Managed Aquifer Recharge (MAR)

Managed aquifer recharge (MAR) involves building infrastructure and/or modifying the landscape to intentionally enhance groundwater recharge.

MAR is among the most significant adaptation opportunities for developing countries seeking to reduce vulnerability to climate change and hydrological variability. It has several potential benefits, including: storing water for future use, stabilizing or recovering groundwater levels in over-exploited aquifers, reducing evaporative losses, managing saline intrusion or land subsidence, and enabling reuse of waste or storm water.

Implementation of MAR requires suitable groundwater storage opportunities. Falling water levels or pressures in aquifers in many regions throughout the world are creating such opportunities, either as unsaturated conditions in unconfined aquifers or as a pressure reduction in confined aquifers. However, MAR is not a remedy for water scarcity in all areas. Aquifer conditions must be appropriate and suitable water sources (e.g. excess wet season surface water flows or treated waste water) are also required. MAR potential should be determined in any particular country or region before activities commence.

Construction, operations and maintenance

MAR methods may be grouped into the following broad approaches (Figure 3.5):

• Spreading methods – such as infiltration ponds, soil-aquifer treatment, in which overland flows are dispersed to encourage groundwater recharge;
• In-channel modifications – such as percolation ponds, sand dams, subsurface dams, leaky dams and recharge releases, in which direct river channel modifications are made to increase recharge;
• Wells, shafts, and boreholes recharge – in which infrastructure are developed to pump water to an aquifer to recharge it and then either withdraw it at the same or a nearby location (e.g. aquifer storage and recovery, ASR);
• Induced bank infiltration – in which groundwater is withdrawn at one location to create or enhance a hydraulic gradient that will lead to increased recharge (e.g. bank filtration, dune filtration)
• Rainwater harvesting – in which rainfall onto hard surfaces (e.g. building roofs, paved car parks) is captured in above or below ground tanks and then allowed to slowly infiltrate into soil.