Editor’s pickAs the global population continues to boom, big cities are heading towards a water crisis

08-03-2018

For the very first time in history, more than half the global population is residing in metropolises – with the number expected to rise to two-thirds.

But with this number comes more sombre news: In 2010, more than 30 per cent of cities were already vulnerable to water shortages and drought. And by 2040, more than 40 per cent of cities in the world that draw their water from inadequate surface sources could find themselves vulnerable, according to a new research study.

Cities usually spring up near a supply of water, and as the population expands, so does the demand for the resource, according to Eco-Business. But although the demand rises, the supply remains constant.

A number of cities are already suffering under drought stress – In India, Chennai needed water to be supplied through tankers in 2004 and 2005, and São Paulo, Brazil, is just about at its crisis point.

 

The seen threat

Julie Padowski, an environmental scientist, and Steven Gorelick, director of the Global Freshwater Initiative at Stanford University, California, United States (U.S.), wrote in Environmental Research Letters that they surveyed 70 cities sprawled across 39 countries with more than 750,000 residents each and dependent on surface water for their supply.

Of the cities they analysed, they found that 44 per cent were vulnerable as found by calculating the demand and supply. And this number does not factor in the impacts of climate change, which will likely worsen the situation.

But the cities that are already considered vulnerable are heavily reliant on reservoirs, which, in turn, need to be recharged, or urban planners would need to begin thinking about adding more reservoirs, deepening wells, building desalination and water recycling plants, or diverting a river to act as a new source of water supply.

 

The unseen threat

Patrick Reed, professor of civil and environmental engineering at Cornell University and his colleagues stated in the Environmental Research Letters that the network of satellites dedicated to predicting rainfall data “fails to meet operational data needs for flood management”, with four of the ten satellites having surpassed their shelf life and the satellites designed to monitor rainfall and flooding coming to the end of their lifespans as well.

The instruments based in space offer scientists and authorities a method of keeping an eye on rainfall and ground moisture in such a way that there is time to forecast moments when rivers rise and overwhelm cities, flooding them. But already, weak spots in the network have begun to appear, especially in developing nations, meaning that floods have the potential to catch people off-guard. When the four satellites fail, the potential for a disaster will increase.

“It is important for us to start thinking as a globe about a serious discussion on flood adaptation and aiding affected populations to reduce their risks,” Professor Reed said. “We want to give people time to evacuate, to make better choices, and to understand their conditions.”

 

Source: Eco-Business