The global urban population is expected to grow by up to 2.5 billion people by 2050, with an increase to the overall number of megacities which generate unique pressure on water supplies. How, then, can we manage this expansion in a sustainable way and create new cities that don’t do irreparable damage to the water cycle?
Growth of megacities and the impact on water
The global population has increased hugely over the past century and this has included the proliferation of megacities. A megacity is defined as an urban area with a population of over 10 million. In 1950, only two cities in the world – New York and Tokyo – had populations of this size. Today, there are 33 listed megacities across the world and this is expected to increase to around 48 by 2030, by which time it is expected that around 60% of the world’s population will live in urban areas (with nearly 15% living in megacities).
The existence and growth of megacities adds to the growing pressure on global freshwater supplies as well as posing other environmental challenges. With more people needing water, it is essential that resources are managed effectively and the infrastructure can cope with the demand. A further challenge is that over half these megacities are in developing areas of the world. The UN has recognized the need to address these issues and has created the Megacities Alliance for Water and Climate (MAWAC).
The main problems
Megacities exemplify some of the gravest problems we face as a global population when it comes to managing and sustaining our water supplies. We are facing a number of challenges in the coming decades such as climate change, population growth and inefficient water management practices and these are most evident in our busiest cities. Problems such as:
- Over-use of water – growing populations generate additional demand on water supplies and industrialised areas have the added problem of over-using freshwater supplies in water-intensive industrial and agricultural practices. Of the 11 cities identified as most likely to run out of drinking water, 10 of them are classified as megacities or on the verge of becoming a megacity.
- Infrastructure problems – there are two problems at play here. In developed cities such as New York, London and Paris, we see problems of outdated centralized infrastructure struggling to meet demand and wasting billions of gallons daily in leaks. Developing cities, meanwhile, often lack the infrastructure capacity to provide even basic clean water to the whole of the population. This has knock-on effects such as disease and health problems.
Insufficient protection against floods – global warming has led to the rise of extreme weather including increased floods. Reports have highlighted that megacities, especially in developing countries in Asia, face increased flooding risks that could have an economic cost of up to $1 trillion a year.
We need to act now if we are to avert a future water crisis that will do untold damage to the world’s megacities as well as other areas. The world needs a new water vision which centres around reviewing and changing its outdated and unsustainable water practices.
Our most prosperous and populated cities can thrive in the future if they make the necessary changes. These need to include:
- recycling and more use of alternative water sources – moving from a linear water use model which relies heavily on exploiting finite groundwater and freshwater resources to a circular model which incorporates reusing wastewater, harvesting rainwater and transforming saltwater supplies will greatly reduce the water footprint of the world’s megacities.
- Utilising technology to manage water supplies more efficiently – this can be done at household, commercial and governmental level and involves making use of the newest smart technology (e.g. sensors, leak detection equipment, smart meters and data sharing equipment) to reduce waste and use water supplies in the most efficient ways possible.
- Becoming more eco-friendly and weather-resilient in design – to protect against future flood risks, cities can look to redesign themselves to better absorb stormwater, e.g. by moving towards the “sponge city” model.
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