HYDROLOGIC RESPONSE TO PUMPING AND CONTAMINANT ADVECTION IN A FRACTURED ROCK ENVIRONMENT1

ABSTRACT: Ground water flow and supply at the Whiteshell Research Area (WRA) in southeastern Manitoba and the advective movement of contaminants from a hypothetical nuclear fuel waste disposal vault to the adjacent biosphere and a nearby ground water supply well are simulated using finite-element modeling and numerical particle-tracking technique. The hypothetical vault is located at a depth of 500 m, below the water table, in low-permeability plutonic rock of the Canadian Shield. The rock mass is intersected by high-permeability fracture zones (aquifers), which also act as conduits for vault contaminants to migrate to the ground surface. The ground water resource is, therefore, limited in quantity and quality and should be explored with care. A 30 m deep well, which pumps water at a rate of 120 m³/yr from a low-dipping fracture zone, LD1, reduces natural discharge from the system to augment natural recharge. At this pumping rate, a 100 m or 200 m deep well neither reduces discharge nor induces recharge into the system. Thus, at the WRA, a 30 m deep domestic water supply well best meets the water requirements of a one-person household at the rate of 120 m³/yr. The 100 m and 200 m wells best meet the requirements of a family of six and a family of six with light irrigation, respectively, without capturing contaminants’pathways from the vault to the ground surface. By virtue of the proximity of the 200 m well intake to the hypothetical vault, this well performs best as a purge well at pumping rates of 0,000 m³/yr and greater. Finite-element modeling is useful in evaluating the water supply potential of a fractured rock environment in which a nuclear waste disposal vault is proposed to be sited.     

HEAD LOSS AT MANHOLES IN SURCHARGED SEWER SYSTEMS1

ABSTRACT: A laboratory investigation was conducted to determine the head losses at sewer pipe junctions (manholes) under surcharged conditions. A physical model of a manhole/pipeline system was constructed for head-loss measurements. Head-loss coefficients were determined for a variety of outlet-flow Reynolds numbers, surcharge levels, pipe sizes, flow configurations, and inlet-flow rates. Empirical formulas were also developed to estimate head-loss coefficients. The results indicate that head loss is insensitive to the amount of surcharge, but depends heavily on the flow configuration, relative flow rate, and the change of pipe diameter within the pipelines.     

湿地可持续发展与经济损益的理论分析

文章分析了中国湿地可持续发展的基本内涵和人为干扰的限制因子，建立了湿地人为干扰破坏损益分析技术路线，提出了经济损益分析理论模型及损益度计量模型。     

湖滨河口湿地中磷的输移转化机制及截留效应研究进展

湖滨河口湿地对湖泊的水质与生态健康有重要影响,但其对营养物质的截留效应亦备受争议.因此深入了解营养物质在湿地"水-底泥-植物"中的输移转化过程,明确导致湿地"源-汇"功能转换的主要驱动机制与关键影响因子具有重要意义.本文以磷(P)为对象,分析了水文过程的变异性对湖滨河口湿地的影响,综述了湿地截磷的植物机制、微生物机制及"上覆水-底泥"界面过程,比较了短期和长期机制的差异;识别了湿地截P的重要影响因素及其交互反馈过程,主要包括水文条件、底泥理化性质、离子含量、水生植物种类等;总结了目前已开展的野外监测、室内培养、吸附等温线、统计分析、机理模型等研究方法,提出未来需将湿地水文模型与生态模型相结合,用于识别和评估磷在湿地"水-底泥-植物"系统中的输移关键过程及截留效应.     

MODELING A CONCRETE BLOCK IRRIGATION DIVERSION SYSTEM1

ABSTRACT: Concrete block irrigation diversion systems have been proposed as alternatives to permanent dams of concrete or rock or temporary gravel berms. Permanent dams can cause stream channel instability, bank erosion, sediment pollution, ice flow blockage, and safety problems for recreational floating craft. Temporary berms can require substantial streambed disturbance and can promote sediment pollution, stream bank instability, and bank erosion. A design procedure was developed based on a model of the hydraulic performance of concrete block diversion systems. The procedure was used to model a site on the Gallatin River in Montana. The method relies on HEC-RAS (Hydrologic Engineering Center -River Analysis System) software combined with analytical techniques in an iterative scheme. The hydraulic performance of different diversion configurations (the existing heavy-rock diversion system, concrete blocks oriented parallel to flow, and concrete blocks oriented diagonally) was assessed using the model under a range of flow rates. The minimum diversion dimensions (length, number, and size of blocks) that maintained block stability while diverting the requisite flow were determined for each model run. At the Gallatin River site, the block system oriented parallel to flow required less diversion material than the diagonal orientation. The recommended diversion length was 51.8 m (170 ft). Trapezoidal blocks with a top width of 20.3 cm (8 in), a height of 45.7 cm (18 in), and side slopes of 2 vertical to 1 horizontal were specified. This configuration minimizes the total block mass, diverts the required flow, and has a factor of safety of 2.0 against block displacement.     

关于保护湿地资源改善环境的思考

阐述了保护湿地的重要意义，结合实际分析了保护湿地工作中亟待解决的实际问题，并提出了切实做好保护湿地工作的对策与建议。     

INCORPORATING UNCERTAINTY IN THE DESIGN OF STREAM CHMNEL MODIFICATIONS1

ABSTRACT: The designs of stream channel naturalization, rehabilitation, and restoration projects are inherently fraught with uncertainty. Although a systematic approach to design can be described, the likelihood of success or failure of the design is unknown due to uncertainties within the design and implementation process. In this paper, a method for incorporating uncertainty in decision‐making during the design phase is presented that uses a decision analysis method known as Failure Modes and Effects Analysis (FMEA). The approach is applied to a channel rehabilitation project in north‐central Pennsylvania. FMEA considers risk in terms of the likelihood of a component failure, the consequences of failure, and the level of difficulty required to detect failure. Ratings developed as part of the FMEA can provide justification for decision making in determining design components that require particular attention to prevent failure of the project and the appropriate compensating actions to be taken.     

我国湿地保护的法律思考

湿地是一种不同于陆地和海洋的特殊生态系统，具有重大的经济、生态和教育价值。长期以来，我国对湿地的价值认识不足，对湿地过度地开发利用，也未进行有效的保护，使之遭到了前所未有的破坏。我国对湿地保护的法律规范多散见于其他相关的法律法规之中。没有一部专门的法律规范对其进行调整，与我国严峻的湿地保护形势不相适应。本文针对我国湿地保护法律制度中存在的问题，提出了完善我国湿地保护的若干法律构想。     

Stable isotope dynamics of nitrogen sewage effluent uptake in a semi-arid wetland

Our objectives were to determine (1) how much N is transferred into the food web via plants from a wetland receiving not only inputs of treated sewage effluent, but also containing contaminants such as polychlorinated biphenyls (PCBs), (2) how birds, as consumers, utilize exogenous N and uptake PCBs in relation to the food web of the wetlands, (3) the feasibility of using isotopic analysis in estimating trophic levels in a semi-arid system. Our results demonstrate that there is very high spatial variability in the N isotopic composition of primary producers. Birds had lower variability in delta15N, despite feeding at multiple trophic levels. In very high spatial variability in delta15N of primary producers, it is difficult to use N isotope techniques to define trophic levels relevant to the bioaccumulation of organic pollutants, but it is possible to track the flow of exogenous N through the food web.