The heavy rains that have lashed the UAE over several days this week could offer benefits to a country where the normally arid climate makes it difficult to provide enough water.
A growing population, expansion of urban areas, agriculture, landscaping and industry all put the country’s water resources under strain.
In the coming days at least, wadis are likely to top up aquifers, the underground water-containing rocks that provide much of the UAE’s supply.
“Our monitoring points are indicating that there’s a lot of enhancement in the water level and the quality in some running areas in wadis in the Northern Emirates, also in the Al Ain area. We are expecting a good recharge to the aquifer system in these areas,” said Dr Mohamed Dawoud, a senior water adviser at the Environment Agency – Abu Dhabi (EAD).
Other analysts, including Inesaf Benzaki, a regional campaigner with Greenpeace Mena, emphasise that this week’s rains “can overrun collection infrastructure, and are not a viable or reliable recharge source for long-term water strategies”.
One monitoring station in Ajman recorded 93.3mm of rainfall in only a day earlier this week – about what is expected in a year.
Such rainfall events are unusual but not unheard of, according to Dr Diana Francis, head of the Environmental and Geophysical Sciences (Engeos) Laboratory at Khalifa University in Abu Dhabi.
“It sits in the category of rare, high-impact events,” she said. “Statistically that’s typically a one-in-10 to one-in-50-year event where in places like Abu Dhabi the average annual rainfall is 75mm to 100mm and most rain comes from a handful of winter systems like we are seeing.”
Intensity on the rise
Climate change means that the atmosphere holds more moisture, and there is greater evaporation from the oceans and seas, so intense rainfall over shorter periods is increasingly common even if total rainfall does not increase.
But for the most part, the UAE has a dry climate, putting restrictions on how much freshwater is available.
“Rainfall is extremely low and highly irregular, while evaporation rates are very high. There are no permanent rivers, and natural freshwater resources are limited to shallow aquifers that accumulated thousands of years ago,” Prof Nidal Hilal, director of the Water Research Centre at New York University Abu Dhabi, said of the UAE and other GCC nations. While there are constraints on supply, demand is high.
In the GCC, urban per capita water consumption is more than 500 litres per day, said Dr Nasser Karami, a water scientist and head of the policy council at Mena ERA, an organisation supporting societies in the Mena region facing environmental damage, climate change and land degradation. This compares to 372 litres per day in the US, according to the US Environmental Protection Agency.
Groundwater reserves provide around half the water used in the UAE (desalination accounts for about 40 per cent and treated wastewater 10 per cent), causing aquifers to become depleted.
Ms Benzaki said that shallow aquifers in the GCC have an estimated storage of 131 billion cubic metres (BCM), but receive just 3.5 BCM of annual recharge, while deep fossil aquifers store around 2,175 BCM with recharge of only 2.7 BCM.
“The exploitation rates average five to 10 times the recharge rates in conservative assessments,” she added.
“This has caused a significant decline in groundwater levels, abandonment of production wells, dryness of springs and acceleration of seawater intrusion into coastal aquifers (salinisation).”
The salt concentration in some aquifers is more than 15,000 or 20,000 parts per million (ppm), Dr Dawoud said, compared to less than 1,000 ppm typically for fresh water. Seawater has a salt concentration of about 35,000 ppm
“The drop in water table is more than five metres per year or six metres, which means the pumping is very expensive and costly and the water quality is not suitable for agriculture or for potable water use,” he added.
Keeping crisis at bay
According to Dr Karami, two things have prevented water scarcity in the GCC from turning into “a visible crisis”.
“First, most of the population is not dependent on agriculture and livestock. Second, cheap energy has made large-scale desalination possible,” he said.
Small-scale desalination machines were introduced to Abu Dhabi in the 1960s, but it was not until the following decade that the technology began to be used on a significant scale in the Gulf.
According to the Pulitzer Centre in the US, GCC plants that use water from the Arabian Gulf or the Arabian Sea now account for 31 per cent of global desalination capacity.
There is an continuing transition, Dr Dawoud said, from thermal desalination, in which heat evaporates seawater, to reverse osmosis, a membrane-based approach with lower capital and operational costs but high electricity needs.
Although desalination accounts for less than half of total water use in the UAE, it provides most drinking water.
To reduce pressure on desalination, Dr Karami recommends four approaches: reinvesting in floodwater storage and artificial groundwater recharge; reusing more treated wastewater for agriculture and industry; lowering consumption and reforming water pricing; and reducing water losses from distribution networks.
Making most of rainfall
These are among the measures being taken by the UAE authorities. Prof Hilal said that the UAE had invested heavily in infrastructure to capture and store rainwater, so more rain from extreme events could be captured.
This infrastructure includes recharge dams, retention basins and aquifer recharge systems, which channel stormwater into underground reserves. In this way, Dr Hilal said, the UAE can turn episodic rainfall “into a strategic resource”.
“Over the longer term, although rainfall alone will not fundamentally change overall water availability, the UAE’s proactive and forward-looking water management approach means that even infrequent storms can contribute meaningfully to resilience and long-term water security,” he said.
There are now more than 150 dams and other water barriers in the UAE with a capacity, according to EAD, of around 90 million cubic metres.
These are concentrated in the Northern Emirates, as the mountainous terrain means creates more wadis to channel water. Most of the UAE is flat and surface water accumulation is limited.
In another initiative, Abu Dhabi aims by the end of this year to reuse 100 per cent of wastewater, while the UAE’s Water Security Strategy 2036 targets 95 per cent reuse of treated water.
“Now we are assessing with the municipalities if we can collect the stormwater … in the cities,” Dr Dawoud said.
“It could be treated and recycled or reused. The project is not implemented; it’s just a study now.”
To limit demand, EAD is working with organisations such as Abu Dhabi Agriculture and Food Safety Authority, Abu Dhabi Department of Energy and municipalities to promote irrigation and household technologies that reduce water use.
“In the domestic sector we have the saving faucets to improve the flow and use less water – it’s a mixture between water and air – and also the new plumbing code to help minimise seepage and losses from the distribution networks and the collection networks. All this will help us to improve the situation,” Dr Dawoud said.
Additional measures being employed to reduce demand include, Ms Benzaki highlighted, adjustments to tariffs.
But she warned that population growth, coupled with climate change, which she said would decrease rainfall in the GCC by 10 to 20 per cent by 2050, would put further stress on water supplies.
“This has a direct effect on agriculture and water availability … not only does reduced rainfall volume impact direct supplies, but heat further depletes it by increasing evapotranspiration and decreasing soil moisture,” she said.
So while this week’s heavy rains have topped up the UAE’s store of water, long-term challenges remain.
