Rain harvesting could help Dubai offset a stormy future

Reuters

• Reuse of water is essential
• ‘Sponge City’ scheme planned
• Developers already harvest rain

If last week’s floods made improving drainage a necessity for Dubai, the reward might come in the form of more natural water resources, provided the emirate can boost rain harvesting efforts, industry observers tell AGBI.

“The main idea for countries, especially in drier areas, is to try to reuse water as much as possible,” says Ronny Berndtsson, water resources engineering professor at the Centre for Advanced Middle Eastern Studies at Lund University in Sweden.

UAE sustainability company Dake Rechsand says it can help municipalities to retrofit roads, sidewalks and other surfaces with permeable materials. Rainwater can thus seep into the ground and flow into decentralised storage tanks that keep it clean without electricity or chemicals. 

Chandra Dake, the company’s founder, tells AGBI he is in talks with the Dubai government to implement two “Sponge City” pilot projects.

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“A sponge has two functions: it can absorb water … and then you can squeeze it in a bucket,” Dake says.

“That’s exactly what our system does. Every drop of water which falls on it can be absorbed and then that water can be taken and used for cleaning the roads or irrigating the plants.” 

Approximate calculations suggest each millimetre of rain produces one litre of water for each square metre of a building’s roof.

The National Centre of Meteorology says the country’s hardest-hit areas recorded upwards of 254mm of rain during the storm’s 24 hours – more than the national average annual rainfall of 140 to 200mm.

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A study by researchers at the NCM published in the journal Nature in January predicts the UAE will experience increases in mean annual rainfall of 15 to 30 percent this century.

As part of larger water-management efforts, Dubai real estate development and hospitality company Five Holdings has embraced rainwater harvesting.

Director of sustainability David Shepley says that at its Jumeirah Village location, a catchment basin on the roof and fifth floor podium connects a line to the hotel’s greywater system. At Five Palm Jumeirah, meanwhile, it captures rainwater from a basin in the parking area.

“The rainwater harvesting lines integrate with our greywater recovery networks, which service the hotel’s irrigation and cleaning operation,” says Shepley.

He tells AGBI the Five Jumeirah Village system captured 185,000 litres of water during the storm, while Five Palm Jumeirah recovered 390,000 litres.

“This puts into perspective both the severity of the climate event and the impact of having a system in place to capitalise on the water collection opportunity, especially in the UAE’s water stressed region.”

While rainfall in Dubai and the UAE is set to increase in the coming decades, it is unlikely to become on par with that of non-desert countries.

That raises the question of whether investments in rainwater harvesting makes business sense here.

“Yes, it is worth it,” says Shepley. “The marginal investment needed to install a rainwater connection line outweighs the potential of the loss of water or its devastating effects.”

On Wednesday the UAE government announced it would allocate AED 2 billion ($544 million) towards fixing up damaged homes. In the immediate aftermath of the storm, President Sheikh Mohamed bin Zayed Al Nahyan ordered a review of infrastructure nationwide.