Urban Water最新文献

This paper provides a comprehensive (although not exhaustive) overview of the physical/mechanical models that have been developed to improve the understanding of the structural performance of water mains. Several components have to be considered in modelling this structural behaviour. The residual structural capacity of water mains is affected by material deterioration due to environmental and operational conditions as well as quality of manufacturing and installation. This residual structural capacity is subjected to external and internal loads exerted by the soil pressure, traffic loading, frost loads, operational pressure and third party interference. Some models address only one or a few of the numerous components of the physical process that lead to breakage, while others attempt to take a more comprehensive approach. Initial efforts were aimed mainly towards development of deterministic models, while more recent models use a probabilistic approach to deal with uncertainties in defining the deterioration and failure processes. The physical/mechanical models were classified into two classes: deterministic and probabilistic models. The effect of temperature on pipe breakage is discussed from three angles; the first deals with temperature effects on pipe-soil interaction, the second deals with frost load effects and the third provides a brief review of various attempts to statistically quantify influence of temperature on water main failure.

This paper complements the companion paper “Comprehensive review of structural deterioration of water mains: statistical models”, which reviews statistical methods that explain, quantify and predict pipe breakage or structural failures of water mains.

Groundwater is of major importance in providing municipal water-supply and for private domestic and industrial use in many urban centres. The subsurface has also come to serve as the receptor for much urban and industrial wastewater and for solid waste disposal, especially in the developing world. In result, there are rather widespread indications of degradation of the groundwater resource-base caused by excessive exploitation and/or inadequate pollution control. This paper is based primarily on the detailed investigation of six cities in Latin America and Asia. Fuller details are to be found in a related World Bank publication entitled `Groundwater in Urban Development' (Foster, Lawrence, & Morris, 1998). The objective of the present paper is to raise awareness of the interdependence of groundwater and urbanisation among urban policy-makers and to provide a framework for systematic consideration of groundwater in urban management.

This paper provides a comprehensive (although not exhaustive) overview of a large body of work carried out in the last 20 years to quantify the structural deterioration of water mains by analysing historical performance data. The physical mechanisms that lead to pipe failure often require data that are not readily available and are costly to obtain. Thus, physical models may currently be justified only for major transmission water mains, where the cost of failure is significant, whereas statistical models, which can be applied with various levels of input data, are useful for distribution water mains. The statistical methods are classified into two classes, deterministic and probabilistic models. Sub classes are probabilistic multi-variate and probabilistic single-variate group processing models. The review provides descriptions of the various models including their governing equations, as well as critiques, comparisons and identification of the types of data that are required for implementation. In some cases, a brief description of the methodology is provided where a decision support system was developed based on a specific statistical model.

A companion paper “Comprehensive review of structural deterioration of water mains: physical models” helps to complete the picture of the work that has been done on the subject of water main deterioration and failure.

Theoretical principles of sustainable aquifer management are laid out in this work. The premise of our treatment is that groundwater is a renewable, although depletable, natural resource. The theory of this work is aimed at aquifers with a relatively homogeneous recharge that can be approximated by a logistic growth function. Sustainable aquifer exploitation occurs when the rate of groundwater extraction is equal to or less than the natural rate of groundwater replenishment for any level of aquifer storage. There can be many levels of sustainable aquifer exploitation depending on the level of aquifer storage, but there may be only one which maximizes economic returns under a variety of economic and aquifer conditions. Different strategies for sustainable exploitation are derived depending on whether or not the analysis considers tradeoffs among (i) current and future exploitation, (ii) constant and dynamic aquifer storage conditions, and (iii) regulated and unregulated aquifer exploitation. Key factors affecting sustainable exploitation strategies include (1) the market price of groundwater; (2) the cost of groundwater extraction; (3) the aquifer storage and natural replenishment characteristics; (4) institutional and environmental regulations on groundwater extraction; and (5) the real discount rate. An example of sustainable groundwater exploitation in Santa Barbara, California, illustrates the methods of this paper.

This paper addresses the problem of how to diagnose the effect of stormwater infiltration on groundwater quality variables and to capture the complex nonlinear relationships that exist between groundwater quality variables. It is argued that because of the complex nonlinear relationships between the groundwater quality variables, classical linear statistical methods are unreliable and difficult to visualise the results. The application of intelligent techniques, which can analyse the multi-dimensional groundwater quality data with the sophisticated visualisation technique, is vital for sustainable groundwater management.

In this paper, the Kohonen self-organising feature maps (KSOFM) neural network is applied to analyse the effect of stormwater infiltration on the groundwater quality, and diagnose the inter-relationship of the groundwater quality variables in a fractured rock aquifer. Based on the pattern analysis visualised in component planes and U-matrix, the inter-relationships among the groundwater quality variables due to the stormwater infiltration are extracted and interpreted. The pattern distribution of groundwater quality variables due to different aquifer conditions is also analysed.

It is concluded that the KSOFM technique described in this paper provides an effective analysing and diagnosing tool to understand the dynamic in the groundwater quality and to extract knowledge contained in the multi-dimensional data. Finally it has considerable potential not only in groundwater quality monitoring and diagnosis, but also in other environmental areas.

Sustainable groundwater management must take into consideration pollution sources and the potential of fluid percolation which could convey pollutants to the aquifer. The objective of this paper is to highlight the relationship between environmental factors and land-use types, and the adverse effects upon groundwater quality which may stem from that relationship. A clear understanding of the significant impact of land-use can generate guidelines for sustainable groundwater management. Appropriate conservation and remediation measures, could then be suggested, taking in consideration land-use and intensity of percolation potential from the ground surface to the water table. Guidelines for operational measures can be suggested to mitigate and correct adverse trends in groundwater quality. Integrated with such guidelines, planned land-use activities should harmonize with needs of both ecological and sustainable groundwater management. Two study areas located in different regions of Israel's coastal aquifer have been considered in this paper. Erez-Shiqma represents a pristine region, whilst the Ra'anana area represents a region suffering from significant eco-hydrological stress.

The trihalomethane formation potential (THMFP) was measured in groundwaters affected by infiltration of wastewater or landfill leachate from Mexico, Jordan and Thailand. THMFP was directly related to the concentration of dissolved organic carbon (DOC), except where leachate was produced from burnt waste or where bromide concentrations were unusually high indicating the proportion of brominated derivatives was dependent on the concentration of bromide. It is proposed that the THMFP provides a sensitive measure of low levels of organic contamination and can be used as a surrogate for DOC concentration where there are difficulties in measuring this parameter. A risk assessment model has been used and demonstrates indirect health effects due to the chlorination of leachate contaminated groundwater.

Over the past five years there has been an ever increasing amount of independent research directed at understanding how siphonic roof drainage systems perform hydraulically. Since 1995, there has been a substantial amount of time and money invested in researching these systems by both government and industry. This increased amount of research activity means that, increasingly, publications are entering the public domain – the main source of this work being UK-based. This text aims to collate this work, and give an overview of what the current level of understanding is. Furthermore, it will analyse what this research means for existing systems, and recommend areas for future research in this field.