How much water have you used so far today?
Retrace your steps. What did you first do when you stumbled out of bed? Reach for a sip of water from the glass on your bedside table? Flush the toilet? Make a pot of coffee? Run the dishwasher? Heat up the shower?
How many of our routine tasks of daily living involve water? Very many of them, if you stop to think. What if you had less than a bathtub full of water to accomplish all of your daily needs, from bathing to washing clothes?
That may be the reality facing nearly 1 billion people who live in cities around the world by 2050 if we don’t take steps to manage our water resources now, according to a new study by scientists at The Nature Conservancy and other institutions.
The minimum a person needs is 100 liters (26 gallons) of water a day, or about two-thirds of a bathtub, according to the World Health Organization. Americans use 2 to 5 times as much water per day. (Surely, lingering in a hot shower is one of those wasteful pleasures of which I am guilty.)
Urban growth and climate change are both factors that will push water supplies in some regions to their limits, according to Rob McDonald, co-author with Carmen Revenga of the study Urban growth, climate change, and freshwater availability, published online this week in the journal Proceedings of the National Academy of Sciences (PNAS).
As cities grow due to migration and population growth, the number of city dwellers who have access to less than 100 liters a day of water will increase from 150 million (in 2000) to close to 1 billion by 2050, the study found.
Adding in the effects of climate change on the hydrologic cycle further increases those numbers. While some cities will get wetter and others drier with climate change, the study found that about 100 million additional city dwellers will live with perennial water shortages by 2050 than under current climate conditions.
The cities most likely to be affected include Delhi, Mumbai, Mexico City, Tehran, Manila, Johannesburg and Beijing. The freshwater fish populations and river systems serving large cities with insufficient water supplies are likely to be adversely affected as these cities search further away from their borders for additional surface water or groundwater supplies.
The authors caution that the number of city dwellers to be affected by water shortages is not a prediction, but a warning – a future that can be avoided.
Water conservation and new infrastructure will be needed to avert the scenarios outlined in the study, according to the authors. The location, design and operation of any new dams, canals and reservoirs should take into account ecosystem needs to ensure that we are not jeopardizing the functions that sustain our water sources. Another key step is developing water policies that work with nature, by recognizing the role that upland forests and natural areas play in providing clean water for people who live in the downstream lowlands.
Making investments now to prepare for future conditions, including a changing climate, will be critical to ensuring that people around the world have enough water to drink and to live – one more reason why U.S. investments in international funding to boost climate change resilience should not be eliminated from the federal budget.
I’ll think twice about my “tub full of water” tomorrow.
Also see Robert Lalasz of The Nature Conservancy’s take on these findings in his column for Grist.
Lisa Hayden is climate change writer for The Nature Conservancy
Photo by: Flickr user waterdotorg (A school girl in India drinks water from a new hand pump) Used under a Creative Commons license.
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