Banking water underground: the region's other reservoirs

Every surface reservoir in a hot climate loses water to the sky. The oldest answer is also a growing procurement category: put the water underground. Managed aquifer recharge now stores an estimated 10 cubic kilometres a year worldwide. That is about 2.4% of groundwater extraction in the countries that report it, and roughly 1% globally.¹

Recharge has grown about 5% a year since the 1960s without keeping pace with pumping. Its reviewers expect it to exceed 10% of global extraction, on the evidence of the places where it is most advanced.¹

Three tools, one idea

The simplest is the recharge dam, a low structure across a wadi that holds a flash flood long enough for it to soak into the gravel. Infiltration basins spread treated wastewater or surplus water over sand and let the soil polish it on the way down. Aquifer storage and recovery wells skip the surface, injecting treated water into the formation and pumping it back later.

The region already uses all three. IGRAC’s global inventory lists 176 recharge records across the Arab states and Israel, led by Egypt, Oman and Tunisia, plus 53 in Iran.²

Records are sites or case studies and include pilots, so the count measures activity rather than stored volume.²

Oman’s dams

Oman has made recharge a national infrastructure class. It has 212 dams with about 458.8 million cubic metres of storage, including 53 groundwater recharge dams holding 108.6 million.³ Its storage and recharge dams had impounded more than 3.17 billion cubic metres of floodwater by the end of 2025.⁴ Recharge efficiency has been measured at up to 75% in Dhofar.⁵ A further 33 dams, recharge structures among them, are planned under the Eleventh Five-Year Development Plan.³

The insurance policy in the dunes

The reference project is in the Liwa desert. Desalination makes water continuously, so a city whose plants stop depends on what it has stored. Environment Agency Abu Dhabi first investigated the idea in 2002, and the reserve was built with the Abu Dhabi Water and Electricity Authority and its TRANSCO subsidiary.⁶ It holds more than 26 million cubic metres of desalinated water in a dune aquifer, enough for 90 days of emergency supply to the emirate.⁷ Some 315 wells give a fallback pumping capacity of 100 million gallons a day.⁶

The numbers deserve care. Reported cost is US$435 million in one account and US$350 million in another.⁶⁷ A recovery efficiency of 88% is widely quoted.⁸ What is documented is the pilot, where recovery worked, and no published account covers a full-scale recovery cycle.⁷

Recharge with treated effluent

Israel runs the region’s largest example. The Shafdan plant treats about 140 million cubic metres of wastewater a year from Tel Aviv and seven neighbouring towns. The effluent filters through sand in recharge basins and is recovered from surrounding wells 6 to 12 months later. In dry months Mekorot pumps more than 130 million cubic metres of it to the Negev, treated to a standard that allows unrestricted irrigation.⁹¹⁰

Elsewhere the schemes are smaller. Bahrain has recharged the Khobar aquifer with treated effluent since 1986.¹¹ Oman injects treated wastewater at Salalah, where it pushed the saline front back from 3.4 to 2.7 km.⁵⁸ The approach is also easier to explain in public, because the water comes back out of the ground rather than straight from a treatment works.

The honest limits

Recharge stores water; it does not create any. Some of what goes down mixes with brackish water or moves away, recovery is never complete, and wells need a regime for managing clogging.¹ Kuwait shows how long the road from design to scheme can be. A 2013 design study modelled 100,000 cubic metres a day of recovery from eight wells at Kabd, and a 2022 modelling paper still described the reserve as planned.⁸¹⁴

Where the market is

Hydrogeologists get paid before contractors do. Modelling, pilot wells and monitoring networks decide feasibility, and the drilling and instrumentation follow. National strategies carry recharge lines that have not yet become tenders. Saudi Arabia’s National Water Strategy lists recharge and underground storage as an initiative, with a target of 100,000 cubic metres a day at the Abar Al Mashi well field.¹⁵ Morocco shows why a target needs a date and a source. Its national water strategy aimed at 270 million cubic metres a year by 2030, while a 2018 government presentation cited a potential of 180 million.¹⁶¹⁷

In the region

Recharge and strategic storage run through the projects register. The Shafdan plant is the reuse reference, and Qatar’s mega-reservoirs show the surface alternative. In Qatar, peer-reviewed siting work has identified zones that could hold up to 182.8 million cubic metres if a recharge scheme were built.¹³ Tunisia recharged 20 of 28 targeted aquifers with 38.4 million cubic metres in 2011, 92% of it from hill dams.¹²

The case study

One scheme in this sector, examined in full: what was built, what it cost, what worked and what did not.

Who is doing this

The buyers and operators behind the procurements this brief describes.

• Environment Agency – Abu Dhabi (EAD)Environment · United Arab Emirates
• Ministry of Agriculture, Fisheries & Water ResourcesBasin & resources authority · Oman
• MekorotBulk producer · Israel
• Ministry of Environment, Water & Agriculture (MEWA)Ministry · Saudi Arabia

Mandates, procurement routes and the rest of the region’s institutions are in the decision-maker directory.

What to watch

• Q1 2028Completion of Oman’s Lima Dam, the one dated milestone reported among 33 new dams planned under the Eleventh Five-Year Development Plan.³
• PendingSaudi Arabia’s Abar Al Mashi injection scheme, targeting 100,000 m³ a day into 400 million m³ of available storage.¹⁵

Further reading

• Dillon, P. et al. (2019), “Sixty years of global progress in managed aquifer recharge”, Hydrogeology Journal. The first global estimate of how much water is banked underground. doi.org
• Parimalarenganayaki, S. (2020), “Managed aquifer recharge in the Gulf countries: a review and selection criteria”. The Gulf schemes compared, with their numbers. pmc.ncbi.nlm.nih.gov
• GRIPP and IWMI, “A strategic water reserve in Abu Dhabi” (2018). The Liwa scheme described by the agency that conceived it. gripp.iwmi.org
• World Bank (2017), Water management in Israel. How Shafdan’s soil-aquifer treatment feeds the Negev. documents1.worldbank.org
• IGRAC Global MAR Portal. Every inventoried recharge scheme on one map. ggis.un-igrac.org