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291.
Charles R. Fellows Patrick L. Brezonik 《Journal of the American Water Resources Association》1980,16(4):635-641
ABSTRACT: Direct measurements indicate that subsurface seepage in the littoral zone contributed 17.5 and 2.0 percent of the total hydraulic inputs, respectively, to Lakes Conway and Apopka, Florida. Two variations of seepage measuring devices were evaluated and gave relative standard deviations of 7 and 24 percent. Measurement inaccuracies were minimized by using large diameter (0.9 cm ID) plastic tubing. For a given transect perpendicular to shore, flow patterns were reproducible over time. Seepage flows ranged from 0 to 112 1/m2-day and most were between 4 and 30 1/m2-day. The detection limit was about 0.2 1/m2-day for a one-hour collection period. Seepage occured primarily within 30 m of shore and generally decreased exponentially with distance from shore. The shape of the bottom profile influenced flow patterns; lake bottoms with steeper slopes had higher flows that were compressed within a narrower zone. After a short-term rain event at Lake Conway, seepage flows increased rapidly to 2.4 times the prerain flow for 1 h and decreased to near background within about 6 h. 相似文献
292.
Kennith E. Foster Robert A. Schowengerdt Charles E. Glass 《Journal of the American Water Resources Association》1980,16(5):934-937
ABSTRACT: Water supplies in Arizona are becoming increasingly limited because municipal, industrial, and agricultural consumption depletes ground water reserves by three million acre-feet annually. Additional demands are being created by electric power generation, particularly in northeastern Arizona where ground water pumpage is expected to escalate by sixfold during the next 10 years. The results of a study to determine the ease and feasibility of using satellite imagery as a tool in exploring for new sources of ground water are reported. Lineaments detected on Landsat images of two sites were mapped and correlated with well data in the two study areas by means of well centered grid model. The correlations developed between lineament density and water well data in the two study sites support the hypothesis that a relationship exists between regional geologic structure and the presence of ground water. 相似文献
293.
294.
Charles Brendecke Leonard Ortolano 《Journal of the American Water Resources Association》1981,17(2):248-254
ABSTRACT: Survey data from samples of two types of Corps of Engineers planning studies have been collected. The nature of significant environmental issues affecting the studies was ascertained. Information concerning District administrative practices and communication patterns and extraorganizational coordination procedures was also obtained. Statistical analysis examined the relationships between these practices and procedures and the consideration given environmental issues in plan formulation and modification decisions. Environmental issues receive greater consideration in plan formulation decisions where District policies encourage interdisciplinary planning and direct communication between planners and environmental interests. Plan modification decisions reflect environmental considerations to a greater degree where significant controversy exists and where reviewing agencies actively pursue environmental issues. 相似文献
295.
Charles V. Moore 《Journal of the American Water Resources Association》1972,8(4):802-812
ABSTRACT. Salinization and water logging have been the nemesis of irrigated agriculture societies since Babylonian times. Low quality water substitutes for high quality water for irrigation at an increasing rate up to the limits of the soil's ability to transmit the additional water and remove excess salts from the root zone. Soil transmissibility can be increased by additional investment in drainage ditches and underground tile. Low valued-high salt tolerant crops can be substituted for higher valued-salt sensitive crops to maintain production in areas served by irrigation water sources of deteriorating quality. Thus physical factors specify the necessary conditions for survival of an irrigated agriculture. The sufficient conditions for survival must be in terms of a positive net income in each subplanning period discounted to its present value. 相似文献
296.
Reynolds SD Blanchard CL Ziman SD 《Journal of the Air & Waste Management Association (1995)》2004,54(11):1452-1470
Analyses of ozone (O3) measurements in conjunction with photochemical modeling were used to assess the feasibility of attaining the federal 8-hr O3 standard in the eastern United States. Various combinations of volatile organic compound (VOC) and oxides of nitrogen (NOx) emission reductions were effective in lowering modeled peak 1-hr O3 concentrations. VOC emissions reductions alone had only a modest impact on modeled peak 8-hr O3 concentrations. Anthropogenic NOx emissions reductions of 46-86% of 1996 base case values were needed to reach the level of the 8-hr standard in some areas. As NOx emissions are reduced, O3 production efficiency increases, which accounts for the less than proportional response of calculated 8-hr O3 levels. Such increases in O3 production efficiency also were noted in previous modeling work for central California. O3 production in some urban core areas, such as New York City and Chicago, IL, was found to be VOC-limited. In these areas, moderate NOx emissions reductions may be accompanied by increases in peak 8-hr O3 levels. The findings help to explain differences in historical trends in 1- and 8-hr O3 levels and have serious implications for the feasibility of attaining the 8-hr O3 standard in several areas of the eastern United States. 相似文献
297.
States use a variety of approaches to encourage landowners and loggers to apply ecologically-sustainable timber harvesting practices, the latter generically referred to as timber harvesting guidelines. A survey of 37 state forestry agency administrators in the eastern U.S. (defined as a contiguous region with the northwest and southwest borders being North Dakota and Texas, respectively) was conducted in 2000 to assess the extent and nature of state guideline programs and the various methods by which states encourage their use. The study found states in the eastern U.S. use a variety of policy tools to promote guideline use, with certain policy tools more common for certain target audiences (e.g., loggers) as well as the types of resources (e.g., wildlife habitat) addressed by the guidelines. Eighty-three percent of the programs directed at encouraging forest landowners in the eastern U.S. to use the timber harvesting practices identified in their state guidebooks are technical assistance, educational, or cost-share programs. Technical assistance and education programs are the most common policy tools used to assist loggers in applying sustainable harvesting practices. Technical assistance and cost-share programs consistently rank among the most effective policy tools for encouraging loggers and landowners to apply the guidelines. Comparing the level of program investment to perceived benefits, assistance programs and education programs rank most efficient landowner programs, whereas premium prices for products and preferential access to contracts are the two most efficient programs directed at loggers. The paper concludes with an assessment of emerging trends and additional information needs associated with encouraging the application of sustainable timber harvesting practices. 相似文献
298.
Smith CN Goshawk JA Charles K McDonald P Leonard KS McCubbin D 《Journal of environmental radioactivity》2003,68(3):193-214
The predictions from MEAD, a model that simulates the transport of radionuclides in the marine environment, are presented for the Irish Sea. MEAD predictions for (137)Cs and Pu(alpha) are presented following discharges from BNFL Sellafield and the predictions compared to measured data from near the discharge location and further a field in the Irish Sea. The model performs well in most circumstances given the uncertainties involved in both modelling and data collection although some inconsistencies in the predictions are found. MEAD is also compared to other models of radionuclide transport in the Irish Sea. 相似文献
299.
Charles F. Leaf 《Journal of the American Water Resources Association》1998,34(4):865-876
ABSTRACT: An accounting procedure is developed which determines a flow regime that is capable of transporting an amount of bedload sediment necessary to ensure channel stability downstream. The method allows for sediment buildup in the channel within geomorphic threshold limits during low flow periods. During periods of high runoff, enough water is bypassed to transport the stored sediment. The procedure utilizes only those flows of sufficient magnitude to maintain channel stability over the long run (25–50+ years). An example is presented which determines the volume of water and frequency of release for channel maintenance purposes downstream from a hypothetical water diversion project. Of some 1,200,000 acre feet generated during a 59-year period, 86,500 acre feet was required for channel maintenance flows. Bypass flows were not required each year, but only during those years when average daily flow reached bankfull or greater. Such releases were made on 202 of the 411 days when average flows either equalled or exceeded bankfull discharge. 相似文献
300.
Charles H. Eccleston 《环境质量管理》1998,7(3):9-17
It is vital that federal managers consider new approaches for enhancing environmental protection while reducing redundancies and cost. Faced with increasing environmental issues, compliance requirements, competing resources, and tightened budget constraints, agencies must seek innovative approaches for doing more with less. The diverse array of confusing and sometimes inappropriate or conflicting regulatory requirements compounds compliance complexities and increases the need to seek resourceful solutions. At a time when NEPA is coming under closer congressional scrutiny, an integrated NEPA/EMS paradigm provides a key for increasing the effectiveness and uniformity of implementing NEPA at the early planning stage, while reducing cost, delays, and redundancies. Effectively integrated, NEPA satisfies one of the five, and perhaps most important, principles of an EMS-environmental planning. NEPA's regulatory requirements not only are consistent with the objective of an EMS, but actually enhance the effectiveness of an EMS. An integrated approach provides the added benefit of increased environmental coordination and heightened communications that translates into further cost reduction and fewer delays. The strategy described in this article is designed to balance the rigors of an international standard with the need to efficiently implement an integrated NEPA/EMS system, given a diverse set of challenging circumstances and constraints. 相似文献