Managed aquifer recharge (MAR) is the purposeful recharge of an aquifer for later recovery or environmental benefits and represents a valuable method for sustainable water resources management. Models can be helpful tools for the assessment of MAR systems. This review encompasses a survey and an analysis of case studies which apply flow and transport models to evaluate MAR. The observed modeling objectives include the planning or optimization of MAR schemes as well as the identification and quantification of geochemical processes during injection, storage and recovery. The water recovery efficiency and the impact of the injected water on the ambient groundwater are further objectives investigated in the reviewed studies. These objectives are mainly solved by using groundwater flow models. Unsaturated flow models, solute transport models, reactive geochemical models as well as water balance models are also frequently applied and often coupled. As each planning step to setup a new MAR facility requires cost and time investment, modeling is used to minimize hazard risks and assess possible constraints of the system such as low recovery efficiency, clogging and geochemical processes.

Managed aquifer recharge (MAR) is being successfully implemented worldwide for various purposes: to increase groundwater storage, improve water quality, restore groundwater levels, prevent salt water intrusion, manage water distribution systems, and enhance ecological benefits. To better understand the role of MAR in sustainable water management and adaptation to climate and land use change, about 1200 case studies from 62 countries were collected and analyzed with respect to historical development, site characterization, operational scheme, objectives and methods used, as well as quantitative and qualitative characterization of in- and outflow of water. The data harvested was used for the compilation of a global inventory of MAR schemes, whose main goal is to provide access to existing MAR projects and techniques and demonstrate their benefits. To increase the availability and facilitate continuous update of the MAR inventory, an MAR web-based portal was developed and integrated into IGRAC’s Global Groundwater Information System. The MAR portal contains a “data layer catalog” containing the data arranged in a systematic way, a “map viewer” to visualize the selected data on a geographic location, and a “features panel” providing tabular output of the selected data. By facilitating access and promoting international sharing of information and knowledge on MAR, the web-based MAR portal aims to increase awareness of MAR as a viable solution for sustainable groundwater resources development and management, and to provide a new tool for better planning of MAR at regional and global scale.

Suitability maps for managed aquifer recharge (MAR) sites hold a strong potential for integration into sustainable groundwater management plans. An uprising method to identify sites suitable for MAR implementation is geographic information system (GIS)-based multi-criteria decision analysis (MCDA). There are no guidelines or a common understanding on how suitability mapping should be conducted, and there is considerable variability as to what factors are assessed and how they are weighted. To increase knowledge on GIS-MCDA, a database has been built based on 63 studies applying GIS-MCDA in the context of MAR site selection. Information on the criteria, assigned weights, and methodologies has been retrieved from the documents. Statistical analysis of the database depicts the current state of art for suitability mapping methodologies as well as specific information for the different recharge methods. We further incorporated the compiled information into a web-based query tool that makes the information easily accessible and the utilization of the database more user friendly. This review as well as the created web-tool will help planners of MAR sites to engage in the MCDA in a more structured way by referring to previously conducted studies and by finding information suitable for their specific project. The application potential of suitability maps is discussed along with the shortcomings of this methodology.

Costa Rica’s annual mean precipitation is above 3300 mm, but this precipitation is not evenly distributed in time or space, producing clear differentiated wet and dry seasons in most of the country. Droughts are also common phenomena which greatly affect the availability of water resources. Managed aquifer recharge (MAR) schemes are being taken into consideration to enhance the underground water storage capacity of the country. The present study constitutes the first assessment for the identification of suitable sites for the implementation of MAR technology spreading methods (SM) in Costa Rica. The suitable sites are identified by means of a geographic information system multi-criteria decision analysis (GIS-MCDA) based on four criteria: hydrogeological aptitude, terrain slope, top soil texture and drainage network density. Four steps are performed in order to identify these sites: problem definition, screening for suitable areas, suitability mapping, and sensitivity analysis. The suitability map was divided in two zones after the screening: suitable and unsuitable, the first zone was further divided in five classes according to the weighted linear combination (WLC) ranking. The results indicate that 61% of the country is suitable for conducting SM. This map is a tool for future implementation of MAR techniques in the country.

Sustained environmental and human health protection is threatened by ~350,000 chemicals available in global markets, plus new biological entities including coronaviruses. These water-quality hazards challenge the proponents of managed aquifer recharge (MAR) who seek to ensure the integrity of groundwater. A risk-based regulatory framework accounting for groundwater quality changes, adoption in subsurface attenuation zones, and use of advanced monitoring methods is required to support confidence in the sustainability of MAR.

Soil aquifer treatment (SAT) is a nature-inspired solution for improving the water quality through soil percolation. The biodegradation of organic matter typically occurs in the shallowest soil layer and it depends on the contaminant’s characteristics (water solubility, molecular structure) and specific soil properties (pore size distribution). The present study aims at identifying which grain size fraction of typically used sandy soils in the shallowest layer of SAT systems can provide the optimal conditions for microbiological growth that can be reached by a trade-off between soil moisture as well as nutrients and oxygen supply. For this, soil columns were used at a laboratory scale to determine the relationship between the pore size distribution of four different grain size fractions and biodegradation rates of organic matter from synthetic wastewater. The results obtained from this experimental setup indicate that bacterial colonies reached optimum growth when about 60% of the available pore space was filled with water. For the selected soil, this was achieved by the fraction with grain sizes in the range of 630 µm to 1000 µm, having pore diameters between 87 µm and 320 µm and a mean pore diameter of 230 µm.