Tuesday, June 19, 2018

Water - too little - too much

Currently, 844 million people – about one in nine of the planet’s population – lack access to clean, affordable water within half an hour of their homes, and every year nearly 300,000 children under five die of diarrhoea, linked to dirty water and poor sanitation. 

It would cost just 0.1% of global GDP, to provide water and hygiene to all those who need it.

Climate change is bringing droughts and heatwaves across the globe, as well as floods and sea level rises. Pollution is growing, both of freshwater supplies and underground aquifers. The depletion of those aquifers can also make the remaining water more saline. Fertilisers leaching nitrates into the supplies can also make water unsuitable for drinking or irrigation.

The poor are worst hit. Jonathan Farr, senior policy analyst at WaterAid, says: “Competing demands for water means that those who are poorer or marginalised find it more difficult to get water than the rich and powerful.” Many governments and privatised water companies concentrate their provision on wealthy districts, and prioritise agriculture and industry over poorer people, while turning a blind eye to polluters and those who over-extract water from underground sources.

Data from the Nasa Grace – Gravity Recovery and Climate Experiment – satellites over a 14-year period discovered 19 hotspots around the world where water resources are being rapidly depleted, with potentially disastrous results. They include areas of California, north-western China, northern and eastern India, and the Middle East. Overall, as climate change scientists had predicted, areas of the world already prone to drought were found to be getting drier, and areas that were already wet getting wetter. According to James Famiglietti, co-author of the Nasa Grace study, some of the areas most vulnerable are “already past sustainability tipping points” as their major aquifers are being rapidly depleted, in particular the Arabian peninsula, the north China plain, the Ogallala aquifer under the great plains of the US, the Guarani aquifer in south America, the north-west Sahara aquifer system and others. “When those aquifers can no longer supply water – and some, like the southern half of the Ogallala, may run out by 2050 – where will we be producing our food and where will the water come from?” he asks.

There is no global management system for water. Water is managed at a local level, and often poorly managed. The technology needed to help us use water efficiently and equitably exists, but often is not implemented. “In many instances, proper management of known technology [such as pumps, rainwater collectors, storage cisterns and latrines] rather than new technological solutions is sufficient to ensure users receive adequate services,” says Jonathan Farr, senior policy analyst at WaterAid. “We have been solving the problem of getting access to water resources since civilisation began. We know how to do it. We just need to manage it.” He notes, in many remote parts of sub-Saharan Africa, “there may be sufficient supplies of groundwater but there has not been enough investment in service delivery and service management to ensure that people can access this water”.

Some of the most effective ways of managing water resources are also the simplest. Plugging leaks in pipes is a good example – ageing or poorly maintained infrastructure wastes vast quantities of water. A dripping tap can leak 300 litres a year. In the UK, the Environment Agency has warned of water shortages across the south-east of the country within a few years, if the 3bn litres a day wasted through leaks – enough for the needs of 20 million people – continues.

 Irrigation has enabled farmers even in arid regions to grow a wider variety of crops. Some methods of irrigation are highly inefficient – in hot countries, water sprayed on crops evaporates before it can reach the roots. An alternative is drip irrigation, a system of pipes that delivers water directly to the roots of each plant, but this is also prone to wastage. Marc Stutter, of the James Hutton Institute explains that in Rajasthan, in India, restoring traditional small dams called johads enabled the periodic rains to be held before they dissipated across the land. The johads led to “the miraculous revitalisation to a green landscape and the surface water returning”.

Advances in sensor technology offer a new way forward. Field sensors, available for as little as $2 a year, can monitor the moisture content in soil, letting farmers know whether irrigation is needed and allowing them to calibrate the irrigation more finely than has previously been possible.
Science is also being brought to bear on the crops themselves. Plant biologists are breeding varieties less prone to drought, through natural selection, and in some cases using genetic modification. But science and technology can only go so far. As with most water issues, the biggest problem is still that farmers will grow what they can to turn a profit, and many have little alternative than to use scarce groundwater resources. How do you fit 130 litres of water in a single cup? The answer: fill it with coffee. Growing coffee beans is a thirsty business, as is growing cotton – 10,000 litres of water in a pair of jeans – and 2,500 litres in the average T-shirt. Avocados, almonds – even bottles of water themselves, are all highly water-intensive enterprises. Agriculture uses about 70% of freshwater across the globe. Vincent Casey, senior manager at WaterAid. “It doesn’t make sense for Saudi Arabia to use vast quantities of limited water resources for agriculture when food grown elsewhere can be imported.”
Climate change will not only mean more droughts, but also more frequent floods. These can be devastating to agriculture and cities, especially coastal cities already under threat from rising sea levels and stronger storm surges. The World Bank estimates that the damage to cities from flooding will top $1 trillion by 2050 if strong action is not taken to equip cities to cope with the consequences. In tropical areas more than a fifth of the mangrove swamps that used to cling to the coastline have been destroyed, cut down to make way for agriculture and aquaculture. Restoring mangroves yields many benefits: they protect inland areas from sea level rises and storm flooding, and provide nurseries for fish, increasing fishing yields. Flood plains and water meadows also provide natural water storage, with land that acts like a sponge to soak up water, releasing it gradually over time. This can prove unpopular with farmers who want to grow crops on such land, but payments from the public purse can offset the cost to them. 
he planet’s biggest water resource, seawater, is in no danger of running out, making up 97% of Earth’s water. Why not harness it for drinking?
The most basic technology to do so has been in use for nearly as long as fire: distillation, the process of boiling water and catching the steam, condensing it into liquid. In small quantities, this can be done easily, and cleanses water of other impurities as well as salt. But at large scale, such as providing the drinking water needs for a city, the process is fuel-intensive, even using modern methods such as low-pressure vessels to lower the boiling point.
Alternative technologies use electrical currents, which when passed through the water can separate out salt and other minerals, and reverse osmosis, by which saline water is passed at high pressure through membranes that exclude salt and impurities. Both these methods also have high energy requirements, which makes them costly, and adds to global greenhouse gas emissions. Sucking in seawater can also suck in fish and damage coastal ecosystems. Waste from the plants is another issue: the salty residue is usually released back into the sea, but this must be carefully managed because at the concentrations produced it is toxic to marine life.
Energy costs have proved prohibitively high for most countries, so the main users of desalination to date have been among the fuel-rich and arid countries of the Middle East. However, the water crisis has gripped so hard in some areas of the world that some cities see little alternative. Cape Town’s first desalination plant has just started operating, after some severe budget woes. China, Pakistan and India are exploring new desalination plants. If renewable energy can be used to power the plants, this should reduce the impact on climate change.
Floating houses are another idea that is taking off, from the Netherlands to south-east Asia. The houses are built on floating platforms instead of foundations, but anchored to the sea or river bed, and a wide variety of modern designs are now available. Sea level rise driven by climate change is set to pose an existential crisis to many US coastal communities, with new research finding that as many as 311,000 homes face being flooded every two weeks within the next 30 years. Philip Stoddard, the mayor of South Miami. “People on the waterfront won’t be able to stay unless they are very wealthy. This isn’t a risk, it’s inevitable."

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