By 2025 at least 40 per cent of world’s 7.2 billion people are likely to face serious problems related to freshwater for agriculture, industry or human health. Water management would thus be the key to meet present and future needs with currently available surface and groundwater resources while at the same time preserving terrestrial and aquatic ecosystems. Managed Aquifer Recharge (MAR) refers to intentional storage and treatment of recycled water in aquifers under controlled conditions either for withdrawal at a later date or to be used as a barrier to prevent saltwater or other contaminants from entering the aquifer. The term ‘artificial recharge’ has also been used to describe this activity – which however, has an adverse connotation particularly when community participation is becoming increasingly prevalent in
water resources management. Hence the suggestion for a new name.
Water can be recharged through infiltration by basins, galleries or by use of injection wells. Different types of water can be used as a source of MAR such as captured storm as well as treated wastewater depending upon availability, conditions of the aquifer and the potential uses of recovered water. The different ways in which MAR works are:
- aquifer storage and
recovery (ASR) – injection and recovery of water from the same well;
- aquifer storage, transfer
and recovery (ASTR) – injecting water into a well for storage and recovery from a different well;
- infiltration pond- diverting surface water into off-stream basins and channels that allow water to soak through an unsaturated zone to the underlying unconfined aquifer; and
- recharge via infiltration galleries, soil aquifer treatment (SAT), percolation tanks or recharge weirs and recharge releases etc.
As the treated water infiltrates the soil and aquifer, natural biological, chemical and physical processes take place because of naturally occurring micro-organisms in the aquifer to remove pathogens and chemicals from water. The ability to remove contaminants from water significantly reduces the health and environmental risks that may be associated with secondary treated wastewater.
The main purpose of aquifer recharge is to store excess water for later use, while improving water quality by recharging the aquifer with potable quality water. If the groundwater is saline then recharging it with fresher water will not only displace the saline groundwater, but it can increase water storage in the aquifer. Groundwater recharge may also be used to mitigate or control saltwater intrusion into coastal aquifers. As the per capita water availability of water is rapidly decreasing MAR is the best process that can meet the growing demand and maintain a balance between demand and supply.