A CRAZY IDEA ON URBAN WATER MANAGEMENT?1

ABSTRACT. High percentage of imperviousness in the city is the source of storm runoff. Roof area contributes significantly to the imperviousness. An attempt to make use of roofs as urban flood control device and water conservation measure is advocated. Two different schemes, one for built-up industrial-commercial area, the other for residential area, are suggested. The former utilizes the roof as detention reservoir for flood control, the latter employs recharge pit to convert runoff into ground water resource. The proposed schemes are not only hydrologically, hydraulically and structurally sound but also economically feasible. It is worth considering in the future planning of urban renewal and urban development.     

EFFICIENT MANAGEMENT POLICIES FOR URBAN WATER SUPPLY1

ABSTRACT .This paper attempts to spell out the difficult conditions faced by urban water supply managers in achieving overall efficiency. Based upon these conditions, and changes that are likely in the next decade, it then tries to suggest strategies that would lead to even higher levels of efficiency in the future. A blending of political and economic concepts is used to make what is hoped to be a realistic analysis. What do we mean by “efficient”? The usual welfare economics definition is attainable only under a very special and highly unrealistic set of institutional arrangements. As soon as we delegate responsibility to a specialized agency we provide the opportunity, indeed we make it imperative that, in a social sense, a sub-optimization will take place. From the specifics of the indictment of this sub-optimization we can learn something about the opportunities for more efficient management in the future. In general there is an under-exploitation of multiple-function, multiple-objective opportunities. The pressures for sub-optimization hinge very directly on the sources of support and opposition to the water supply agency. A change requires the creation of a broader political base. The search for regional solutions is largely a political problem, and probably the development of flexible, responsive regional agency, so long sought, is still the answer.     

A new role for citizens’ initiatives: the difficulties in co-creating institutional change in urban planning

In this paper, we analyze the institutional work that underlies the attempt to institutionalize a more active role of citizens in urban planning. We draw on a case in which a group of citizens aims to redevelop a brownfield site into a vital urban area. This citizens’ initiative is co-creating a new form of urban planning with the municipality, private organizations and individual citizens. The study shows how citizens’ initiatives can be a driver for institutional change, but that uncertainties about new institutions tend to reinforce the maintenance of existing ones. This paradox explains why even if the ambition for a new form of planning is widely shared, actually realizing institutional change can still be difficult and time-consuming.     

基于GIS的芜湖市城市用地扩展规律

利用芜湖市1990年、2000年两个时相的遥感影像进行城市土地利用解译,提取城市新、旧建成区区块用地,通过GIS软件提供的空间统计分析功能,对城市用地空间分布进行定量分析与描述,从而揭示城市用地及其扩展规律.研究结果表明,芜湖市用地扩展呈现明显中心圈层式蔓延和轴向集中性扩展规律的模式.作者提出了城市用地扩展中应注意解决的问题.     

城市河流近自然治理--概念构架与治理设计

河流是城市生态系统的重要组成部分,是城市的自然元素和景观组分,具有提供水生生物生境和水源、调节小气候、美化城市、休闲娱乐等多种生态服务功能.随着城市化进程的飞速发展,城市河流生态系统面临着生物多样性减少、污染加剧等多方面的危害.如何恢复受损的城市河流生态系统已经成为我们的当务之急.对城市河流的生态结构及其在城市中的生态功能进行了简要介绍,讨论了河流生态恢复的近自然方法,并对现有的河流生态恢复存在的问题及发展趋势提出了几点看法.     

山东省城镇空间格局

城镇是人类活动影响地表的最主要形式,是土地利用/土地覆盖变化的主要方面.山东省是中国东部沿海大省,土地利用处于不断地调整过程中.在全省城镇空间分布格局现状的基础上,结合中心地理论,运用数据包络分析(DEA)方法进行了具体分析,对全国土地利用/土地覆盖的深入研究具有重大意义.     

我国城市周边规划建设用地利用探讨

随着我国城市面积的不断扩大，大量的郊区耕地成为或即将成为城市的建设用地，同时与城市建设相伴相随的建筑渣土的堆放已成为城市的一大问题，本文按照循环经济原则，提出利用规划期内即将建设的城市周边耕地资源建立供应城市建筑的制砖企业，同时利用取土坑填埋建筑渣土，建立城市物质的有效循环，实现城市建筑的循环经济。并对此物质循环方式做了生态经济的分析，也对此物质循环中存在的障碍提出了解决的方法。     

USE AND EFFECTIVENESS OF MUNICIPAL WATER RESTRICTIONS DURING DROUGHT IN COLORADO1

ABSTRACT: Drought conditions in the summer of 2002 prompted several cities along Colorado's Front Range to enact restrictions on outdoor water use, focusing primarily on limiting the frequency of lawn watering. The different approaches utilized by eight water providers were tracked to determine the level of water savings achieved, measured as a comparison of 2002 usage to 2000 to 2001 average usage, and also based on a statistical estimate of 2002 “expected use” that accounts for the impact of drought conditions on demand. Mandatory restrictions were shown to be an effective tool for drought coping. During periods of mandatory restrictions, savings measured in expected use per capita ranged from 18 to 56 percent, compared to just 4 to 12 percent savings during periods of voluntary restrictions. As anticipated, providers with the most stringent restrictions achieved the greatest savings.     

CONNECTING GROUND WATER INFLUXES WITH FISH SPECIES DIVERSITY IN AN URBANIZED WATERSHED1

ABSTRACT: Valley Creek watershed is a small stream system that feeds the Schuylkill River near Philadelphia, Pennsylvania. The watershed is highly urbanized, including over 17 percent impervious surface cover (ISC) by area. Imperviousness in a watershed has been linked to fish community structure and integrity. Generally, above 10 to 12 percent ISC there is marked decline in fish assemblages with fish being absent above 25 percent ISC. This study quantifies the importance of ground water in maintaining fish species diversity in subbasins with over 30 percent ISC. Valley Creek contains an atypical fish assemblage in that the majority of the fish are warm‐water species, and the stream supports naturally reproducing brown trout, which were introduced and stocked from the early 1900s to 1985. Fish communities were quantified at 13 stations throughout the watershed, and Simpson's species diversity index was calculated. One hundred and nine springs were located, and their flow rates measured. A cross covariance analysis between Simpson's species diversity index and spring flow rates upstream of fish stations was performed to quantify the spatial correlation between these two variables. The correlation was found to be highest at lag distances up to about 400 m and drop off significantly beyond lag distances of about 800 m.     

REVIVING URBAN STREAMS: LAND USE,HYDROLOGY, BIOLOGY,AND HUMAN BEHAVIOR1

ABSTRACT: Successful stream rehabilitation requires a shift from narrow analysis and management to integrated understanding of the links between human actions and changing river health. At study sites in the Puget Sound lowlands of western Washington State, landscape, hydrological, and biological conditions were evaluated for streams flowing through watersheds with varying levels of urban development. At all spatial scales, stream biological condition measured by the benthic index of biological integrity (B‐IBI) declined as impervious area increased. Impervious area alone, however, is a flawed surrogate of river health. Hydrologic metrics that reflect chronic altered streamflows, for example, provide a direct mechanistic link between the changes associated with urban development and declines in stream biological condition. These measures provide a more sensitive understanding of stream basin response to urban development than do treatment of each increment of impervious area equally. Land use in residential backyards adjacent to streams also heavily influences stream condition. Successful stream rehabilitation thus requires coordinated diagnosis of the causes of degradation and integrative management to treat the range of ecological stressors within each urban area, and it depends on remedies appropriate at scales from backyards to regional storm water systems.