Abu Dhabi has unveiled the world’s largest reserve of high quality desalinated water, secured in a network of 315 recovery wells lying up to 80 m below the Liwa Desert.
The wells are fed by one of the UAE's longest water pipeline networks which runs the water from Shuweihat desalination plant at a rate of 7 million imperial gallons (approx. 32,000 cu m) / day over 27 months.
The reserve, which has at its core an infiltration and recovery system sitting atop a natural freshwater underground aquifer, was first investigated in 2002 and has been extensively researched by the Environment Agency - Abu Dhabi (EAD). The project was undertaken as a collaborative venture between EAD, delivering the vital scientific studies, feasibility, risk and mitigation scenarios as well as strategic planning Abu Dhabi Water and Electricity Authority (Adwea) and its Transco subsidiary, which managed the construction and on-the-ground implementation.
Dr Saif Saleh Al Seairi, acting director general of Adwea, said: “The reserve acts as a safety net for the provision of water and is now being regarded as an excellent regional model for foresight and planning.”
“We applaud the efforts of the team that worked hard in some of the harshest desert conditions and in an environment of a constantly undulating landscape. The project team overcame considerable challenges to complete this one-of-a-kind scheme and lessons learned have been shared with our regional partners. This project has positioned Abu Dhabi,” he added.
“The entire project is a testament to the power of multi-stakeholder collaboration and an exemplary case study in inter-governmental cooperation driven by environmental pillars guiding sustainable economic imperatives,” said Razan Khalifa Al Mubarak, secretary general, EAD.
The project has addressed Abu Dhabi’s water security and its resilience through the recharge of groundwater aquifers with high-quality desalinated water, which cannot be stored above ground due to contamination and other factors. The desalinated water is piped from the coast to create the secure, underground reserve system and was accomplished by a multi-national and multi-disciplinary team of experts from EAD, Transco, Adwea, RSB, the independent regulatory body for Abu Dhabi’s water and electricity sector, GIZ International, Do. Rainer Consultancy and ACC-Posco JV.
Established in one of the world’s driest areas where rainfall rarely exceeds 10 cm a year, the project has been completed at an estimated cost of Dh1.61 billion ($435.616 million) to deliver a fallback pumping capacity of 100 million gallons of water/day to the emirate if required. The desalinated water percolates into the subsurface through basins with a system of semi-perforated underground pipes to recharge the aquifer using only gravity as a driving force.
The project ensures continuous water supply for Abu Dhabi city and Al Dhafra region and secures the reserve for future generations. Whenever needed, water from the 315 wells, lying up to 80 metres below ground, can be used to recover supplies at any time.
The reserve now holds more than 26 million cu m of water (equivalent to 5.6 billion imperial gallons) that can bolster drinking water supply when needed. “Long-term wellbeing of our communities is enhanced by the maintenance and enhancement of groundwater while being conscious that we need to progress additional recharge and recovery projects to optimize the flexible allocation of water as required,” said Razan Al Mubarak.
Throughout the implementation of the project, considerable attention was paid to the use of highly engineered, environment-friendly specification materials, which were deemed appropriate to the Liwa area. The infiltration basin was insulated with protective materials, including a gravel mix of large pore stones to evenly distribute water and ensure better filtration.
The 160-km pipeline from the strategic water reserve site to the Madinat Zayed distribution network in Abu Dhabi city consists of approximately 9,000 sections of welded pipes some of which measure 1.2 m in diameter, and are up to 18 m long. The sections had to be transported into the desert and pieced together through high precision welding which would take up to five continuous hours per section with stringent, follow-on X-ray inspection to ensure the system was leak-proof and could withstand the prevailing water pressure for a minimum of 50 years.
Concerns about aquifer contamination from large animals, such as roaming camels, were addressed by working with nature which resulted in the creation of a ‘groundwater protection buffer zone’ made from locally produced palm-frond while solar panels power wellhead monitoring instrumentation, the statement said.
Reallocating the surplus from desalinated water into the reserve addresses some of the challenges brought by dependence on desalination plants. “Desalination plants can be shut down by storms, a malfunction, a random sea raft and even the red tide phenomenon which has been exacerbated by climate change and negatively impacts water quality, the environment and ultimately the local economy. We need strategic reserves in the event of one or more stations being out of service and we need to ensure the availability of an alternative so that the population, industrial and commercial sectors are not negatively affected. The government realised the need for an alternative supply to cover our needs in the near or far term, and one which would also mitigate against climate risks and it is wisely investing in finding solutions” stated Al Seairi.
The Liwa desert was chosen for the project after it met strict specification criteria. These included an extremely light water basin trajectory to prevent leakage; capable of sustaining a ‘tank’ thickness to handle significant storage volumes; safe surroundings free of human activities which could contaminate the reserve and where groundwater quality was of sufficient quality to allow for ‘recharge and mixing.’
“We decided to recharge the depleting ground aquifers with our surplus desalinated water and the result proved to be the most efficient way to store water at the lowest cost,” explained Al Seairi. “We do not need to build and maintain water tanks. We do not need energy to power their injection. We only re-inject water to replenish and restore what was previously there.”
Water quality is ensured through strict control, heat and salinity monitoring equipment and a range of other metrics. “Running the expansive well network simultaneously is a complex process. Communication and inter-team information exchange is critical. All this data is connected to a master network that acts as the project’s ‘brain’ and is housed in a state-of-the-art electronic process centre from which technicians control pumps, wells and valves and water quality which complies with RSB drinking water standards, is ensured by automatically operating at least 20 wells per day,” stated Al Seairi.
Following the signing of a Memorandum of Understanding between EAD, represented by Razan Al Mubarak and Transco, represented by Mohammed bin Omair Al Shamsi, chairman, at the International Water Summit, being held as part of the Abu Dhabi Sustainability Week, the strategic water reserve project will now be operated, managed and maintained by Transco with scientific support by EAD.