What is the one natural substance that is MOST vital to life on Earth? Water. Without water, life is impossible for most creatures and plants.

Clean water is essential to life, and as the Earth's population grows, water is becoming more and more a limiting factor to human life. Concentrating populations in cities places additional demands on our ability to supply growing urban areas with adequate fresh, clean water. Water is becoming our most valuable resource, especially in urban areas.

Today, half of the planet's population lives in urban areas and the world's cities and towns are growing at an unprecedented rate. According to the United Nations (World Urbanization Prospects: The 2009 Revision), the urban areas of the world are expected to absorb all the population growth expected over the next four decades while at the same time drawing in some of the rural population. Globally, the level of urbanization is expected to rise from 50 per cent in 2009 to 69 per cent in 2050.

As cities and towns grow, their demand for water increases too which creates a need to make more water available. Therefore water scarcity and the inability to develop resources and systems sufficiently and quickly are becoming increasing constraints to urban development.

As water demand grows, water scarcity is becoming an increasing constraint to urban water management in many settings. Increasingly, sustainable water management requires cities to plan with the whole river- basin in mind. Lack of treatment of city wastes results in increasingly polluted water bodies downstream. This results in environmental degradation, higher costs in water treatment and negatively affects public health and welfare, agriculture and the prospects of exports.

Cities of the future offer the opportunity for integrated urban management. For water management, this could mean adoption of more efficient water treatment technologies, increased re-use of water and wastes, better optimization of the interdependency between water and power generation and improved demand management.

Future urban environments can take better advantage of economies of scale and scope (thereby increasing efficiency and promoting equity through lower costs of provision), reduce the costs of water provision, improve access to services in adjacent rural areas, design sustainable tariff and subsidy schemes and minimize environmental and downstream pollution.

These tasks need to be given more priority because all of society will benefit significantly.