Balancing Human and Ecosystem Needs for Water in Urban Water Supply Planning

Worldwide population and water use trends indicate that management of water ­supplies for urban areas will be a critical issue in the twenty-first century. Between 2005 and 2050, global population is expected to increase from 6.5 billion to over 9.2 billion, with population living in urban areas increasing from 3.2 billion to 6.4 billion (UN 2006; 2007). Such population growth will place increasing pressure on available water supplies for cities, as will water demands for industrial production associated with economic development. Current predictions of global non-agricultural water demands indicate a continuing uptrend in withdrawals, assuming continuation of existing consumption patterns (Rosegrant et al. 2002; Shen et al. 2008; 2030 Water Resources Group 2009). Given that 90% of the 3.2 billion person increase in urban populations by 2050 will be in developing countries (UN 2007), clearly there will be immense pressure to build additional infrastructure to supply water for cities over the next 40 years in the developing world.