Chemical Technology January 2016

Water for a sustainable world Urbanisation by Bhushan Tuladhar, Andre Dzikus and Robert Goodwin, all of UN-Habitat United Nations Human Settlements Programme)

Over the past several decades, ever-growing demands for – and misuse of – water resources have increased the risks of pollution and severe water stress in many parts of the world. The frequency and intensity of local water crises have been increasing, with serious implications for public health, environmental sustainability, food and energy security, and economic development. Although the central and irreplaceable roles that water occupies in all dimensions of sustainable development have become progressively recognised, the management of water resources and the provision of water-related services remains far too low on the scales of public percep- tion and of governmental priorities. As a result, water often becomes a limiting factor, rather than an enabler, to social welfare, economic development and healthy ecosystems. The fact is there is enough water available to meet the world’s growing needs, but not without dramatically changing the way water is used, managed and shared. The global water crisis is one of governance, much more than of resource availability, and this is where the bulk of the action is required in order to achieve a water-secure world. Prologue: The future of water – A vision for 2050 by Richard Connor, Joana Talafré, Karine Peloffy, Erum Hasan and Marie-Claire Dumont, all of WWAP

Water in a rapidly urbanising world Cities have become the place where development chal- lenges and opportunities increasingly come face to face. In 2014, 3,9 billion people, or 54 % of the global population, lived in cities, and by 2050, two-thirds of the global popula- tion will be living in cities (United Nations Department of Economic and Social Affairs - UNDESA, 2014). Furthermore, most of this growth is happening in developing countries, which have limited capacity to deal with this rapid change. Cities impact the hydrological cycle in several ways by: • extracting significant amounts of water from surface and groundwater sources; • extending impervious surfaces thus preventing recharge

of groundwater and exacerbating flood risks; • polluting water bodies through the discharge of untreated wastewater. Since much of the water consumed by cities generally comes from outside the city limits, and the pollution they generate also tends to flow downstream, the impact of cities on water resources goes beyond their boundaries. Cities also import significant amounts of food, consumer goods and energy from outside the city, which requires large amounts of water at the point of production, transportation and sale, this virtual demand of cities greatly exceeds direct water use (Hoekstra and Chapagain, 2006). At the same time, as centres for innovation, cities provide

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Chemical Technology • January 2016