The main objective of artificial recharge is to store excess water in underground aquifers during times of surplus that can be recovered during periods of water scarcity. Hence, artificial recharge can be compared to “water banking” and is often also referred to as “Aquifer Storage and Recovery (ASR)”. Significant amounts of water can be stored in the subsurface through the implementation of large schemes, thus avoiding the need to construct large and expensive surface reservoirs and dams and reducing evaporation.
The augmentation of groundwater resources is accomplished through facilities and structures designed to enhance the natural replenishment or increase the infiltration of surface water into the aquifers. For shallow aquifers, this is often done with the help of infiltration ponds or surface runoff diversion structures. Deeper aquifers are usually recharged through injection wells.
Issues to consider
Before implementation, detailed feasibility studies have to be conducted to ensure suitability of the aquifer and optimal design of the required surface installations. In addition, legal, economic, and environmental factors need to be considered for site selection and weighed against alternative options. This includes public acceptance and distance to the point of water use.
- No large structures (dams) needed to store large volumes of water
- Stored water is relatively well protected from evaporation and pollutants
- Schemes can be implemented incrementally, keeping initial capital investment relatively low
- Depleted aquifers can be restored and saltwater intrusion can be controlled by applying artificial recharge
- Purification and improvement of water quality by infiltration and percolation of surface water through the soil
- Minimal land use for water storage required
- Cost-effective implementation and environmental friendliness in comparison with surface storage and dams
- Detailed feasibility studies required before implementation of large schemes
- Continuous maintenance and qualified staff required in order to avoid clogging of injection wells and infiltration ponds, and prevent contamination of groundwater
- Regulatory constraints: compliance of artificial recharge with the country’s water and environmental legislation
- Recovery of stored water requires wells and pumping (energy demand)
- Undesirable chemical reactions can mobilize harmful substances
IWMI (2012): Re-Thinking Water Storage for Climate Change Adaptation in Sub-Saharan Africa. Final Report.