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Droughts are classified as the most expensive climate disasters as they leave long-term and chronic impacts on the ecosystem, agriculture, and human society. The intensity, frequency, and duration of drought events have increased in the past and are expected to continue rising at global, continental, and regional scales. Nature-based solutions (NBS) are highlighted as effective solutions to cope with the future impacts of these events. Despite this, there has been limited comprehensive research on the effectiveness of NBS for drought mitigation, and existing suitability mapping frameworks often overlook drought-specific criteria. To address this gap, a new framework is proposed to identify areas suitable for two drought-coping NBS types at a regional scale: detention basins and managed aquifer recharge. Two multi-criteria decision-making techniques (MCDM), i.e. Boolean logic and Analytic- Hierarchy Process (AHP), were used to map suitable large-scale NBS. The new framework accounts for unique criteria to specifically address drought conditions. By incorporating climate change scenarios for both surface and groundwater, recharge, and different groundwater characteristics, it identifies suitable and sustainable locations capable of managing extreme drought events. Executed through Boolean logic at a regional scale in Flanders (Belgium), the framework's strict approach yields significant potential areas for detention basins (298.7 km²) and managed aquifer recharge (867.5 km²). Incorporating AHP with the same criteria introduces a higher degree of flexibility for decision-makers. This approach shows a notable expansion across Flanders, varying with the level of suitability. The results underscore the highly suitable potential for detention basins (2552.2 km²) and managed aquifer recharge (2538.7 km²), emphasizing the adaptability and scalability of the framework for addressing drought in the region. The comparison between potential recharge volume due to detention basin and groundwater use in the region indicated that the detention basins could partially compensate for the high water demand. Therefore, creating a framework targeting drought is vital for the sustainable management of water scarcity scenarios., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Estifanos Addisu Yimer reports financial support was provided by Research Foundation Flanders (FWO, PhD grant no. 1S11022N). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The Intermunicipal Water Company of Veurne-Ambacht (IWVA) started reusing wastewater effluent for infiltration in its dune water catchment, St-André, in 2002. The treatment train at the Water Production Centre Torreele is based on a multiple-barrier approach with submerged ultrafiltration prior to reverse osmosis. The project improved the ecological values of the dunes. Recently, during longer periods of drought, the combination of reuse and managed aquifer recharge proved more robust than conventional drinking water production sites: groundwater levels at St-André remained high enough to ensure drinking water production and protect its quality. IWVA's experience shows that water reuse can help mitigate the impact of climate change. [ABSTRACT FROM AUTHOR]

The Torreele facility produces infiltration water for indirect potable re-use through artificial recharge of the dune aquifer of St-André. The secondary wastewater effluent is treated by ultrafiltration (UF), using the submerged Zeeweed system, prior to reverse osmosis (RO), using brackish water low energy membranes. The Torreele experience showed that combining UF and RO enables the treatment of wastewater effluent in an effective and reliable way; RO being the major and ultimate barrier against both microbial and chemical contamination. The produced filtrate is of excellent quality and enables sustainable groundwater management in an area with high ecological interest. The biggest challenges for the Torreele facility are the changing conditions, based on the meteorological and seasonal variations, the scaling and fouling problem and the concentrate. Bio-fouling is prevented by monochloramination and scaling by dosing of antiscalant combined with pH adjustment. The Intermunicipal Water Company of the Furnes Region (IWVA) studied alternative treatment, mainly using natural systems, with the objective to mitigate the impact of the concentrate disposal into surface water and to reduce the charges set for this disposal. Concerning groundwater recharge, IWVA is studying alternatives to optimize the infiltration capacity. [ABSTRACT FROM AUTHOR]