As cities grow, technology could help quench the world's thirst
Applying known technologies and changing old practices could make a big difference in ensuring an adequate water supply for both agriculture and cities, one expert says.
London — As competition for water increases, the world’s fast-growing cities will demand an ever larger share – and should be able to afford to pay for it, says Colin Chartres, director general of the International Water Management Institute, based in Sri Lanka.
But that bigger urban share will come at the expense of agricultural water, leaving farmers – today the largest users of freshwater worldwide – trying to grow much more food to meet rising population growth and expanding appetites, all with less water.
Technology and changing old practices could make a difference, says Chartres, noting that capturing and saving water and reducing waste – both on the farm and in cities – could help ensure there is enough to go around.
Q: How do you see growing water scarcity reshaping the world by 2050?
A: Many countries now have about 70 percent or more of their water going to agriculture. In the countries where there’s a lot of population growth and economic growth, there’s going to be a real increase in demand for water from growing urban communities and from industries.
I think what we will be seeing as we go beyond 2030 to 2050 is an increasing number of countries or river basins where the total demand for water exceeds supply. That’s already predicted in India by McKinsey by 2030.
Growing industrial and urban demand and increasing clout of cities means water will be taken away from agriculture. It will be bought or taken by the larger economic power of the cities and the voters in those cities. That means agriculture has to produce food for another 2 billion people by 2050 with the same or less water. We don’t think it’s impossible but it’s going to be tough.
Q: What can be done to make agriculture more productive with less water?
A: A number of things stand out. There are already a lot of technologies available – but not adopted – that can improve crop and water productivity. They range from current and future improvements in seeds and cultivars, including for drought resistance, through to very simple on-farm water productivity improvement measures: better cultivation, better mulching, more efficient irrigation, much less wastage of water. In rain-fed areas where there is no irrigation, you have to consider whether you can supplement rainfall with tube-well irrigation or water harvesting.
Q: Could cities wasting less water help too?
A: If we look at the big cities, we have to make sure they capture as much of their waste water and waste sewage as possible and reuse it in agricultural production. Lot of water goes to cooling for thermal power stations, and most of that goes back into the environment as hot warm water that can be re-used.
Q: Are there any countries addressing these water shortage problems in particularly interesting or effective ways?
India is pretty much aware of its problem and has a number of plans. One has been a very grandiose plan called the national river- linking program, which ties some water in wetter regions to dryer regions by physical structures. It’s extremely expensive and environmentally not necessarily the best way to go.
Another scheme is called Jyotigram Yojana – “lighted village” –- which one of our researchers suggested to the Gujarat government as a low-hanging-fruit solution. Many Indian states subsidize electric power. Because of that many farmers moved to groundwater irrigation – they sink a tube well and attach an electric pump to it. Because electricity is cheap they pump massively and there’s tremendous overuse of groundwater.
There was a close look at this in Gujarat and one idea on how to deal with it was to physically separate the power lines to the irrigation pumps from those going to the towns. It cost $300 million to $400 million to do it. But once they had done it, they could turn off the supply to the pumps for half or two-thirds of the day (and not turn off electricity to the town).
Agricultural production has not suffered at all as a result of that reduction of power. Farmers are able to pump enough in the time the power is on, which has had tremendous benefits. The water table has stopped falling as much. The state has saved hundreds of millions of dollars on subsidized power, and saved greenhouse gas emissions.
And lastly, something we hadn’t thought of happened – ancillary benefits for villages and towns. Without so much demand, the power supply was more constant, and they had far fewer blackouts.
Q: Do you see any particularly interesting efforts to capture and store waste?
A: There’s work on artificially recharging groundwater. A good example of the potential of this is in Uzbekistan, in the Ferghana Valley. There is a lot of water released out of Kyrgyzstan in winter from hydropower plants. That water in the past just ran down the river out into artificial wetlands. It was an absolute waste of water.
But there’s tremendous potential in some of the aquifers in the valley to store that water. We’re looking at how much they could capture and infiltrate back. They would have to pump it out in summer, which would take some power, but it’s better than letting it be lost.
In Thailand there’s some blue-sky thinking – how they could capture a lot of the runoff that caused terrible flooding in Bangkok, capture it upstream and put it into aquifers and use for agriculture? That’s very experimental but there’s a lot of interest around the world.
It all comes back to simple solutions – the technology is there.
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