Political agreement on water rights and usage should be at the heart of climate-change conference discussions (see http://www.nature.com/roadtocopenhagen). Policy-makers, whose real agenda may be their standing with their electorates, should recognize that water is an ideal vehicle for reaching a useful aggregate agreement.

Water is where the impact of human-induced climate change is felt most keenly at a regional level. Demand is increasing, and the economic and social costs of extreme events such as floods and droughts are high. We should be ready to invest more in agricultural and industrial water-use efficiency, as well as in regional adaptation measures — bearing in mind that both water transport and desalination are very energy-intensive processes.

Globally, more than 32 trillion litres of treated water leak from urban water supply systems every year, according to the energy and water department of the World Bank (see http://go.nature.com/fLFTId). Last year, the UK water-industry regulator Ofwat reported that 22% of the water supply for England and Wales leaked away — 3.3 billion litres a day (see http://go.nature.com/3hJC7f). In developing countries, 40–50% of the supply may be lost this way.

The World Bank expects adaptation to climate change to cost US$75–100 billion a year until 2050 in developing countries alone (see http://go.nature.com/JCqkYq). The question of how to finance this is on the Copenhagen agenda.

One of the key requirements for success is to link incentives for sustainable water management with adaptation and mitigation strategies at a local scale. Local voters and governments are concerned with economic development, which is strongly linked to the security of water supplies, and are therefore most likely to support such measures.