STABILITY AND REACH LENGTH IN WATER SURFACE PROFILE DETERMINATION1

ABSTRACT: Extension of basic step methods of backwater computation to reaches of finite length is examined. Accuracies of commonly accepted hydraulic loss equations under particular water surface profile conditions are compared. Simulation of energy lines within a reach by parabolic curves is found to minimize error provided orientation of the axis of the parabola is selected in accordance with prevailing hydraulic conditions. Theoretical basis for an index reach length beyond which single-step computation from end to end of the reach must be in error is developed. Reduction of this reach length by suitable factors tailored to hydraulic conditions yields a mathematically defined allowable reach length for backwater computation. When reach length does not exceed this allowable reach length, no significant error may be detected. Automatic insertion of synthetic cross sections interpolated between surveyed cross sections when these are inadvertently spaced too far apart enables computation to proceed. This device is error-free for prismatic channls but may introduce error for irregular natural channels. Preliminary trials indicate that results so obtained may be accepted provided the fall in the original reach does not exceed from one to two feet. When this is exceeded, additional cross sections should be surveyed.     

Evaluation of Material Biodegradability in Real Conditions–Development of a Burial Test and an Analysis Methodology Based on Numerical Vision

This work validated a burial protocol for in situ testing and presents a robust, repeatable and time-saving technique to measure degraded areas in the sample, i.e. an image analysis method. 1440 specimens of degraded samples have been compiled in a data base. To this end, twenty samples presenting different levels of biodegradability (i.e. PHBV/HV, PLA, PCL, PCL-Starch, paper, PE, PE-Starch) were buried at 4 different locations and then disinterred at 4, 6, 9, 12, 18, and 24-month intervals. The biodegradation levels of these samples were determined by computing weight and area loss. Weight loss was measured after careful cleaning, whereas area loss was quantified using image analysis. Image analysis gives reliable information on visual pollution while only requiring a rudimentary and thus quicker cleaning of the samples.     

Destruction of Wetlands and Waterbird Populations by Dams and Irrigation on the Murrumbidgee River in Arid Australia

The Lowbidgee floodplain is the Murrumbidgee Rivers major wetland in southeastern Australia. From more than 300,000 ha in the early 1900s, at least 76.5% was destroyed (58%) or degraded (18%) by dams (26 major storages), subsequent diversions and floodplain development. Diversions of about 2,144,000 ML year^–1 from the Murrumbidgee River come from a natural median flow of about 3,380,000 ML year^–1 providing water for Australias capital, hydroelectricity, and 273,000 ha of irrigation. Diversions have reduced the amount of water reaching the Lowbidgee floodplain by at least 60%, from 1888 to 1998. About 97,000 ha of Lowbidgee wetland was destroyed by development of the floodplain for an irrigation area (1975–1998), including building of 394 km of channels and 2,145 km of levee banks. Over 19 years (1983–2001), waterbird numbers estimated during annual aerial surveys collapsed by 90%, from an average of 139,939 (1983–1986) to 14,170 (1998–2001). Similar declines occurred across all functional groups: piscivores (82%), herbivores (87%), ducks and small grebe species (90%), large wading birds (91%), and small wading birds (95%), indicating a similar decline in the aquatic biota that formed their food base. Numbers of species also declined significantly by 21%. The Lowbidgee floodplain is an example of the ecological consequences of water resource development. Yanga Nature Reserve, within the Lowbidgee floodplain, conserved for its floodplain vegetation communities, will lose these communities because of insufficient water. Until conservation policies adequately protect river flows to important wetland areas, examples such as the Lowbidgee will continue to occur around the world.     

Watershed scale assessment of nitrogen and phosphorus loadings in the Indian River Lagoon basin,Florida

There is a growing evidence that the ecological and biological integrity of the lagoon has declined during the last 50 years, probably due to the decline in water quality. Establishment of a watershed scale seagrass-based nutrient load assessment is the major aim of water quality management in the Indian River Lagoon (IRL). Best estimate loadings incorporate wet and dry deposition, surface water, groundwater, sediment nutrient flux, and point source effluent discharge data. On the average, the IRL is receiving annual external loadings of 832, 645 and 94,476kg of total nitrogen (TN) and total phosphorus (TP), respectively, from stormwater discharges and agricultural runoff. The average internal cycling of TN and TP from sediment deposits in the IRL was about 42,640kg TN and 1050kg TPyr(-1). Indirect evidence suggests that atmospheric deposition has played a role in the ongoing nutrient enrichment in the IRL. The estimated total atmospheric deposition of TN and TP was about 32,940 and 824kgyr(-1), while groundwater contribution was about 84,920 and 24,275kgyr(-1), respectively, to the surface waters of the IRL. The estimated annual contribution of point effluent discharge was about 60,408kg TN and 7248kg TP. In total, the IRL basin is receiving an annual loading of about 1,053,553kg TN and 127,873kg TP. With these results, it is clear that the current rate of nutrient loadings is causing a shift in the primary producers of the IRL from macrophyte to phytoplankton- or algal-based system. The goal is to reverse that shift, to attain and maintain a macrophyte-based estuarine system in the IRL.     

Using Decision Analysis to Choose Phosphorus Targets for Lake Erie

Lake Erie water quality has improved dramatically since the degraded conditions of the 1960s. Additional gains could be made, but at the expense of further investment and reductions in fishery productivity. In facing such cross-jurisdictional issues, natural resource managers in Canada and the United States must grapple with conflicting objectives and important uncertainties, while considering the priorities of the public that live in the basin. The techniques and tools of decision analysis have been used successfully to deal with such decision problems in a range of environmental settings, but infrequently in the Great Lakes. The objective of this paper is to illustrate how such techniques might be brought to bear on an important, real decision currently facing Lake Erie resource managers and stakeholders: the choice of new phosphorus loading targets for the lake. The heart of our approach is a systematic elicitation of stakeholder preferences and an investigation of the degree to which different phosphorus-loading policies might satisfy ecosystem objectives. Results show that there are potential benefits to changing the historical policy of reducing phosphorus loads in Lake Erie.     

区域地震间接经济损失评估

对区域地震间接经济损失的研究现状进行了总结和回顾，目前主要有基于国内生产总值、基于地震震级和基于地震直接损失的3种评估计方法，对这些评估方法进行了讨论，结合地震现场的工作性质和特点，给出了现场评估的一般步骤和建议。     

基于社会公共机构的道路交通事故经济损失评价及计量模型研究

根据中国道路交通事故经济损失的研究现状,借鉴国外对道路交通事故经济损失研究的成功经验,提出适用于中国实际情况的交通事故社会公共机构服务损失费用构成;确定了道路交通事故社会公共机构服务损失评价指标体系。基于经济学和统计学理论,主要从警方服务、清障服务、管理部门服务和法律诉讼服务4个方面对道路交通事故社会服务损失进行了深层次理论分析与评价;构建了相应的评价计量模型;提出了我国评价交通事故社会服务损失的一些合理化建议。研究结果对科学、全面、合理地评价道路交通事故社会经济损失具有重要的实际意义。     

某飞机维修公司个人听力防护用品使用情况调查分析

为了解听力防护用品使用过程中的问题,提高我国噪声暴露工人听力防护用品的使用率和有效率,选择噪声危害较大的某飞机维修公司的员工,进行听力防护用品使用情况的问卷调查。结果显示:该公司为员工提供耳塞和耳罩两种听力防护用品;员工的听力保护意识、使用情况较好,使用率达95%,但对听力防护用品相关知识的了解不够全面;能够在工作中一直坚持使用的工人较少,仅占11%,影响工人工作时间使用听力防护用品时间长短的因素主要是其舒适性。调查分析提示:在未来听力防护用品的生产过程中,需要进一步加强和改善舒适性的技术;政府、企业和个人3方面共同参与,降低职业性噪声暴露对工人听力的损伤。     

PHREATOPHYTE EVAPOTRANSPIRATION AND ITS POTENTIAL REDUCTION WITHOUT ERADICATION1

ABSTRACT: The continuous availability of ground water to riparian phreatophytic vegetation results in large evapotranspiration (ET) losses in summer. Chemical or physical eradication of this vegetation can have undesirable environmental side effects. Spraying phreatophyte foliage with a nontoxic antitranspirant (AT) may reduce transpiration without eradication. Transpiration rate per unit leaf area was similar for several phreatophyte species, but ET per unit land area of phreatophytes depneds more on stand density than species. The mean ET for saltcedar in June was 8.1 mm/day measured by Bowen ratio, compared with 7.9 mm by lysimeters. ATs and growth-retardants reduced transpiration by over 50 percent in laboratory tests where foliage was thoroughly sprayed. In the field AT sprayed by a back-pack mistblower reduced ET by 20–35 percent initially and 10 percent after a month. No ET reduction occurred when AT was sprayed by helicopter on saltcedar, because excessive droplet size and heavy salt deposits on the foliage resulted in poor spray adherence. Wax-based AT was relatively nontoxic to fish and wildlife. Dissolved oxygen could be reduced for aquatic life, but further AT dilution in streams and ponds would minimize this. Helicopter spraying may affect bird nests and egg hatchability. Although ATs significantly reduce ET, their high cost and spraying difficulties preclude current use on phreatophytes. With improvement they may economically help to conserve water in riparian areas in future years.     

WATER QUALITY FROM TWO SMALL FORESTED WATERSHEDS IN SOUTHERN ILLINOIS1

Two intermittent streams on oak-hickory watersheds in southern Illinois were gaged with a V-notched weir and sampled with an automatic water sampler. For three years data were collected on flow volume and water quality. Flow volumes show large variations between years and watersheds. Samples were analyzed for Na⁺, K⁺, Ca⁺⁺, Mg⁺⁺, P, and NO^-₃. Water quality was consistently high, although there were significant differences between watersheds. A baseline for water quality has been established for comparison after one of the watersheds is clearcut at a later date.