Managed aquifer recharge is the deliberate adding of water to an aquifer for later use or for environmental benefit.
Managed aquifer recharge, or MAR, means intentionally adding water to an aquifer so that it can be recovered later or can support the environment. It stores water underground, where it does not evaporate and needs no new reservoir. Common methods include infiltration ponds and basins, check dams and percolation tanks on seasonal streams, recharge wells and shafts, and aquifer storage and recovery, in which the same well is used to inject and later pump water. Riverbank filtration and soil aquifer treatment also use the ground to improve water quality. Source water may be monsoon runoff, river floodwater, stormwater, or highly treated wastewater. The choice of site depends on having permeable ground, enough storage space above the water table, a reliable source and a way to get the water back. The main technical problem is clogging by silt, algae and bacteria, so basins are scraped and wells redeveloped. Water quality also needs checking, because mixing can dissolve arsenic or other substances from the aquifer. Measuring recharge properly requires monitoring before and after, since a structure that holds water is not proof that an aquifer has gained it.