There are different terms to describe the intentional infiltration of available surface water into the aquifer. These are, for example: Groundwater recharge, Artificial infiltration of groundwater, and Managed Aquifer Recharge (MAR). The process is used to increase the natural yield of the aquifer, and to improve the quality of the infiltrated water.
There are just few basic requirements that are needed for successful implementation of groundwater recharge:
- Source of raw water for infiltration
- Suitable target aquifer
- Application of suitable techniques for infiltration and recovery of water
In most European cases, especially in Northern and Central Europe, the artificial infiltration of groundwater is used for drinking water production. In some other cases, the method is applied to produce irrigation water for agriculture.
However, the successful implementation of aquifer recharge requires a lot of expertise and data from the raw water conditions and hydrogeological and geochemical conditions of the target aquifer. Knowledge of the aquifer properties is essential in the designing of suitable infiltration and recovery techniques, because this process harnesses the physical, chemical, and biological interactions that occur during the extended residence time of infiltrated water within the aquifer.
In addition, the requirements of the amount and quality of the data increase when the objectives and goals for artificial infiltration become more demanding.
Groundwater recharge can be utilized in different geological environments and climatic conditions. It is a globally applicable method as presented in the UNESCO publication Managing Aquifer Recharge (2021). Based on the case studies and applications around the world, artificial infiltration of groundwater can be described as a safe, sustainable and cost-efficient method to produce drinking water.
The technique is:
Cost-efficient technology for water supply
- It is a natural method with minor chemical use.
- It is easily automated and remotely controlled process.
- The method provides the water producer with a large sub-surface storage capacity, which also increases the resilience of the production system.
Sustainable way of managing water resources
- It provides adaptation tools for climate change in both increasing or decreasing precipitation.
- It can be used to restore and expand the existing aquifer capacity.
Safe solution for several common challenges
- Raising or stabilizing groundwater levels in the aquifer
- Preventing saline intrusion or land subsidence caused by excessive groundwater pumping
- It provides tools to manage stormwater runoff and floods
The forementioned objectives and goals can be achieved with a highly sophisticated Managed Aquifer Recharge system. As one might assume, that level can’t always be achieved. Shortcomings, for example, caused by the lack of raw water or wrong infiltration techniques can lead to issues with too low water production rates. Also, inadequate and insufficiently mapped geochemical conditions of the target aquifer or too short residence times of the infiltrated water can lead to water quality issues.
Therefore, more attention should be focused on mapping and modelling of the internal structures and properties of the aquifers. For example, 3D hydrogeological models can be applied to understand and depict the 3D hydrogeological structures of the aquifer. This architectural data of the aquifer can be further adopted to build more precise groundwater flow models to calculate and simulate the aquifer volumes, flow paths and residence times of the infiltrated water.
Failures to obtain water production goals might occur if they do not coincide with the natural capabilities and/or quality restraints of the aquifer to produce needed amounts of artificially infiltrated groundwater. Therefore, the mentioned modelling tools are vital both in planning and in the production phase of the Managed Aquifer Recharge project. An example of the project in which all these requirements have been met is the water production system built by Turku Region Water Ltd. The company built a MAR based system in the esker aquifer that meets the needs of the whole Turku region with more than 300,000 inhabitants and industry.
In the case of Turku Region Water Ltd., the application of MAR method has allowed more than 10 times bigger production rates as compared with naturally formed groundwater without any unwanted changes in groundwater quality. As a matter of fact, the company has restored the groundwater levels and spring discharge rates to a level that occurred in the aquifer prior to any groundwater intake.
Therefore, Turku Region Water’s MAR system has gained excellent Sustainability Index ratings presented in the MAR publication by UNESCO in 2021.
Reference:
UNESCO, Zheng et al. (2021) https://unesdoc.unesco.org/ark:/48223/pf0000379962
Aki Artimo
CEO
Turku Region Water Ltd.
Finland
