Since the year 2007 there is an equal share of people living in cities and in rural areas (Tibaijuka 2006). The process of urbanisation may still be increasing in industrial nations, however, the process of the extreme dynamic of growth of the megacities of the North has been declining since the middle of the twentieth century. By contrast there is still a strongly increasing growth of urban areas. At large that means that the number of megacities will continue to rise. Nowadays we speak of 39 megacities worldwide of which 28 are located in developing countries. Cities in Africa and Asia are the ones growing the fastest.
Business district in Guangzhou, Southern China
Consequences of urbanisation on water resources
Processes of urbanisation have a negative influence on the availability and quality of water resources. Often the hydrological and hydrogeological basis of an area is strongly affected by processes of urbanisation in these countries.
Changes of the structure of urban development going along with the urbanisation will not be without consequences for the environment and water resources (Wehrhahn et al. 2008). Consequences for ground water resources are fluctuation of groundwater level and serious pollution of ground water through diverse sources of urban pollutants (Foster et al. 1993; Morris et al. 1994; Vasquez-Sune et al. 2005). Especially in developing and threshold countries, but also in industrialised countries, the so-called urban regeneration of ground water conditioned by canal leakage and/ or missing sanitation systems lead to a strong contamination of ground water (Morris et al. 1994; Lerner & Barrett 1996; Chilton 1999; Putra 2007). Furthermore, urban systems often exhibit a fast feedback between wastewater, surface water and ground water (Azzam et al. 2009).
Informal settlements in the research area Guangzhou
In megacities formal as well as informal dynamics influence further developing processes. In many cases these formal and informal processes exist side by side and are therefore difficult to separate and differentiate.
In centralistic authoritarian systems such as China informal factors and processes in the development of urban areas do not occur in such an excessive way as they do in decentralised democratic countries. Nevertheless, informal influences on formally planned settlement structures exist on a considerable scale. The role of uncontrolled factors working on a local level with influence on formally planned and structured cities in China is getting more and more important, among other things because of the economic liberalisation of the so-called special economic area.
Within the scope of German Research Foundation priority program 1233 “Megacities: Informal dynamics of global change” the Department of Engineering Geology and Hydrogeology of RWTH Aachen University investigates together with other partners on the influences of formal and informal dynamics in megacities by means of the medium water using the example of the south Chinese city Guangzhou with respectively 11 million inhabitants.
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