A New Approach to Urban Rainwater Management - Science Direct

Four methods can be used for urban rainwater management: rainwater harvest, rainwater infiltration ... means rainwater is often treated as waste water which.
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Report
Mar. 2007

Journal of China University of Mining & Technology

Vol.17

No.1

J China Univ Mining & Technol 2007, 17(1): 0082–0084

A New Approach to Urban Rainwater Management ZENG Bing, TAN Hai-qiao, WU Li-juan School of Resource and Earth Sciences, China University of Mining & Technology, Xuzhou, Jiangsu 221008, China Abstract: Based on an analysis of our research results and the main problems relating to urban rainwater treatment, we propose a new approach to urban rainwater management in China. The necessity and feasibility of such a new approach are discussed. From an ecological point of view all components of the global system, including residents living in cities, have the same right to enjoy rainwater. Therefore, urban rainwater should neither be simply drained as waste water, nor be completely harvested as a kind of resource. The objective of this new approach is to maintain the natural hydrological cycle in urban areas during urbanization. When necessary, it could also be used to regulate the amount of runoff, evaporation and infiltration in a city in order to rehabilitate the hydrological cycle given the local conditions. Three basic principles should be adopted in rainwater management, i.e., separation of rainfall from sewage, limited utilization and small and decentralized facilities. Four methods can be used for urban rainwater management: rainwater harvest, rainwater infiltration, rainwater storage and rainwater pipes. The natural hydrological cycle in urban areas could be rehabilitated through rainwater management, which is of great importance for sustainable development of our cities. Key words: urban rainwater management; hydrological cycle; rehabilitation CLC number: TU 991.11+4

1

Introduction

As pointed out by UN World Water Development Report 2, “the water crisis is thus increasingly about how we, as individuals, and as part of a collective society, govern the access to and control over water resources and their benefits.” The rapid development of urbanization and the incessant expansion of urban areas have resulted in increasingly more conspicuous water shortages in cities. With narrow urban zones, large population densities and centralized production activities, water shortage is ubiquitous. 354 out of 712 cities in China, about 49.7% of the cities[1] are facing water shortage problems. At present, water shortage has become one of the most important factors which restricts the sustainable development of cities[2]. At the same time, most of the current drainage systems used in Chinese cities are centralized, which in most cases are in serious danger of collapse. That means rainwater is often treated as waste water which then cannot take part in the usual, natural hydrologi-

cal cycle. With encroaching urbanization more and more systems are proposed and to harvest rainwater directly[3]. From an ecological point of view, however, all components of the global system, including those residents living in cities, have the same right to enjoy rainwater. So urban rainwater should neither be drained off simply as waste water, nor be harvested completely as a kind of resource. To maintain a natural hydrological cycle in urban areas, a new approach is needed. Based on an analysis of our research results and the main problems relating to urban rainwater treatment, the authors of this paper explain why a new approach is necessary and how such approach should be applied.

2

Main Methods for Urban Rainwater Treatment



Modern methods for the utilization of urban rainwater first appeared in the 1980’s to 1990’s. Since then, rainwater management has drawn increasingly more attention and a series of technical standards

Received 20 July 2006; accepted 15 December 2006 Projects 40371113 supported by the National Natural Science Foundation of China and OF060096 by Young Foundation of China University of Mining & Technology Corresponding author. Tel: +86-516-83590189; E-mail address: [email protected]

ZENG Bing et al

A New Approach to Urban Rainwater Management

have been proposed for rainwater facilities used in developed countries, like Germany (DIN1989). Before 1992, a second generation rainwater utilization technology had been developed [4]. And after more than 10 years’ development and improvement, a third generation rainwater utility technology and relevant standards are under examination and are being approved. Although starting comparatively late, the utilization of urban rainwater developed rapidly in China. Besides Changdao island in Shandong province, Zhangzidao island in Dalian and Huludao island of Zhoushan in Zhejiang province, urban rainwater utilities have also been conducted in big cities like Beijing, Shanghai, Dalian, Harbin and Xi’an. In 2001, the State Department authorized “the sustainable application planning of the capital’s water resource at the beginning of the 21st century”. Since 1998, several research projects have been carried out at the Beijing Architecture Engineering School and by the Beijing water conservation office. One of them is a joint research project between the Beijing Water Resources Bureau and the University of Essen, Germany, which started in 2000. At present, urban rainwater utilization technologies can be divided into the following classes: 1) decentralized rainwater collection and reclaimed water systems in residential areas; 2) centralized water collection application and reclaimed water systems in buildings or residences; 3) decentralized rainwater infiltration systems; 4) centralized rainwater infiltration systems; 5) roof garden rainwater utility systems and 6) integrated rainwater utility systems in ecological communes (roof gardens, reclaimed water, infiltration, and waterscape). The major technology of the systems mentioned above is to prevent rainwater from becoming polluted and to rehabilitate natural hydrological cycles, which should include recovering the ability to recharge groundwater [5].

tation of the natural conduct of rainwater in urban areas given natural local conditions like rainfall, runoff, evaporation and infiltration. This will bring about obvious environmental, economic and ecological benefits, including recovery of the ability to recharge groundwater [8–9]. The best way to realize this goal is to perform rainwater management at the planning department of a city, which will reduce construction costs for its infrastructure. For urban areas, rainwater management can also be used to mitigate effectively the pressure on existing sewage networks. Only when the environmental carrying capacity gradually improves, can we have a good relation between humans and water which parallels the process of urbanization. 3.3

Key point of the new approach

A key point of the new approach to urban rainwater management is to carry out the so-called “FiveSharing” of urban rainwater. In other words, urban rainwater should be shared between life support systems and natural river systems, between human beings and all animals and plants, between runoff and infiltration, between upper and lower reaches and between the rainy season and the dry season. 3.4

Basic methods for of urban rainwater management

Until the present, many methods have been developed for urban rainwater management. All of them are based on three basic principles: 1) separation of rainfall from sewage; 2) limited utilization and 3) small and decentralized facilities. At present, combined sewage systems are used in most cities in China. In this situation, four methods can be used for urban rainwater management: rainwater harvest, rainwater infiltration, rainwater storage and rainwater pipes (Fig. 1) [10–11].

3 New Approach to Urban Rainwater Management 3.1

Characteristics of urban rainwater

In general the spatial and temporal distribution of urban rainwater is uneven and discontinuous [6]. But water demand and supply in a city should normally be steady and continuous. As the most important element of the hydrological cycle, rainwater should take part in the cycle in a natural way [7]. Unfortunately, this kind of natural way for rainwater is becoming less and less prevalent with the development of urbanization. Either it is drained as waste water into the sewage network, or it flows into rivers with occasional flooding. 3.2

Purpose of urban rainwater management

Urban rainwater management aims at the rehabili-

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Fig. 1

Basic methods for urban rainwater management

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Journal of China University of Mining & Technology

4

Benefits of Urban Rainwater Management

Literature reviews show that urban rainwater management can bring us many social, economical and ecological benefits: 1) most rainwater management systems can effectively reduce runoff and subsequent flooding in urban areas; 2) such systems can absorb urban noise, reduce the heat island effect and gradually improve the air quality and micro-climate in a city; 3) rain water collected from roads and buildings in a city can be utilized for fire fighting, lavatory washing and irrigation of green spaces; in some cases, the water can be used in factory production [12]; 4) the recharge ability of groundwater can be recovered and gradually compensate for land subsidence; 5) with the existence of decentralized rainwater management systems, pressure on traditional sewage networks can be alleviated [13]. In brief, the natural hydrological cycle in urban areas can be rehabilitated through the new approach to rainwater management, which is of great importance for sustainable development of cities.

5 Conclusions

Vol.17

No.1

conclusions: 1) a new approach to urban rainwater management is necessary and feasible; it aims at the rehabilitation of the natural way for rainwater in urban areas given the natural local conditions; 2) the major point of this approach to urban rainwater management is to carry out the so-called “Five-Sharing” of urban rainwater, in other words, urban rainwater should be shared between the life support system and natural river system, between human beings and all animals and plants, between runoff and infiltration, between the upper and lower reaches, and between the rainy season and the dry season; 3) three principles, i.e., separation of rainfall from sewage, limited utilization and decentralization should be adopted in rainwater management; 4) four methods can be used for urban rainwater management: rainwater harvest, rainwater infiltration, rainwater storage and rainwater pipes; 5) the natural hydrological cycle in urban areas can be rehabilitated through rainwater management; this new approach to urban rainwater management is of great importance for sustainable development of our cities.

Based on our analysis, we can draw the following

References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

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