Managed Aquifer Recharge (MAR)

Perhaps some of you harvest rainwater from roof-tops to irrigate, collect surface runoff water from the hillside, or have drinking water from bank filtration. Previous examples are called managed aquifer recharge – MAR systems.

The MAR technology is based on the aquifers’ artificially inhanced recharge in an eco-friendly way to guarantee groundwater’s appropriate quality, chemical composition and quantity. Surface water, rainwater, or even treated wastewater can be used as recharge water according to the MAR system’s purpose:

• stop water level decrease in arid regions or seasons and have enough water reserve for agriculture and vegetation. Treated wastewater can be used for this purpose;
• store water under the ground which can be more efficient than storing surface water. Groundwater is naturally protected from surface contamination and evaporation loss, so we can preserve more water in a better quality;
• purify water naturally. Some pollutants are stuck during infiltration through the unsaturated zone. Moreover, a thin biofilm with microscopic organisms can also purify water as it takes place on the bed of lakes and rivers and naturally filtrates water that flows to groundwater reservoir;
• improve water quality. If we refill the aquifers with drinking water, we can use it later (for example in times of drought) or we can reach a better chemical composition of water. In coastal areas, managed aquifer recharge can stop seawater to invade the aquifer and make groundwater non-potable;
• preserve groundwater dependent ecosystems and protect biodiversity. This can be beneficial for nature, turism, and culture as well.

Complex hydrogeological and engineering competence is needed to plan MAR systems. Experts must take into account geological conditions, groundwater flow systems, water extraction needs, and recharge water quality and quantity. Moreover, the vulnerability of the aquifer, nearby urban areas, natural and socio-economic benefits must be measured during the planning phase.

Source: https://recharge.iah.org/files/2016/11/MAR_Intro-Waterlines-2009.pdf 

Managed aquifer recharge methods can be divided into two basic groups:

1. to redound infiltration
2. and to facilitate water collection.

In the first group we can find infiltration ponds and basins, flooding, and excess irrigation which can increase groundwater level in a large area. If we have limited area for infiltration, well, shaft and borehole recharge is preferred. We can also mention here the method of induced bank filtration. It consists of wells parallel to the bank of a lake or river. As pumping starts, it induces the surface water to enter the aquifer. The most important advantage of bank filtration is that water is naturally purified during this process by a thin biofilm layer on the bed.

In the second category we can mention recharge dams which collect surface runoff and help infiltration. It’s also efficient to use sand dams in intermittent river beds to store water and reduce evaporation loss. Subsurface dams can be installed as well to prevent horizontal groundwater flow and even contaminant spread. A very easily feasible method is rainwater harvesting when clear rainwater is collected from roof-tops and infiltrated through wells before it could mobilize pollutants from the surface or reach the sewer. It can be useful especially in urban areas.

Managed aquifer recharge methods are such simple but very efficient water management systems which can help us to have clear potable water, to produce food sustainably and to protect the environment. For more information about MARs, we recommend you to visit the global MAR inventory or the website of IAH (International Association of Hydrogeologists) Commission on Managing Aquifer Recharge.