Like other Arabian Gulf states, the UAE has long faced water scarcity, and this problem intensifies as growth and development continue.
World Water Day on Wednesday turned the global spotlight on the precious resource, and this is good news because the UAE has one of the highest per-capita water consumption figures in the world despite having limited water resources and modest rainfall.
One study puts it at 550 litres per day, compared with the global average of about 200 litres.
About 51 per cent of the UAE’s water supply comes from groundwater and demand is such that a UAE University report in 2015 warned that the country’s water supplies could be depleted within the next few decades.
It is vital to ensure that as much as possible of the rain that falls replenishes water supplies, as there is a need to improve the natural renewal of groundwater resources.
Dr Mohsen Sherif, director of the National Water Centre at UAE University in Al Ain, has dedicated the past 15 years to understanding this issue.
He and his team have been looking at the efficiency with which rainfall enters the system of aquifers, the water-containing rocks that lie underground. Several factors are at play.
If the aquifer is “unconfined”, then water can seep into it directly from above, but other aquifers, described as confined, cannot so easily be reached because there is an impermeable layer between the ground surface and the aquifer.
In most of the UAE, there is no layer of clay to prevent water from infiltrating the surficial (near to the Earth’s surface) aquifers.
The time of the year at which rain falls is also important.
“Usually the rainfall in the UAE will happen from November to March, during which time the evaporation is relatively low,” said Dr Sherif.
The UAE is, however, warm and sunny year-round, and losses from evaporation are part of the reason that little more than 10 per cent of rainfall ends up replenishing aquifers in some areas.
The use of groundwater-refilling dams to create lakes and ponds has, in many places, dramatically increased the efficiency of replenishment, to the extent that in their vicinity most of the rainfall can find its way into the vital underground water reserves.
“In some cases, from heavy rainfall, the water will be in the ponding areas of the dams for one month or two months. A significant amount will recharge the groundwater system,” said Dr Sherif.
“Part of it will evaporate. Eventually, all the water will evaporate or infiltrate. During the winter, the infiltration [into an aquifer] may reach 35 per cent of the accumulated water in the pond itself, sometimes 40 per cent. This is, relatively, very high.” Other water collected by dams ends up in the unsaturated zone, an area that lies below the surface of the Earth but above the aquifers. An additional 30 per cent of the water in pools may eventually find its way into the unsaturated zone, increasing the soil moisture content and allowing natural habitats to flourish, something that can often be seen in the vicinity of dams after heavy rainfall.
Added together, this means that nearly three-quarters of the water in the ponding areas of dams can replenish the UAE’s underwater reserves, thanks to the groundwater-refilling dams.
“The total infiltration reaching the unsaturated and saturated zones may reach 70 per cent, 72 per cent in the ponding areas of the dams. In the other areas, the recharge may not exceed 12 per cent depending on the topographical conditions, land cover, temperature and others,” said Dr Sherif. The UAE has more than 110 dams and, although found in many parts of the country, they are concentrated in the Northern Emirates, especially Ras Al Khaimah and Fujairah, where the terrain is ideal, rainfall tends to be higher and significant amounts of water run-off can be collected.
“They’ve been constructed over the past 35 years. Some of the dams were constructed in the 1980s. They are very effective at recharging groundwater,” said Dr Sherif.
Among the locations where dams can be found are Wadi Al Baih in Ras Al Khaimah and Wadi Ham in Fujairah.
Despite the effort that the UAE has made to build dams, renewable water resources are continuing to be depleted because of what Dr Sherif describes as the excessive pumping of water for agriculture. Also, the UAE’s average yearly rainfall has declined considerably and, since 1998, has been significantly below the long-term average of 110 millimetres per year, said Dr Sherif, possibly because of climate change. In some areas, the water table has fallen tens of metres over the past decades.
“The rainfall is very limited. The consumption is higher than the recharge from the rainfall and the region is arid. There’s not enough rainfall,” he said.
“Specifically for the agriculture, I think there’s a need to make a little bit of conservation because the agricultural sector is consuming the majority of the groundwater resources.”
Other factors, such as reducing wastage from water-conveying systems, can also help.
“In the past, there was really no control of the consumption. Now the Environment Agency Abu Dhabi is implementing measures to control the pumping of groundwater, so now it’s better,” said Dr Sherif, whose research is carried out in cooperation with ministries and authorities.
“The survey project of all groundwater wells will be completed by the end of 2017. The use of groundwater has declined compared with the past.”
The data on how much rainfall replenishes aquifers is helpful because it can indicate how much water can be extracted in a sustainable manner.
“Sustainability of water, and specifically groundwater resources, is very important for the continuation of the current economic development and prosperity of the nation,” said Dr Sherif.
To help the authorities, maps showing yearly rainfall across the UAE have been produced by the National Water Centre. This can help to indicate where development should take place.
So, in the face of severe challenges, much is being done to ensure that water supplies are conserved for future generations.
newsdesk@thenational.ae
