The 1,056 meter causeway that carries water from Johor Bahru, Malaysia to Singapore. Photo courtesy mohamed.shaaz/flickr.com

Twenty years ago, the world’s megacities, defined by the United Nations as urban agglomerations with over 5 million inhabitants, housed 308 million people—6 percent of the world’s population at that time. Now, this number is estimated to be 520 million people, which is 9 percent of all humans.

According to the 2004 UN Prospects, the median growth of the megacities in high-income countries is expected to be slightly below 3 percent in 2000-2015. High-middle income countries’ megacities will grow 11 percent, whereas in low-middle income countries, the growth is already 27 percent. The situation looks quite different in low-income country megacities, which are expected to grow 48 percent, with poorer cities such as Lagos and Dhaka reaching even 73 percent.

According to the United Nations Population Bureau, in the poorest regions of Africa and Asia, less than two out of five people live in urban areas, whereas in most other regions the figure is over four out of five. This means that the urbanization of the poorest regions may occur over the next several decades.

A Living Thing

A megacity is like an enormous organism with a peculiar metabolism. Besides natural biogeochemical and ecological cycles, it relies on man-made veins that constitute enormous technical, institutional, financial, and social agglomerate systems that allow the urban areas to continue living. One key part of this vein system is the water infrastructure. Estimates of the availability of adequate water and sanitation services in the world’s urban areas vary. The World Health Organization (WHO) and The United Nations Children's Fund (UNICEF) assessed in 2000 that 15 percent of the population of Africa lacked access to an appropriate water source. By contrast, the United Nations Human Settlements Programme (UN-HABITAT) estimated that the figure is between 35 and 50 percent. A reduction in the number of people with inadequate water sources is one of the UN Millennium Targets. The problem is vast and its true dimension seems to be obscured.

Whereas in traditional rural societies, organic matter, nutrients and other materials are largely recycled, this is not the case in urban areas. Massive amounts of goods and materials are transported over long distances to reach urban users. They are not, however, returned to the originating ecosystems, but discharged in the immediate environment of the large-density populations. There, the water carrying this waste can become contaminated and pose an immediate health risk to the megacity’s inhabitants.

Case Studies in Megacity Water Infrastructure

A closer examination of several case studies drawn from a study by Third World Centre for Water Management in Mexico (Linkoping University and Helsinki University of Technology) is necessary to explore the subject more thoroughly.

In Dhaka, Bangladesh, the shortcomings of water infrastructure, worsened by dramatic flooding, have caused serious surface and groundwater pollution with detrimental health effects. Storm water management systems have been developed, but these have failed to keep pace with the growing population. Decades ago, the city was covered by a network of 24 canals and included a large area of natural wetlands. This system was able to minimize flood damage, but the unplanned and largely illegal urban sprawl has led to the non-existence of proper storm-water infrastructure.

Water is a lucrative commodity for business, particularly among urban squatters for whom traditions and old customary water rights have faded away. In Karachi, Pakistan, the poor must pay up to 40 times the official water price to vendors, while the official price is applied to the middle and upper income sections of the population who receive water piped into their homes. For others, private wells are common and water drawn from them originates from diverse urban sources, including leaking sewage pipes. Health risks are high.

Mexico City grew on the site of the ancient Aztec capital in a valley enclosed by mountains. Rapid growth has caused a decline in the quality of life in the city, which has become overcrowded, polluted, and short on such basic amenities as water. A mere 9 percent of Mexico City’s wastewater is treated. Due to inadequate strategic planning, severe shortcomings persist in the maintenance and systematic development of infrastructure. Disproportionately, the affected are poor. The construction of the infrastructure needed to bring progressively increasing amounts of water to the metropolitan area as well as to drain and clean the waste water is neither socioeconomically feasible nor environmentally sustainable. Costs are skyrocketing and the benefits go mostly to the well-to-do.

Singapore is a fast growing city that has advanced from a poor harbor town to an ultramodern business hub. Its water systems are equally astonishing today. Singapore island is physically far too small to provide enough water for its inhabitants. The city has had a 100-year contract to import water from neighboring Malaysia since 1961 but prefers now to reduce this dependency. Consequently, it has imposed stringent technical and managerial improvements on its water sector. It tops the world’s large urban areas with the reduction of water losses, the water consumption per capita has been cut by tariff policies, the island’s green areas are strictly protected, the water catchments are kept in excellent state, and the city has invested billions in high-tech water purification. Singapore has launched the term NeWater to make the reclaimed wastewater more acceptable since treated wastewater is increasingly used as a raw water source to the city’s water system. Singapore is also relying more and more on desalinated sea water.

Beijing lies at the border of the Gobi desert, a highly challenging location with respect to water. The natural water sources have been vastly overexploited, and the groundwater table has sunk from a few meters below the land surface to over 50 meters. Within the past decades, the solution to the water shortage has been a long-distance water transfer system from the Yangtze basin, over 1000 kilometers to the south. The transfer canals were planned to convey more than the discharge of the Nile River to the dry North China Plain. While the massive works have continued over two decades, political and economic modernization has changed the rules of the game. The original concept was based on central planning of water resources, guaranteeing an adequate allocation of water for all parts of China with massive infrastructure. Now, the priority concerns are economical and environmental; Beijing municipal authorities are unwilling to purchase the costly and risky Yangtze water. Instead, they invest in high-technology water infrastructure including elaborate water demand management, minimization of network losses and purification methods, such as the re-use of water. The paradigm seems similar to that which Singapore has already adopted.