Report on Improving Water Quality at Active MAR Sites in Spain
Creators: name: Fernández Escalante, Enrique
name: Henao Casas, Jose David
name: Calero Gil, Rodrigo
name: San Sebastián Sauto, Jon
name: Ayuga, Francisco
name: Behle, Vera Rebecca
name: Sapiano, Manuel
Publisher: name: Zenodo
Year: 2023

description: Managed Aquifer Recharge (MAR) is a promising technique for water management. It comprises a<br> group of technologies that enhance the infiltration of various water sources into aquifers. The water<br> stored underground can serve different uses, such as irrigation, industrial and drinking water supply,<br> and the recovery or preservation of environmental assets. Globally, water resources are increasingly<br> under pressure. MAR offers the potential to buffer water resource availability and meet demands in<br> periods of water scarcity. Consequently, the uptake of this technique will likely soar in the next decades<br> due to current pressure on water resources and the consequences of climate change, requiring highly<br> trained practitioners that can provide the knowledge and know-how on MAR implementation. The<br> present report is part of the Managed Aquifer Recharge Solution Training Network (MARSoluT ITN,<br> 2019-2023), which aimed to train experts in MAR.<br> The report deals with the objectives of work package four (WP4) of the MARSoluT project and aims at<br> helping to improve water quality by optimising MAR design at active MAR sites in Spain. The report<br> tackles four knowledge gaps on MAR in relation to water quality: (i) the need for a review of current<br> regulations on MAR and how they use Maximum Allowable Concentrations (MACs) to prevent water<br> pollution during MAR; (ii) a discussion on the current challenges for MAR water quality; (iii) the lack of<br> a conceptual model that can help in the creation of regulation, rules, and guidelines on MAR; and (iv)<br> the need for testing the efficacy of MACs at the national level with a focus on Spain.<br> Although this report focuses on Spain, it does not restrict its development to this country and has a<br> relatively broad scope, providing solutions for MAR worldwide. The methodologies in the current<br> report are mostly based on literature review of scientific, technical and regulatory documents and the<br> exploitation of published and unpublished water quality analyses and water quality standards involving<br> MAR.<br> For the first knowledge gap, a comprehensive review of existing regulations and guidelines for MAR<br> was conducted, and an analysis of MACs in water quality standards from diverse sources globally was<br> completed. To respond to the second knowledge gap, a discussion on modern water quality challenges<br> for MAR is provided, including the context, history, future and the need for a risk-based approach.<br> The Monitored and Intentional Recharge (MIR) conceptual model is a response to knowledge gap<br> three, comprising a set of nine blocks that elaborates on the most critical aspects that must be considered to draft MAR regulations and guidelines. This section also entails a series of recommendations<br> directed to future regulations on MAR, including developing a common terminology with legal implications, considering a permitting process, new legal development, the inclusion of budgetary aspects,<br> regard to the technical background for authorisation, and the fact that water standards for MAR must<br> be designed at the aquifer level.<br> The fourth knowledge gap was addressed through an analysis of source water quality in MAR sites in<br> Spain and a comparison between them and three European MAC-based standards (Italy, Spain, and<br> the Netherlands) to evaluate the efficacy of MAC in dealing with water pollution at MAR sites. This<br> section showed the high variability in terms of water quality at 11 MAR sites and the inadequacy of<br> MAC-based standards to control pollution while allowing for MAR implementation at the national or<br> European levels. This sort of standard could be useful aquifer-wide. This analysis also concluded that<br> focus on quality should be given to the final quality of the water after MAR rather than the original<br> water quality, and that the attenuation processes in the saturated and unsaturated zones should be<br> regarded. Finally, biochar, a promising low-cost material to remove multiple pollutants during MAR,<br> has been thoroughly studied.<br> This report also emphasises that, nowadays, MAR is an option, but in the future will likely become a<br> necessity, and that there is a need to continue investing in (1) applied research to improve insights into<br> the development of freshwater cones in saline environments, (2) define measures to increase the<br> efficiency of MAR systems and social acceptance, and (3), consider the beneficial impact of the<br> unsaturated and saturated zones.<br>