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MAR suitability mapping

MAR suitability mapping

A visual tool to raise awareness on the potential of MAR

The potential of regional mapping of suitability to Managed Aquifer Recharge (MAR) using a standardized index was investigated during a 4-months internship project by Fanny Dupont. Continuing the work of INOWAS (TU Dresden), the potential of the MAR Site Selection Standardization Index (MARSSSI) to map the suitability to spreading methods was investigated with a new case study. 

Subsequently, an index based on a similar methodology was developed to assess the regional suitability not only to spreading methods but also to other MAR techniques. It is recognized that regional MAR suitability maps based on few criteria are of limited use for building new MAR sites without further site-specific investigation including e.g. the objectives of MAR, the source of water and the budget available. These maps must be seen as MAR intrinsic suitability maps. However, they can raise awareness among policy-makers on the wide applicability of MAR as a water management solution in a context of global changes.

Study area, methodology and results

The Occitanie region in southern France was selected for this study. It appeared as an interesting area for MAR suitability due to its diversity of geomorphology, current challenges for water management and the presence of 9 MAR sites. In the first project stage, a suitability map for MAR spreading methods was created and compared to a map resulting from the application of MARSSSI. 

Based on a literature review of MAR suitability mapping and the knowledge of the study area, the suitability to MAR spreading methods in Occitanie was assessed using 6 criteria: terrain slope, hydrogeology (4 sub-criteria describing the nature of hydrogeological entity, type of porosity, level of confinement and type of geological formations), distance to source water, soil texture, land cover, potential to reduce nitrate concentrations in surface water. The criteria included in MARSSSI are the terrain slope, geology (hydrogeological context) and soil texture. With a good reproduction of highly suitable areas, MARSSSI gave promising results to map the regional suitability to the application of MAR spreading methods using a reference index. 

In the second stage of the project work, a new methodology of MAR intrinsic suitability mapping was developed that include other types of MAR techniques in the suitability analysis. Indeed, it was observed in literature that most studies are restricted to only one type of MAR techniques but presenting the results as ‘MAR suitability’, creating a confusion and underestimation of the potential of MAR. This new methodology is based on several criteria classified as ‘Favourable’ or ‘Unfavourable’ to the various MAR techniques. It was applied to the Occitanie region. It showed that 65% of the Occitanie is potentially suitable for the application of at least one MAR technique, with areas ranked favourable to up to 6 types of techniques.

Main outcomes for MAR suitability mapping

Based on physiographic properties of the study area, MARSSSI does not include specific considerations of a potential new MAR site but reflects the intrinsic suitability of a study area to spreading methods. A new intrinsic suitability index was developed to include all MAR techniques, demonstrating the wide applicability of MAR over a given region. This new methodology could be replicated in other parts of the world to raise awareness on the potential of MAR for water resources management.

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