They are fixing leaks in Johannesburg, topping up groundwater in Salisbury, Australia, and flushing toilets with sea water in Hong Kong. Municipalities around the world are also adjusting water pressure to minimise loss and make their distribution systems more efficient.
These are just a few examples of how cities are getting smart about managing their water supplies. There are plenty more in a Water Resources Group (WRG) report, which addresses the problem of urban dry out.
The water risks are mounting
The need for action to secure future water supplies is clear enough.
“The issue of water is paramount, and the pressure on cities is increasing,” says Seth Schultz, Director of Research of the C40 Cities Climate Leadership Group, a global network of large and innovative cities taking action to reduce carbon emissions and climate risks.
Among other things, he cites a recent C40 survey of major cities around the world in which 65% of these municipalities are expecting ‘substantive risks’ to their water supplies. These risks include water scarcity, declining water quality, flooding and an inadequate or ageing water infrastructure.
"The issue of water is paramount, and the pressure on cities is increasing."
Seth Schultz, Director of Research, C40 Cities
Copenhagen has almost cut water consumption in half
One city that has successfully met the challenge of diminishing water supplies is Copenhagen. The Danish capital has managed to reduce its yearly water consumption from 100 million m3 in the late 1970s to 55 million m3 today.
“That’s a reduction by almost half,” says Planning Manager Jens Andersen of the Greater Copenhagen Utility Company. Water metering is one of many strategies that has helped the city to reach this remarkable achievement, he notes.
“Without individual water meters, a consumer has no incentive to save. But after we installed meters, we could see over a period of years that consumption was reduced by an average of 15%.”
Leaky pipes cause astonishing water losses
Like many other water-wise cities, Copenhagen has done much to reduce leaks, which can cause astonishing water losses. The WRG describes situations in which 40% or more of the water that is pumped into a distribution grid is lost before it ever reaches the consumer.
“Our leakage losses are now down to just 7%,” says Jens Andersen. “Thanks to some highly advanced listening equipment, we’ve become better at finding the holes in our pipes. We’re also better at renewal planning, so we can prioritise the oldest and most heavily used areas of the grid.”
Water-saving campaigns, rising water prices and a growing awareness of the need for conservation have also helped reduce consumption, he adds. Meanwhile, the city continues to search for new water sources and has entered a water-sharing agreement with the city of Roskilde, 34 kilometres to the west.
‘Smart’ technologies take off the pressure
According to the WRG report, many cities have also found that if they simply reduce water pressure in the grid, they also reduce leakage and minimise wear and tear on aging pipes.
To this end, ‘smart’ technologies such as the Demand Driven Distribution pressure control system developed by Grundfos can save both water and money by delivering optimal water pressure at any given time, says Group Vice President Tao Bindslev, who heads up the company’s Water Utility business.
“This system can automatically monitor grid use patterns with remote sensors and adjust the water pressure accordingly using a Grundfos software algorithm,” he says. “This reduces both water and electricity consumption by up to 20%, and water pipes will last longer because they are less likely to crack.”
The return on investment, says Tao Bindslev, is “very short. In some cases down to a year.”
"Without individual water meters, a consumer has no incentive to save."
Planning Manager Jens Andersen, Greater Copenhagen Utility Company
Saving up for a non-rainy day
Some cities have managed to address two problems at once by harvesting storm water and storing it underground, essentially saving up their water for dry spells.
In the Australian city of Salisbury, for example, storm water is led into an engineered wetland that filters and cleans the water naturally before it is pumped into the aquifer 164 meters underground. From here, the rain water can later be pumped up for irrigation and industrial uses, according to the WRG (Figures 1 and 2).
This solution not only helps prevent flooding, it can also replenish ground water that has become dangerously low in many areas like Salisbury. Compared to storing water in an above-ground reservoir, it also eliminates water loss from evaporation.
Private enterprise has a role to play
Private companies with specialised knowledge such as Grundfos also have a role to play in helping cities overcome their water supply challenges, says Tao Bindslev.
“Collaboration across the value chain is essential to building resilient cities,” he notes. “Grundfos is working with city designers and consultants at every point in the water cycle on creating sustainable urban designs for water management systems.”
Money and ecology are major hurdles
Water-wise solutions abound, but so do the hurdles. Financing large water projects is one of the main issues – not least in developing countries, says Seth Schultz.
“Just collecting information and data on leakage can be difficult and costly in some third world cities, where records are still mostly on paper,” he says. “Unless you have the data, you won’t know that you have, say, a 25% leakage. And if you can’t measure it, you can’t manage it.”
Ecology is also a hurdle. In Copenhagen, for example, Jens Andersen reports that it is becoming more difficult to get permission to drill for water in new areas outside the city. Communities worry about the consequences of removing more and more water from their ecosystems, he says.
There is no ‘distant oasis’
A study by the US environmental group Nature Conservancy is sceptical of expensive water projects.
"Collaboration across the value chain is essential to building resilient cities."
Group Vice President Tao Bindslev, head of Grundfos’ Water Utility business
It contends that cities need to re-think the practice of establishing new water sources in faraway rivers and reservoirs. Ultimately, there is no ‘distant oasis’ that can solve a city’s water problems.
Instead, the study points to conservation as the most sustainable and cost-effective way to address water shortages. One of the most effective ideas of all, the authors argue, would be for municipal water managers to sit down with farmers and work out some mutually beneficial ways to conserve irrigation water. For example, massive amounts of water could be freed up for urban use if cities would compensate farmers for establishing more efficient irrigation technologies such as lined canals and improved delivery systems. The farmers, meanwhile, would benefit from the subsidy and experience increased productivity.
Cities are ready and able to change
Despite the obvious challenges, Seth Schultz is convinced that cities are both willing and able to make the changes that are necessary for a sustainable, water-scarce future. “The good news is that city mayors actually have very strong powers in the water sector, as such cities have the ability to make changes in this area. They are already ramping up their activities dramatically,” he says. “So yes, I’m very optimistic. But I also know how much more needs to happen.”
Story by Anne Nielsen
Photos of Jens Andersen and Tao Bindslev by Christian Andersson
"Unless you have the data, you won’t know that you have, say, a 25% leakage. And if you can’t measure it, you can’t manage it."
Seth Schultz, Director of Research, C40 Cities