Managed Aquifer Recharge (MAR)
Subsurface Storage of Freshwater Resources
Managed Aquifer Recharge, or simply 'MAR,' is a promising sustainable water management strategy. A MAR operation involves placing freshwater in natural aquifers, through infiltration wells, and later recovering that water, through abstraction wells (which are essentially just conventional wells).
Our motivation for implementing MAR is to balance freshwater supply and demand. Practically, this means that during the wet season (in say: The Netherlands, or Florida, or Bangladesh), when there is a surplus of water, we can store the extra water underground for 'safe-keeping,' then during the dry season, when water is scarce, we recover the water by pumping it back out through the abstraction well (or wells).
The schematic above, of a MAR operation in the Netherlands, shows the freshwater filtration through course and fine sand filters. After filtration, the water is pumped into a stand-pipe (quite literally a standing pipe), which uses gravity to infiltrate the water into the aquifer below (the large, light grey area). The freshwater initially mixes with the native groundwater, but this creates a buffer zone that protects the rest of the injected freshwater, which is later pumped out.
Time-Lapse of MAR Infiltration
These images show the evolution of a MAR system over time, as fresh water is injected into the aquifer system. The dark blue is the expanding region of unmixed freshwater, the two lighter blue areas show the mixed water in the buffer zone, beyond the mixing there is native groundwater (in a sandy aquifer).