Aquifer Storage and Recovery for Demand Levelling — Riyadh

## Background Riyadh's treated water demand peaks sharply in June–August, requiring desalination plants to run at or above nameplate capacity. The National Water Company sought a buffer that could absorb off-peak production and release it during peak periods. ## Challenge The local aquifer is brackish (TDS 1,800–2,400 mg/L) and heterogeneous. Injected treated water must be recovered with quality ≥ potable standards without excessive blending. ## Approach A three-well ASR pilot was constructed with a 500 m³/h injection capacity. Recovery was managed through a blending ratio model that ensured TDS at the wellhead stayed below 500 mg/L. Cycle testing over two years refined the injection-storage-recovery sequence. ## Results - 4.2 million m³ stored and recovered in Year 2 pilot - Peak-day desalination plant load reduced by 12 % - Recovered water TDS consistently below 480 mg/L - Unit cost of stored water: USD 0.09/m³ vs. USD 0.31/m³ for incremental SWRO capacity