Managed Aquifer Recharge in the Middle East: What Comes Back

Managed aquifer recharge is offered to the Middle East as the answer to three water problems at once: the desalinated water a plant produces in winter and cannot sell, the treated effluent with no other outlet, and the flood that runs to the sea in a few hours. The region has built accordingly, from a strategic reserve of desalinated water beneath the Liwa dunes to hundreds of recharge dams across the Peninsula and decades of effluent recharge on the Mediterranean coast. Each programme is described by its builders in terms of capacity and intent. A scheme is judged by two other numbers: the fraction of the water applied that comes back, and the cost of each cubic metre that does.

Geologic® put that question to the published record and counted the answer. From a documented search of 2,918 records screened twice and 131 full texts read in full, every value was extracted with its page and a verbatim quotation and sorted into three tiers by the basis of its numbers: an operating record, measured or estimated from operation, a design or model output, and a partition with no returned volume. The returned fraction can be computed for 33 scheme-source pairs, and for only 14 of them from an operating record, covering 9 schemes in 5 countries across the Middle East and its arid margins. Recovery to use and infiltration are kept apart throughout, at operating-record medians, per scheme, of 0.72 and 0.49, because they are different quantities and pooling them produces a number that describes nothing. The Gulf strategic reserve has no published full-scale recovery: its pilot covered 70 days of pumping against 250 of infiltration and returned 0.28. These are the figures a decision between a recharge scheme and another desalination plant actually turns on, and the review ends with the four things a scheme must publish for its return to be computable at all.