2017年8月18日 星期五

global water crisis: is the world running out of fresh water?

Water crisis⛈


Increasing temperatures and populations threaten a precious element and pose a serious problem. What can we do about protecting our most vital resource?



Given that 70% of the Earth’s surface is water, and that volume remains constant (at 1,386,000,000 cubic kilometres), how is a water shortage even possible?



And both populations and temperatures are ever-rising, meaning that the freshwater we do have is under severe pressure.



Water demand globally is projected to increase by 55% between 2000 and 2050. Much of the demand is driven by agriculture, which accounts for 70% of global freshwater use, and food production will need to grow by 69% by 2035 to feed the growing population. Water withdrawal for energy, used for cooling power stations, is also expected to increase by over 20%. In other words, the near future presents one big freshwater drain after the next.



Of the world’s major aquifers (gravel and sand-filled underground reservoirs), 21 out of 37 are receding, from India and China to the United States and France. The Ganges Basin in India is depleting, due to population and irrigation demands, by an estimated 6.31 centimetres every year. Jay Famiglietti, senior water scientist at Nasa, has warned that “the water table is dropping all over the world. There’s not an infinite supply of water.”



Much of the same is happening in California. From 2011 to 2016, the state suffered its worst drought in 1,200 years. Its major aquifers receded at a combined rate of 16 million acre-feet per year, and roughly 1,900 wells ran dry. Then, in the first three months of 2017, rain fell at 228% more than its normal level, thanks to climate change, scientists say. Lake Oroville in the northern part of the state swung from being at 41% of capacity to 101% in just two months, causing dams to be overwhelmed and 188,000 local residents to be evacuated.



Some hypothesise that increased water shortages around the world will lead to wars. The current Syrian civil war has been cited by many, including Dr Peter Engelke, senior Fellow at Washington-based think tank Atlantic Council, as a recent example. “Between 2007 and 2010, Syria experienced one of the worst droughts in recorded history, the effect of which was to decimate rural communities and drive hundreds of thousands off the land and into Syria’s cities, where they were marginalised," he says.



Anders Berntell, executive director of 2030 Water Resources Group, a multi-sector water resources body, also suggests a link to Boko Haram and Al-Shabaab, whereby young people “realise that, as a result of the lack of natural resources, degraded land and lack of water there are no livelihood opportunities… There is no future for them. They become easily targeted.” They are more easily radicalised.





All of which would predict a bleak future – but some nations have worked out solutions. And they’re impressive ones that the rest of the world can learn from.





For example, Australia survived its “Millennium Drought” from 1997 to 2009 by rapidly implementing measures that halved business and residential water use.



The key was putting a price on water and making it a tradable commodity.

Another ‘gold standard’ is Israel, which views water availability as a national security issue.



By recycling effluent water, including household sewage, the Shafdan Wastewater Treatment Facility near Tel Aviv supplies approximately 140,000,000 cubic metres of water per year for agricultural use, covering 50,000 acres of irrigated land. Over 40% of Israel’s agricultural water needs are now supplied by effluent water. The waste sludge is also sent to an anaerobic digestion plant, which uses the methane as a fuel to produce renewable energy.



Even more mind-blowing? Israel’s water treatment systems recapture 86% of the water that goes down the drain – the next-best performer, Spain, recycles just 19%.



Israel is also a global leader in desalination – turning seawater into potable drinking water. Over half of Israel's drinking water now comes from desalination.



So can the world simply desalinate its way out of the freshwater crisis? It’s unlikely, says Damiane: “On average it's about five to seven times more expensive. The energy footprint is huge, and you've got to do something with the salt. If you look at aerial images around the coasts of Kuwait and Dubai [areas that are highly reliant on desalination] you’ll see the havoc that is caused to marine ecosystems.”

Given the costs, both economic and ecologic, “it is only a boutique solution in very rich places”, he says.



Manchester Metropolitan University’s Birley Campus, built in 2014 to house some 6,500 students and staff, aims to be entirely water self-sufficient through rainwater capture, waste water recycling, and a borehole into the sandstone aquifer below.



In most places around the world the [agriculture] irrigation techniques are pretty inefficient," says Engelke. “Very efficient irrigation techniques do exist. Thermal power sources [nuclear, coal, natural gas] require vast amounts of water for cooling. Renewables for the most part – solar and wind – do not. It all has to do with policies to encourage, incentivise, and invest.”
http://www.bbc.com/future/story/20170412-is-the-world-running-out-of-fresh-water