number
of alternative classification schemes are presented, first based on the most prevalent classification dimensions which are:
the economy-environment relationship, purpose of the criterion, complexity, spatial and temporal scale, and level of measurement.
The major scheme adopted draws from the economy-environment relationship and assigns environmental critera to one of seven
categories: general characterizations of the environment, characteristics of individual environmental components, measures
of the magnitude and intensity of the activity, measures of the nature and volume of wastes which are produced, characteristics
of impacts on separate environmental media and receptors, general characterizations of environmental quality, and impacts
on humans. Within each of these categories the criteria are analyzed in terms of the other classification dimensions. Common
characteristics among the various criteria as well as future trends in their development are identified. This paper also discusses
the most important factors conditioning the choice of criteria in a particular facility siting context and outlines a systematic
procedure for their selection in real-world applications. 相似文献
127.
John Cairns 《Journal of the American Water Resources Association》1986,22(5):841-842
ABSTRACT: Direct measurement of response thresholds of complex biological systems to toxic chemicals is now possible using microcosms and other simulation techniques. Extrapolation to no-observable response using application factors and data from single species toxicity tests is less precise than direct measurements. 相似文献
128.
Spatial based compromise programming for multiple criteria decision making in land use planning 总被引:1,自引:0,他引:1
Sumbangan Baja David M. Chapman Deirdre Dragovich 《Environmental Modeling and Assessment》2007,12(3):171-184
Today, competing land use is continuing to occur in many developed regions. In the Agricultural Development Zone of Western
Sydney Region, which is characterised by complex landscape patterns, land use competition is widespread. From a land use planning
perspective, identification of suitable locations for a given type of land use is necessary for decision makers to formulate
land use alternatives in different locations, based on existing land potential and constraints. For such a region, use of
a simple method that implements a categorical system and considers only inherent land characteristics in the analysis is often
inadequate to arrive at an optimal spatial decision. The primary aim of this paper is to develop spatial modelling procedures
for agricultural land suitability analysis using compromise programming (CoPr) and fuzzy set approach within a geographical
information systems (GIS) environment. Five main sets of spatial data for use as decision criteria were developed by using
fuzzy set methodology: a land suitability index (LSI) for maximising the land productivity objective; an erosion tolerance
index (ETI) for minimising the erosion risk objective; a runoff curve number (CN) for maximising the water discharge regulation
objective; an accessibility (RP) measure for maximising the land accessibility objective; and the proximity to water body
(WP) for minimising the water pollution objective. An L
p
-metric was used in the analysis utilising different strategies with representative indices ranging from a situation where
full tradeoff among criteria occurs to a noncompensatory condition. Different weighting combinations were also applied, and decision analysis was carried out by using values ranging
from 0 to 1.0, where 1.0 is considered as an ideal point. The CoPr model demonstrated in this paper yielded a promising result,
as several different techniques of sensitivity analysis show reasonably good results. Likewise, an overlay of that result
with the present land use/land cover indicates a good corresponding spatial matching between existing land use (orchard and
cultivated land), and the cells (land parcels) classified as the best in CoPr. The results are amenable to various map display
techniques, either using continuous values or by defining different cut off points in the data space within a raster GIS environment. 相似文献
129.
Surveys were completed on Tutuila Island, American Samoa, to characterize reef development and assess the impacts of non-point source pollution on adjacent coral reefs at six sites. Multivariate analyses of benthic and coral community data found similar modern reef development at three locations; Aoa, Alofau, and Leone. These sites are situated in isolated bays with gentle sloping foundations. Aoa reefs had the highest estimates of crustose coralline algae cover and coral species richness, while Leone and Alofau showed high abundances of macroalgae and Porites corals. Aoa has the largest reef flat between watershed discharge and the reef slope, and the lowest human population density. Masefau and Fagaalu have a different geomorphology consisting of cemented staghorn coral fragments and steep slopes, however, benthic and coral communities were not similar. Benthic data suggest Fagaalu is heavily impacted compared with all other sites. Reef communities were assessed as bio-criteria indicators for waterbody health, using the EPA aquatic life use support designations of (1) fully supportive, (2) partially supportive, and (3) non-supportive for aquatic life. All sites resulted in a partially supportive ranking except Fagaalu, which was non-supportive. The results of this rapid assessment based upon relative benthic community measures are less desirable than long-term dataset analyses from monitoring programs, however it fills an important role for regulatory agencies required to report annual waterbody assessments. Future monitoring sites should be established to increase the number of replicates within each geological and physical setting to allow for meaningful comparisons along a gradient of hypothesized pollution levels. 相似文献
130.
基于ABAQUS的强度折减有限元法边坡稳定性分析 总被引:6,自引:0,他引:6
将强度折减有限元法与ABAQU S软件相结合,充分利用ABAQU S软件强大的后处理功能,动态显示广义塑性应变和塑性区的开展情况,以此对边坡稳定性进行判定。在ABAQU S软件的模拟计算中,通过不断调整强度折减系数F的大小,改变土体的强度指标c、值,得到不同折减系数下边坡中广义塑性应变的发展情况;当塑性区趋于贯通,且广义塑性应变和位移发生突变时,则边坡处于破坏的临界状态,此时的折减系数就定义为边坡的最小稳定安全系数。通过天然直立边坡及开挖边坡的实例分析,表明该法可以较准确形象地预测边坡潜在滑裂面的位置及评价边坡的稳定性,在复杂条件下的基坑边坡稳定性分析中是简便实用的。 相似文献