Page 517 - Shaping smarter and more sustainable cities - Striving for sustainable development goals

3.1 Rapid urbanization

Cities around the world are continuously providing financial and specialized services for businesses,
industry, and manufacturing sectors, among others. The emergence of new markets has contributed
to a sharp population increase, fostering urbanization. The global urban population is estimated to
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be 3.5 billion of inhabitants, and is expected to surpass 5 billion by 2030 . This rapid growth engulfs
outlying towns and blurs rural/urban boundaries creating peri‐urban areas, areas immediately
adjoining urban areas that are localized outside formal urban boundaries and urban jurisdictions,
and in some regions, urban corridors, city chains and megacities.
Megacities and metacities – defined by the UN‐Habitat as cities with more than 10 million
inhabitants or 20 million inhabitants respectively – are growing rapidly, particularly in developing
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countries of Asia, Latin America and Africa . It is estimated that by 2025 there will be 27 megacities,
21 of which will be located in developing countries. Projections suggest that by 2015, Bombay (22'6
million inhabitants), Dhaka (22'8), Sao Paulo (21'2), Delhi (20'9) and Mexico City (20'4) will be among
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the six biggest megacities, each surpassing 20 million inhabitants (Figure 3).

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Source: Kraas and Nitschke (2008).
Figure 3 – Projected megacities, 2015

These highly concentrated populations and the increasing size of cities have posed severe strains in
local water resources, as cities are confronted by the need to meet an increasing demand for water
resources. In the case of many cities, responding to this high demand has led to unsustainable water
usage and over abstraction, and a depletion of groundwater and rivers that has serious
consequences on water sources and on the environment. These challenges can have severe effects
in megacities located in arid and semi‐arid areas, particularly as climate change impacts further
constrain their ability to provide access to a reliable and clean supply of water.
The inability to provide citizens with the necessary infrastructure has caused other problems,
including the growth of the informal supply of drinking water, wastewater collection and disposal

ITU‐T's Technical Reports and Specifications 507