Tuesday, April 19, 2011

Urbanization, Climate Change and Water

By 2050 there will be an additional 3 billion urban dwellers. Cities, especially in developing countries will struggle with three main issues regarding water namely; quality, quantity and delivery. In addition to the challenge of providing adequate water to urban residents owing to population growth, cities and their neighborhoods will face unprecedented hydrologic changes. In a paper published in PNAS, (April 12, 2011), McDonald et al. use a detailed hydrologic model, demographic projections, and climate change scenarios to estimate per-capita water availability for major cities in the developing world, where urban populations are growing rapidly. Their results show that currently 150 million people live in cities with perennial water shortage. Water shortage is defined here as having less than 100 litres of water per person per day, a rough measure of the amount an urban resident needs in a sanitary manner over the long-term. This includes water for cleaning, bathing, flush toilets as well as drinking.

According to McDonald and colleagues, demographic growth will increase the number of urban residents having less than 100 litres of water per day to 1 billion by 2050. Climate change will cause water shortage for an additional 100 million urbanites. More importantly, the study suggests that freshwater ecosystems in river basins with large populations of urbanites with insufficient water will likely experience flows insufficient to maintain ecological process. Cities will struggle to find enough water for the needs of their residents and will need significant investment if they are to secure adequate water supplies and safeguard functioning freshwater ecosystems for future generations.

The authors conclude that urban growth–water conundrum is solvable. But it will take money, time, political will, and effective governance. Countries with moderate to high per-capita income seem more likely to find adequate solutions to urban water problems with domestic investments, if sufficient political will is found. However, countries with low per-capita income will external financing and commitments by the international community.

See full article: www.pnas.org/cgi/doi/10.1073/pnas.1011615108

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