Tech solutions to the water crisis

When most people think of tech solutions to the water crisis, they tend to think of one thing: desalination. It’s tempting to look at the ocean – which, after all, accounts for 70% of our planet’s surface – and think, “we can we just take the salt out and drink that”. The technology exists, and many countries do precisely that. But the bad news is, it’s only a suitable solution for a minority of cases/countries, and it comes at a great cost both economically and environmentally.

Israel for example has solved its water crisis largely through desalination, with over 30 desalination plants, treating around 1 million cubic metres m3 of water every day, providing 85–90% of water supply. But Israel benefits from being a small, wealthy, high-tech country with a coastline spanning its length. That doesn’t describe most countries. Neighbouring Jordan, where I visited for my book The Last Drop, only has a tiny sliver of Red Sea coastline far away from its major cities. It is currently building a large desalination plant, but the water will have to be pumped hundreds of kilometres uphill, becoming far too costly for either bill payers or the government. I much the same in Ghana, too. Even without long-distance pumping, the energy needed to push seawater through the reverse osmosis membranes is huge and typically requires a wealthy, oil-rich government (see UAE or Qatar) to subsidise it. 

Then there’s the waste. In most desalination processes, for every litre of potable water produced, a further 1.5 L of waste brine is created. There is no environmentally sustainable way of disposing of it, so it’s just chucked back out to sea. The result? The Persian Gulf, surrounded by the mega desalination plants of Saudi Arabia, Qatar and the UAE, is now reportedly ‘25% saltier than average seawater’. The saltier it becomes, the harder (ie. more energy intensive) it is to desalinate, becoming more and more expensive. And, of course, sea life dies out. A desalinated world, with dead oceans and unaffordable water, is no utopia.

Intriguingly however, there may be desalination technology around the corner that solves many of these problems. California-based OceanWell is studying the feasibility of harvesting drinking water from desalination pods placed on the deep ocean floor, several miles off the coast. This would use the deep-sea water pressure above to ‘naturally’ push the water through the reverse osmosis membranes – thus halving the associated energy costs. OceanWell claims the natural pressure from the ocean can reduce waste brine to just 10% to 15% of every litre produced. Several water districts in California have already expressed an interest, with one – Las Virgenes Municipal Water District – already participating in a feasibility study.

An emerging off-grid tech solution – and the opposite of the big, centralised municipal solutions – is water-from-air technology. The ones pictured below aren’t solar PV panels, but solar ‘hydro panels’. By creating an artificial dew point inside they can condense and capture moisture in the air. This particular company, Source, based in Arizona, believe these offer a decentralised future of water supply. Each panel only produces around 3 litres a day, though, so this is only really for drinking water. But for off-grid and remote communities, it is a handy renewable resource. A primary school in Maharashtra, India, for example, has six hydro panels, producing some 162,000 litres of clean drinking water for its pupils.

Then there’s the tech we can get within our own homes. An ordinary shower, depending on water pressure, can use around 12-15 litres per minute. If you take a 5 minute shower, that’s 53-75 litres of drinking-quality water down the drain. The Danish designed Flow Loop shower, by contrast, uses just 1–2 litres per minute. It does so by capturing the water from the shower floor as it passes through the plug hole, passes it through a filter and a UV system, and seamlessly recirculates it back to your head. Now your 5 minute shower barely passes the 10 litre mark.

A Netherlands start-up called Hydraloop has created a similar water recycling system for the entire house – taking your used grey water (ie. from your bath, shower, and washing – but not the toilet), cleaning it, and sending it back into the household pipes for a second use. The company claims that the system could reduce a household’s water use by 75,000 L a year. One customer, David Mertens, who lives with his two children in Grimbergen, Belgium, claims that his household (combined, by the way, with a rainwater harvesting tank, as is mandatory in Flanders) now requires only 13 L of mains water per person, per day. Bear in mind that the EU average us 120 L per day, and the UK is closer to 150 L.

The smartest tech solution of all, however, may be to solve the water crisis and the energy crisis at the same time. Irrigation canals lose a lot of water to evaporation, while solar panels are more efficient if cooled from below. India therefore began shading canals with solar panels in Gujarat as far back as 2012. Land is also expensive in India, meaning that these linear solar farms could be put up with no extra land-purchasing cost. In 2019, the Narmada Main Canal was given the green light to fit a full 40-km section, producing 100 MW of electricity – the same as the gas-based power station in Sepahijala District, Tripura. California and Arizona are now following suit, albeit tentatively.

Whole reservoirs can be fitted with floating solar panels, too. China, as ever, can lay claim to the world’s largest floating solar array: on the surface of a reservoir near the city of Huainan, installed in 2017, are some 166,000 floating panels, producing a combined 40 MW. A 2018 World Bank report estimated the global potential for floating solar arrays on man-made reservoirs could exceed 400 GWh. That means that floating PV on dammed reservoirs could exceed the energy output of the hydro-dams themselves. If just 6 per cent of Lake Mead were covered in solar panels, for example, it could theoretically produce 3,400 MW – considerably more than the Hoover Dam’s 2,074 MW.

But most tech solutions are much more mundane. Agriculture accounts for 70% of water use globally. But in the UK, the biggest water user, at just over 50%, is households. And we could all easily use less water. My dishwasher is nothing fancy, but it has an eco-mode that only uses 6.5 litres for an entire cycle. A typical kitchen tap runs at 12 litres a minute – so washing in an economical dishwater compared to under a running tap saves lots of water. As for the taps and shower head – you can fit aerators to them, cheap little discs like the one in the picture below, which can reduce the water coming out of it by half. And a garden water butt or two should replace any need to use a garden hose to water plants. Those three measures, plus fixing a leaky loo, reduced my own household water consumption by almost half.

As for the source of all that water, nature provides the answer. The answer is no longer huge, centralised reservoirs, far away from populations. We need infrastructure that works with and restores natural systems, with wetlands and reedbeds, rather than giant concrete bowls. California is now looking at nature restoration – not tech – as the front line of solving its water crisis. As the LA Times reports, “Throughout the Central Valley, California’s rivers have long been held within their banks by levees and berms, artificially disrupting the natural cycles of flooding and preventing streams from meandering across the landscape… Today, an effort to bring back some of those floodplains is flourishing.” One such project at the 2,100-acre Dos Rios Ranch Preserve work is estimated to save some 1.7million cubic metres for the natural environment and groundwater aquifers – the source of much of California’s drinking water. There is a place for new tech solutions. But we should never forget that the originator of our water system, and its best steward, is nature itself.