Demonstrating Managed Aquifer Recharge as a Solution to Water Scarcity and Drought

Final Report Summary - MARSOL (Demonstrating Managed Aquifer Recharge as a Solution to Water Scarcity and Drought)

Executive Summary:
The main objective of the MARSOL project was to demonstrate that Managed Aquifer Recharge (MAR) is a sound, safe and sustainable strategy that can be applied with great confidence. With this, MARSOL aimed to stimulate the use of reclaimed water and other alternative water sources in MAR and to optimize water resources management (WRM) through storage of excess water to be recovered in times of shortage or by influencing gradients. For this, MARSOL operated eight demonstration sites in six countries around the Mediterranean (Portugal, Spain, Italy, Greece, Malta, Israel) applying various technologies, i.e. infiltration ponds, river bed infiltration, direct injection wells, and river bank filtration, to infiltrate various water sources, i.e. river water, treated waste water, desalinated seawater, and surface runoff.
Operations at the demonstration sites were accompanied by supporting activities that collected, evaluated, and assessed data produced at the demonstration sites. These were organized in work packages on (i) innovative monitoring techniques, (ii) modelling, (iii) benchmarking, (iv) water quality issues, (v) economic feasibility considerations, (vi) risk and contingency plans, and (vii) legal issues and knowledge transfer for policy and governance.
The technical work packages could demonstrate that the MAR approaches in the various field sites using various water sources and infiltration and monitoring techniques are well understood, operate efficiently, and are also cost effective. The sites therefore are now serving as reference cases for MAR operations with proven technologies and sustained results. Selected sites operate with innovative product developments that have been finalized during the project, e.g. a highly efficient TDR system based on a modular concept and using freeware software solutions or decision support systems (DSS) based on wireless sensor network and open source data bases.

The major obstacles identified in the MARSOL project for an immediate and widespread implementation of MAR systems in the EU are therefore not related to technical aspects of the systems, but to water quality issues and the necessary regulatory framework. The overall number of contaminants identified in surface waters and especially in treated wastewater (84 organic micropollutants, including 52 human pharmaceuticals, 24 industrial chemicals, 5 food additives and 3 pesticides) are having a serious impact on the applicability of MAR for such water sources as well as on the public acceptance of MAR measures. Although it was demonstrated at several sites and in laboratory experiments that natural degradation processes are effective for some of the contaminants, other compounds are recalcitrant even under optimized infiltration schemes (e.g. diclofenac, carbamazepine). These findings collide with the water framework directive (WFD) that does not allow a deterioration of groundwater quality but asks for quality improvements. Therefore a regulatory framework is suggested that may serve as a reference for further exploitation. We see this as the sticking point for frequent implementation of MAR systems in the EU.

Overall, the MARSOL project produced innovative tools and technologies that can be applied at MAR sites and demonstrated their effectiveness under real world conditions at the demonstration sites. With this, the major requirements of the Inno-Demo call were clearly addressed. The project also identified obstacles that have to be tackled and provided first guidance how to address these issues in the future.

Project Context and Objectives:
1. Project context of MARSOL

The Mediterranean basin is one of the most sensitive regions of the world with respect to the likely climatic changes that are predicted as a result of human activities. According to the latest IPCC projections, average temperatures are expected to increase by 3.5°C by the end of the century and precipitation could decrease on average by more than 10%, with a larger decrease in summer and in the more southern areas. Despite the uncertainties in projections, the anticipated reduction of renewable water resources can be as high as 50% within the next 100 years, hitting regions that already suffer from water scarcity and droughts. In addition, the Mediterranean coastal zone represents already one of the most densely populated regions in the world with currently 180 million inhabitants, and 250 million expected by 2025 due to strong population growth. This will increase the demand for food, energy and other natural resources, putting additional stress on the diminishing water resources. As a further consequence, the deterioration of fresh groundwater resources due to intensive use of fertilizers in agriculture, pollution by industrial activities, or overexploitation of coastal aquifers resulting in seawater intrusion is already a reality.
At the same time, large water quantities are lost to the Mediterranean Sea as surface runoff and river discharge, discharge of treated and untreated wastewater, or as discharge of excess water from various sources during periods of low demand. These alternative water sources in principal can be used to increase water availability in general and in periods of high demand, and therefore improve water security. The main factors hindering the effective use of such waters are related to concerns about water quality, the lack of sufficient low cost intermediate storage options, and a lack of confidence in available concepts such as Managed Aquifer Recharge (MAR). However, storing water in aquifers during times of excess can help address water scarcity challenges experienced in many parts of the Mediterranean Basin. In principal, large storage capacity is available in shallow aquifers, either due to thick unsaturated zones or due to already depleted water resources in overexploited aquifers. In addition, water quality can be improved due to chemical and biological reactions during transport of the infiltrated water through the unsaturated and saturated zone, and by infiltrating waters for hydraulic control, e.g. to prevent seawater intrusion. Therefore, MAR, together with Soil-Aquifer-Treatment (SAT) systems and Aquifer Storage and Recovery (ASR) could be the key Water Resources Management (WRM) tool for tackling water scarcity in Southern Europe, the Mediterranean, and in water scarce regions worldwide by linking water reclamation, water reuse and water resources management.

The MARSOL project was designed to: (1) review, evaluate and expand the worldwide available scientific and experimental knowledge on MAR, (2) demonstrate the feasibility and efficiency of MAR in combating future water scarcity threats in the Circum-Mediterranean area using unique DEMO sites, and (3) develop innovative solutions that can be generally applied to arid and semi-arid regions. For this, the MARSOL consortium combines the expertise of consultancies, water suppliers, research institutions, and public authorities ensuring high practical relevance and market intimacy.
A total of eight field sites in six countries with a variety of running MAR facilities, MAR facilities that were ready for operation, and MAR facilities that have been designed and implemented during the MARSOL project ensured a coverage of the broad spectrum of potential water sources and MAR technical solutions that are available. The operators of all field sites offered a tailored information and training program on their respective sites for different stakeholders to demonstrate the potential of MAR for a variety of targets and under a variety of boundary conditions ensuring dissemination, public awareness and commercial exploitation.
MARSOL's demonstration sites are located in representative areas within the Mediterranean Basin to show that MAR can provide solutions for adaptive water resources management, i.e.:
• MAR as one of the most appropriate techniques to alleviate climate change adverse effects on water resources.
• MAR for sustaining drought mitigation and biodiversity goals.
• MAR to countermeasure temporal and spatial misfit of water availability.
• MAR to sustain agricultural water supply (considering aquifer overexploitation) and rural socio-economic development.
• MAR to combat agriculture related pollution as nitrates, pesticides, and even emerging pollutants.
• MAR to sustain future urban and industrial water supply as a key element for 'Smart Cities'.
• MAR to limit seawater intrusion in coastal aquifers.

With this, MARSOL tackled the very pressing problem of water scarcity in the Mediterranean, and in water scarce regions in general, by having a unique set of field sites for demonstration purposes and by having a broad scientific and engineering approach at these sites to cover the full application window for MAR technologies.

2. Main Objectives of MARSOL

Although MAR can be a key solution to Europe's and the worldwide water crisis, its application in the EU is rather limited to date. This is due to a mix of factors, including public perception, health risks, regulation, policy objections, availability of other water supply options, although they may be unsustainable (e.g. aquifer over-pumping) or energy intensive (desalination). Therefore, a multistep approach is followed, in which a sound technological basis is linked to a viable business case, and to an understanding of the social dimensions of MAR, including public acceptance and governance frameworks. Through this approach, a perception change might be achieved among economic sectors, policy makers, scientists and the general public, leading to a more open attitude with respect to MAR, advancing its consideration as a viable water option throughout the EU and influencing water resources management in other regions.
The overriding objective of MARSOL is therefore to demonstrate that MAR is a sound, safe and sustainable strategy that can be applied with great confidence. With this, MARSOL aims to stimulate the use of reclaimed water and other alternative water sources in MAR and to optimize WRM through storage of excess water to be recovered in times of shortage or by influencing gradients. Widespread application of MAR can help address water security problems to stimulate economic development, improve public health and well-being, and maintain ecological functions and biodiversity. The use of MAR technologies can substitute the need for other, more energy-intensive water supply options, such as the desalination of seawater.

MARSOL's main output is a powerful knowledge base of existing field applications of MAR technologies for addressing different societal challenges related to water availability. The effectiveness, efficiency and sustainability of existing MAR technologies is demonstrated, including operation, maintenance and monitoring procedures. Examples include different water sources, ranging from treated waste water to desalinated seawater and various technical solutions e.g. infiltration ponds, injection wells, river bed scarification, and hydraulic barriers against seawater intrusion. The pros and cons of each technology will be assessed systematically, and compared to alternative solutions. Economic costs and benefits of MAR options for the various economic sectors are quantified. Causes of public concern or acceptance of MAR are examined and proven ways to enhance public acceptability (e.g. through education and transfer of knowledge, evaluation of best practices) identified. Governance frameworks (laws, policies, institutions, etc.) that enhance the prospects of successful implementation of MAR are proposed. Finally, guidelines are developed for MAR site selection, technical realization, monitoring strategies, and modelling approaches to offer stakeholders a comprehensive, state of the art and proven toolbox for MAR implementation. The main objectives of MARSOL can therefore be summarized as:
• Demonstrate at 8 field sites that MAR is a sound, safe and sustainable strategy to increase the availability of freshwater under conditions of water scarcity.
• Improve the state of the art of MAR applications to enable low cost high efficiency MAR solutions that will create market opportunities for European Industry and SMEs (MAR to market).
• Promote the advantages of MAR by tailored training and dissemination programs to enable and accelerate market penetration.
• Deliver a key technology to face the challenge of increasing water scarcity in southern Europe, the Mediterranean and other regions of the world.

The eight field sites (DEMO sites) are the backbone of the project and are geographically distributed around the Mediterranean. They have been selected for the demonstration of different MAR objectives and technologies, and are using different water sources. The different MAR objectives were (i) replenishing over-exploited aquifers (Lavrion/Greece, Arenales/Spain, Llobregat/Spain, Brenta/Italy, Serchio/Italy), (ii) combating seawater intrusion (Lavrion/Greece, Malta South) (iii) improving the ecological and chemical status of aquifers (Algarve/Portugal, Llobregat/Spain, Brenta/Italy), (iv) Soil-Aquifer Treatment (SAT) (Lavrion/Greece, Arenales/Spain, Llobregat/Spain), and (v) seasonal storage and aquifer storage recovery of surplus fresh waters (Menashe/Israel). Different recharge technologies included (i) infiltration basins (Algarve/Portugal, Lavrion/Greece, Arenales/Spain, Llobregat/Spain, Menashe/Israel), (ii) ditches in a forested infiltration area (Brenta/Italy), (iii) river bank filtration (Serchio/Italy), infiltration wells for direct infiltration into the aquifer (Algarve/Portugal, Malta South), or others approaches, i.e. artificial wetlands, ditches, drainage pipes (Arenales/Spain). The different recharge water sources were (i) surface waters (Algarve/Portugal, Arenales/Spain, Llobregat/Spain, Brenta/Italy, Serchio/Italy), (ii) treated effluents (Lavrion/Greece, Algarve/Portugal, Arenales/Spain, Malta South), and (iii) desalinated seawater (Menashe/Israel).

By these various approaches, MARSOL will improve the integrated and sustainable management of water resources and ecosystems; it will also advance the potential of water reuse, due to water quality improvement during aquifer transport and storage, and it will demonstrate that salinization of coastal aquifers, an EU-wide phenomenon, can be counteracted through MAR. The large variety of demonstration sites with different water management problems and MAR objectives and approaches can demonstrate the viability of this technique for many different water resources situations not only in Europe but also in other regions in the world affected by water scarcity and drought.
The direct beneficiary of MAR solutions is the whole water sector, which can rely on improved water availability. These include farmers, water suppliers, industry, society and combined partnerships. The job creation potential and competitive advantage for EU industry will rise (i) from the development of a new market, for industry and SMEs, on MAR technical solutions capable of delivering the appropriate response to the increasing water needs, and also (ii) from the competitive opportunity created for the water users from the increase and reliability of water source, in terms of quantity and quality.

Project Results:
1. Overview

The project activities are structured in three Activity Lines (Fig. 1): Activity Line 1 "Horizontal Activities" consists of two work packages dealing with the Project Management (WP 1) and with Dissemination, Exploitation and Training Activities (WP 2). The technical work performed at the eight DEMO sites in six countries is conducted within Activity Line 2 "Demonstration Sites" (WP 3 to WP 10). Activities that support the demonstration activities and/or collect, evaluate, and assess data produced at the DEMO sites are grouped in Activity Line 3 "Integration and Impact". These activities include innovative monitoring techniques (WP 11), modelling (WP 12), technical solutions and benchmarking (WP 13), water quality issues (WP 14), economic feasibility considerations (WP 15), risk and contingency plans (WP 16), and legal issues and knowledge transfer for policy and governance (WP 17). Some of these could be considered as research activities; however they are deeply linked to the demonstration activities, by showing the impacts and the opportunities provided by each DEMO study, and simultaneously allowing comparison between study sites and results. A special focus is also on the knowledge transfer and dissemination of the results of the DEMO sites.
The following description of the main project results is organized according to the main structure of the project, summarizing activities on the sites as well as the results of the accompanying work packages that exploit the data generated at the sites. In depth presentations of the results of the different work-packages can be found in the respective deliverables.

2. Results of the MARSOL "Demonstration Sites" work packages

MARSOL operated eight demonstration sites in six countries (Portugal, Spain, Italy, Malta, Greece, and Israel) from which six out of the eight demonstration sites were either newly developed or upgraded during the MARSOL project. The overhauling of the existing sites and the construction of the new sites were accompanied by an extensive investigation and monitoring program using Geoprobe campaigns, geophysical methods, or tracer techniques. For this typically the project partners provided equipment and staff, or subcontracting was used. With this, an extensive basic data base related to the geological, hydrogeological, hydrochemical, and hydraulic conditions of the sites was established for further use.
All field sites were fully operational throughout the second half of the project and operated according to their specific objectives. This ensured a relevant time scale during which high quality data were generated at the sites as necessary input for the horizontal work packages. In the following the major activities and results achieved on the sites are summarized.

2.1 Lavrion, Greece (WP3)

The Lavrion site was newly developed during the MARSOL project with respect to MAR activities. Lavrion is located in the southeast coastal zone of Attica (Greece), within the area of Lavreotiki. The demonstration site is embedded in the Lavrion catchment that was selected as a potential target for MAR systems, as it is heavily used for agricultural purposes and exhibits already severe saltwater intrusion problems. The subsurface of the alluvial plain of the catchment as well as potential locations for the planned infiltration ponds were characterized by Geoprobe drilling activities (Fig. 2) as well as by geophysical methods. The Geoprobe direct-push vibro-coring activities included (i) EC loggings, (ii) aquifer hydraulic tests, and (iii) the installation of monitoring piezometers. A total of 20 monitoring piezometers were installed (with multi-level piezometer clusters at selected locations) at the coastal aquifer of Lavrion that are used for the continuous monitoring of the alluvial aquifer.
For the catchment the generated data allowed to develop a conceptual hydrologic model for the coastal hydro-system of Lavrion including the alluvial aquifer and the karstic aquifer system. The model was calibrated using water level time series of several monitoring wells in the alluvial plain aquifer as well as in the karstified aquifer. The model was then used to evaluate hypothetical scenarios for a full scale MAR implementation for the alluvial basin of Lavrion, to analyse the response of the aquifer system to different operation modes (i.e. to combat seawater intrusion, to satisfy irrigation needs of the study area of Lavrion, etc.) and to suggest the most favourable locations for the different purposes. To cover e.g. irrigation demand, it could be shown that, assuming a constant demand for the infiltrated water, about one million m³ of water could be infiltrated in six proposed infiltration ponds in the alluvial aquifer. This amount is in the range of the available water from the Lavrion waste water treatment plant. The Lavrion catchment and the developed model of the alluvial aquifer and the surrounding karstic region will be further used to test different modelling approaches, as it represents a typical setting for the Mediterranean.
The investigation data generated at the Lavrion Technological and Cultural Park allowed the selection of an appropriate site for construction of the experimental infiltration basins that were used to infiltrate waters of impaired quality, hence acting as a Soil-Aquifer-Treatment (SAT) system. Since implementation of the infiltration basins in year two of the project the site served as a reference site for the development and optimization of instrumentation for continuous monitoring of the infiltrating water through all hydrologic zones (surface, unsaturated and saturated zone). The developed TDR system for water content monitoring in the unsaturated zone proved to generate high quality data in high spatial and temporal resolution. The system is also competitive in terms of costs and is significantly more compact compared to available commercial solutions. In addition, a wireless sensor network connected to a real-time web-based platform was implemented that proved to be essential for the optimal operation of the SAT facilities.

One additional benefit of the Lavrion catchment and the Lavrion Technological and Cultural Park with the experimental infiltration basins is its use as a demonstration and training site for young scientists (undergraduate and postgraduate students) and for the public (Fig. 3).
These training activities are implemented in the study regulations for an international Master’s program at TU Darmstadt in Germany (TropHEE), and are as well part of the Bachelor's and Master's programs of the National Technical University of Athens (undergraduate students from the School of Mining & Metallurgical Engineering, postgraduate students from the MEng Programme ‘Water Resources Science & Technology’). With this, the site and the catchment serve for demonstration and dissemination activities well beyond the projects run-time.

Main results achieved at the Lavrion demonstration site include (i) a thorough characterisation of the subsurface in the Lavrion catchment and at the proposed site of the infiltration basins, (ii) a calibrated model of the Lavrion catchment for scenario analysis, and (iii) implemented experimental infiltration basins that were used for technology testing and optimization; in addition (iv) the field site is open as a training site for young scientists and the public.

2.2 Algarve, Portugal (WP4)

Field Activities in Algarve and Alentejo in Portugal were concentrated on three different aquifer systems, (i) the Rio Seco and Campina de Faro aquifer system in Algarve, (ii) the Querença-Silves limestone karstic aquifer system in Algarve, and (iii) the Melides aquifer, river and lagoon in Alentejo. The main objective of the field sites was to demonstrate how MAR can be efficient in solving specific groundwater quality problems in the Algarve and Alentejo regions that were caused by overexploitation of the aquifers, improper agricultural practices, and wastewater discharge.

In the Rio Seco and Campina de Faro aquifer system (Algarve) the main goal was to improve the quality of the groundwater that is heavily contaminated with nitrates, mainly due to inadequate agriculture practices. For this purpose, surface water surplus generated during strong rain events was being used in several infiltration basins that partly already existed in the Rio Seco river bed or have been constructed during the MARSOL project using heavy machinery (Fig. 4). Main purpose of the infiltration basins is to push the nitrate plume towards the sea. The efficiencies of the prepared river beds were analysed using salt tracer infiltration tests, and using monitoring data resulting from several natural runoff events in the project time. It could be shown, that an immediate response of the water tables below the prepared river beds occurred, indicating the high infiltration rates. Furthermore, the potential of existing large-diameter wells has been explored to be used as a potential MAR facility to infiltrate runoff water from greenhouses.

In the Querença-Silves limestone karstic aquifer system (Algarve) two main demonstration activities with two main goals have been operated: 1) To improve the water quality of treated effluents from São Bartolomeu de Messines waste water treatment plant before the discharge of the water into the Ribeiro Meirinho river that recharges the karstic aquifer. For this two infiltration basins were constructed in the framework of the MARSOL Project. Specifically, the fate of pharmaceuticals were monitored in the infiltration basins, as in total 24 pharmaceuticals were analysed in the treated waste water from the São Bartolomeu de Messines waste water treatment plant. For all compounds, some decrease in concentration during infiltration occurred, i.e. for diclofenac, metoprolol, propranolol, sotalol, atenolol, ibuprofen and carbamazepine. Although no direct proof of degradation was obtained, analyses of the sediment in the basins showed no detection of pharmaceuticals, indicating that biodegradation may have occurred. 2) To increase groundwater storage at Cerro do Bardo karstic area using wet years surface water surplus stored in Águas do Algarve water supply Odelouca and Funcho reservoirs to increase the water availability in dry years and facilitate downstream water supply. This was achieved through infiltration into a rehabilitated large diameter well, for which a pipeline of more than 1300 m length was constructed to supply water to the well (Fig.5). In several infiltration tests it was shown that in principal the well can be used for groundwater recharge, although infiltration rates decreased exponentially over time. Further testing is needed before regular operation of such wells.

For the Melides aquifer, river and lagoon (Alentejo) the main goal of the MARSOL project was to evaluate the options to remove rice field contaminants, nitrate and pesticides, prior to their discharge in the Melides lagoon through soil-aquifer-treatment (SAT-MAR). A set of column experiments was performed to determine hydraulic conductivities of the native soil, and it was found to be well suited for a MAR facility. A container experiment ('sandbox model') was constructed and filled with soil from a potential infiltration site to (i) analyse infiltration capacities, and (ii) to determine the fate of contaminants during infiltration. With this, the necessary data base is generated for a field implementation of an infiltration scheme.

Main results achieved at the Algarve and Alentejo sites in Portugal were (i) the implementation of infiltration sites in the river bed of the Rio Seco and the demonstration of their efficiency in infiltrating stormwater runoff, (iii) the establishment of infiltration basins to treat effluents from São Bartolomeu de Messines waste water treatment and (iii) to show that pharmaceuticals can be effectively attenuated during infiltration, and (iv) the construction of physical sandbox models to investigate the infiltration behaviour of waters and the fate of contaminants therein.

2.3 Arenales, Spain (WP5)

The Los Arenales Aquifer in Castille de Leon has a history of over-exploitation since the seventies, due to agricultural activities in the region. MAR activities started in 2002, and today MAR facilities are concentrated in the Santiuste basin, the El Caracillo District, and in the Alcarazèn region. For the MARSOL project, specifically the Santiuste Basin with five infiltration ponds, one artificial wetland, three open infiltration wells, and river bank filtration for municipality supply were analysed, as well as the Carracillo Basin with three infiltration ponds, one artificial wetland and one infiltration field (flood and controlled spreading). Also river bank filtration for irrigation is implemented. Fig. 6 shows some typical components of the MAR installations.
In the frame of the already existing MAR infrastructure in the area, the MARSOL project aimed to (i) refurbish several components, (ii) install additional monitoring equipment and monitoring piezometers, and (iii) generate data on water quality in several sampling campaigns. In the Caracillo basin, e.g. eight new piezometers were constructed around an infiltration pond to analyse infiltrating water fronts in detail.

Due to the vast existing MAR infrastructure in the Arenales region, the various applied designs, and the comparably long time since implementation resulting in a good data base, the Arenales demonstration sites were used to study some of the crucial topics for the long-term operation of MAR facilities in detail. Specifically, clogging phenomena have been investigated. Water quality parameters along MAR canals have been related to various clogging processes. Five clogging typologies could be identified and it was found that there is a direct relation for several quality parameters with the different types of clogging, with a direct correlation to parameters such as nitrates, sulphates, and the sodium and potassium distribution.
With relation to gas clogging, the main activities have been (i) the construction of a new monitoring station to study unsaturated zone processes, and (ii) the installation of new soil moisture and temperature sensors in two previous existing stations. The rational for this was the observation that gas clogging is one of the most important factors related to the reduction of infiltration rates at the Los Arenales installations. The new installations allowed the collection of data series for three recharge cycles. It was observed that turbulent water flow and cascading water resulted in an increased clogging. Anti-cascading lock-gates installed in the infiltration canals proved to be an effective measure to prevent such clogging effects.
In addition, the determination of treated wastewater quality improvements during water flow along conduits and canals was studied. The system consisted of (i) a canal without obvious plant growth for initial transmission of the water, (ii) a section of the canal with dense plant growth ('green biofilter'), and finally (iii) a constructed wetland for infiltration ('Triplet', Fig. 7).
Water quality improvements for basic parameters could be shown along the water flow, especially for nitrate, some heavy metals, and turbidity.
The experiences over the last years and during the MARSOL project for the operation of the MAR facilities in the Arenales area allow some general conclusions to be drawn. The impact on the rural development have been significant, the demonstration sites stand for diverse and successful examples of MAR implementation. There are remarkable advantages of such installations, e.g. the aquifer as an underground water supplier to every well, or cost effectiveness, as reduced pumping needs by the increased groundwater level. Cost analyses showed that the overall operation and maintenance costs are low (0.05 - 0.1 €/m³).
Another lesson learned in Arenales is that the participation of stakeholders, specifically farmers and the responsible actors in water management has a direct and positive impact on the public acceptance of MAR. In a region like Arenales, where agriculture is one of the most important economic factors, the positive effects of MAR are visible to a large fraction of the public. The demonstration sites are part of the landscape and the public acceptance enables the implementation of new MAR facilities without major problems. The Arenales region might serve as a blueprint for a successful implementation of MAR in a general water management strategy.

Main results achieved at the Arenales demonstration sites in Spain were (i) the refurbishment of existing infrastructure and installation of additional monitoring equipment, (ii) the determination of clogging causes and the development of counter-measures, (iii) engineered water distribution structures may improve water quality prior to infiltration, and (iv) operation and maintenance costs after about 15 years of operation are between 0.05 and 0.1 €/m³, indicating the high competitiveness of the installations.

2.4 Llobregat, Spain (WP6)

At the Llobregat River demonstration site, MAR is applied in surface infiltration ponds. The site operates in a two-step approach, consisting of a sedimentation pond and an infiltration pond. Water to feed the ponds is diverted from the local Llobregat River. Recovery is not done at the same site, but through a number of extraction wells that are located down-gradient. The overall objective at the site is to demonstrate the potential of MAR to increase groundwater quantity and improve groundwater quality in the Llobregat aquifer to support water supply for the Barcelona metropolitan area.

The site was implemented before the start of the MARSOL project and has been extensively monitored during several periods over time in terms of infiltration rates and also on geochemical variations of the infiltrated water. Most important for the site, a vegetal compost-made reactive organic layer was placed at the bottom of the infiltration pond (Fig. 8). The objective of the reactive layer was to provide a large amount of labile organic carbon that can be dissolved in the infiltrating water in order to promote biogeochemical reactions, i.e. degradation of organic contaminants including emerging compounds such as personal care products or pharmaceuticals. During the first months after the organic layer was installed, an improvement in the elimination of some pollutants present in the recharge water was observed, leading to a positive impact on the quality of the recharged water. The impact of the organic layer on longer time scales and an in-depth analysis of the biogeochemical processes had not been done before the start of MARSOL.
Activities on the site included the analysis of clogging effects due to microbial growth that limits infiltration rates but at the same time might promote biogeochemical reactions. In order to assess the effect of biofilm formation on the loss of infiltration capacity of the pond, two field campaigns were performed in July 2014 and March 2015. The first one refers to wetting period and the second one, to dry conditions (under natural conditions). Soil samples were taken distributed along the sedimentation pond, from the reactive layer, the vadose zone and groundwater and analysed for 16S rDNA. Microbial population richness and equitability were measured from DGGE band profiles by the Shannon Index (H) and Pielou's Evenness Index (E). The results showed that the microbial population is highly dependent on water content (drying versus flooding) and fully controlled by the presence of the reactive layer at the bottom of the pond. In general, microbial communities found showed a large microbial diversity, capable to promote a variety of biogeochemical reactions.
Laboratory column and batch experiments accompanied the field investigations and focused on contaminant fate, especially with respect to nitrate and pharmaceuticals. In both cases the promoting effect of the organic rich compost layer could be shown. In the case of nitrate, the reactive layer induces reducing conditions and with this effective nitrate reduction. This could be shown for fresh compost as well as for aged compost recovered after three years from the reactive layer in the infiltration pond (Fig. 9, left). Denitrification could also be proved to occur in the field by stable nitrogen isotope fractionation patterns, and even under drying conditions, e.g. with the potential presence of oxygen under unsaturated conditions, denitrification was occurring in some parts of the reactive layer. These findings highlight the long-term positive effect of the reactive layer with respect to nitrate reduction.
From the group of pharmaceuticals, degradation behaviour of sulfamethoxazole (SMX) was studied in detail. For this, nitrate reducing conditions were established in batch experiments with soil and synthetic groundwater by adding sodium acetate and methanol. SMX was degraded in the experiments under denitrifying conditions with two metabolites forming (4-nitro-SMX and desamino-SMX), however these metabolites are not stable and are retransformed to the parent compound, directly in the case of 4-nitro-SMX or with a previous transformation to a nitro compound for desamino-SMX. The molecular mechanism proposed for the re-transformation is reductive degradation, similar to the degradation of nitrobenzene to aniline, involving an overall inclusion of 6H+ and the removal of 2H2O molecules. The reductive degradation could be mediated biotically or abiotically, with no information available to allow discriminating between them. The proposed pathway is given in Fig. 9.

Main results achieved at the Llobregat demonstration site in Spain were (i) the identification of highly diverse microbial communities in the soil beneath the infiltration pond, (ii) the prove of the beneficial effects of a reactive humus layer at the bottom of the pond for nitrate reduction, (iii) the long term stability of the denitrification processes, and (iv) the identification of sulfamethoxazole degradation pathways.

2.5 Brenta, Italy (WP7)

In the River Brenta Catchment, Vicenza, Italy, two demonstration sites are located, (i) the Schiavon Forested Infiltration Area (FIA) having an area of 16,200 m² and being fed by the Brenta river through irrigation canals, and (ii) the Loria retention basin, a flood storage and infiltration basin with a size of about 20,350 m² and a volume of 30,000 m³, next to the river Lugana (Fig. 10). Both sites have been in operation before MARSOL, and the Schiavon FIA has been part of the LIFE+ project Aquor.

During the MARSOL project, both sites were characterized in depth to get a detailed knowledge of subsurface structures that is vital to understand infiltration processes. For this the MOSAIC (MOdel driven Site Assessment Information and Control) approach was employed by MARSOL partner UFZ for a problem-oriented and rapid site characterization. The MOSAIC platform comprises mobile modular data acquisition units for adaptive field investigations and contains vehicles equipped with direct push probing devices in combination with geophysical measuring techniques as well as hydrogeological and geotechnical equipment. Thereby, surface geophysics allow rapid mapping of subsurface structures while direct push technologies can be used for high resolution in situ parametrization of detected layers/units.
At the Schiavon forested infiltration site and at the Loria infiltration basin, investigations included (i) extensive electromagnetic profiling and gamma-ray spectrometric measurements to characterize the heterogeneity of the subsurface; (ii) hood infiltrometer tests to determine infiltration rates and spatial variability of infiltration rates; (iii) soil sampling for grain size analyses and to conduct laboratory soil column experiments to analyse changes of infiltration capacity in response to potential colmation; and (iv) cone penetration testing (CPT) in combination with frequency domain reflectometry for water content profiling. Natural clay layers were reliably detected at the Loria site using direct push profiling. Direct push electrical conductivity allowed then an exact determination of layer depth and thickness. On both sites heterogeneous subsurface structures were encountered demonstrating that the selection of locations for infiltration infrastructure needs to be carefully done based on (hydro-)geological as well as hydrological aspects (e.g. sediment loads), to allow an efficient and economically sound system operation. It was demonstrated that a reliable, flexible, and economic site characterization approach is a key for this.
In addition, on both sites prototype TDR sensors developed by the partner ICCS were installed. The optimal locations for the TDR sensors were selected based on the information from the site investigation program. The systems consist of low loss coaxial cables for the TDR signal that were sealed and connected to the TDR monitoring and data-logging system. This allowed monitoring of soil water content in high spatial and temporal resolution into a depth of about 4 m below ground surface (Fig. 11).
Further activities on the sites included an extensive water quality and quantity monitoring program. The main physical-chemical parameters and the volume of infiltrated water are measured. Monthly laboratory analysis of surface water were performed for the following parameters: specific electric conductivity, turbidity, pH, total hardness, chlorides, nitrates, sulphates, ammonia, nitrites, arsenic, cadmium, total chromium, nickel, lead, copper, Escherichia coli, enterococci, total coliform. Monthly laboratory analysis of groundwater included the same parameters plus trichloroethane, trichloroethylene, tetrachloroethylene. Also, water table levels were measured monthly.
Finally, a 3D physically-based distributed hydrological model of surface/subsurface water for the Brenta basin was developed as a tool to simulate the whole hydrological cycle and perform spatial-temporal analysis for water management and planning, using open source and free codes. In addition, such a model, once calibrated on the basis of recorded historical data, can also be employed for evaluating the effects on the aquifers of some MAR techniques, such as those ones that were established inside the Brenta basin.

On the basis of the results obtained by the modelling activities carried out, it is possible to ascertain that similar MAR strategies could be considered valuable options to replenish the unconfined aquifer of the Brenta megafan, recently affected by a significant and generalized drop in groundwater heads due to heavy exploitation, massive land-use change and climate change. It was demonstrated that, if MAR technologies were extended over an area of about 100 ha, the resulting potential annual recharge would be about 30 million m³, i.e. near to the total capacity of the Corlo reservoir that represents presently one of the main water resources in this area.

Main results achieved at the Brenta demonstration sites in Italy were (i) the in-depth characterization of the subsurface of the infiltration basins using geophysical and direct push technologies, (ii) implementation of a novel TDR system for monitoring of water content in the subsurface in high spatial and temporal resolution, (iii) implementation of a partly online monitoring program to analyse surface water and groundwater, and (iv) the development of a 3D distributed hydrological model for scenario analyses.

2.6 Serchio, Italy (WP8)

The Induced River Bank Filtration (IRBF) scheme along the Serchio River in Sant'Alessio near Lucca (Tuscany, Italy) allows the abstraction of an overall amount of about 0.5 m³/s of groundwater providing drinking water for about 300,000 people of the coastal Tuscany area (town of Lucca, Pisa and Livorno). Water is pumped by ten vertical wells (four of the Sant'Alessio pumping station and six to the Pisa-Livorno main pipeline) inducing river bank filtration into a high yield (10-2 m²/s transmissivity) sand and gravel aquifer. A down-stream weir raises the river head and increases water storage in the aquifer along the river reach (Fig. 12, left). Surface geology is characterised by unconsolidated silty to sandy sediments, while in the Serchio riverbed coarse clean gravels outcrop as well as sand bars. Knowledge developed prior to the FP7 MARSOL project (mainly developed within the LIFE project SERIAL-WELFIR) led to the setup of a steady state groundwater flow model of the Sant'Alessio plain.

To understand the well field hydrology and flow regime at the site several extensive Geoprobe campaigns have been conducted from 2014 to 2016 (Fig. 12, right). In the first campaign, the focus was on a detailed characterization of the subsurface hydro-stratigraphy. Direct push electrical conductivity profiling as well as direct push injection logging in combination with direct push pneumatic slug testing was employed.
A total of 410 relative hydraulic conductivity measurements were performed for high resolution vertical hydraulic subsurface characterization. Also, a total of 15 ground water monitoring wells (total installation length 200 m) as a basis for detailed monitoring of ground water dynamics at the well field site have been installed.
In two additional campaigns tracer tests were performed after in depth characterization of a selected site within the well field. First, two heat tracer experiments were conducted in the gravel deposits of the Serchio river flood plain during two field campaigns in 2015 and 2016. Despite rapid adaptation of the tracer test field layout, no tracer signal was captured in the observation wells. A complete or partial miss of the tracer is not uncommon in hydrogeological field practice and can happen for several reasons. In this case, results from an exploratory 2D groundwater flow and solute transport model indicated a non-sufficient amount of hot water injection during the first test in 2015 with respect to the monitoring well field layout. To overcome existing lack in field methods, a novel tracer test was designed combining a conventional salt tracer with heat. This novel tracer test concepts allows reliable determination of the groundwater flow direction and velocity with on-site decision-making to adaptively install observation wells for reliable breakthrough curve measurements. Furthermore, direct-push vertical electrical profiling provided essential information about the plume characteristics with outstanding measurement resolution and efficiency. Two consecutive tracer tests were performed in 2016. The temperature and electrical conductivity monitoring data of the observation wells showed a clear retardation of the heat tracer in comparison with the salt tracer. In addition, a flow and transport model was setup up using MT3D in combination with SEAWAT (SEAWAT to consider density effects caused by the high concentration of the salt tracer and hot water injection) to jointly analyse the heat and salt tracer break-through-curve and direct push logging information. Based on the results a ground water flow velocity of up to 26 m/d was estimated, significantly higher than predicted by an exploratory 2D groundwater flow and solute transport model.
Based on the results of the subsurface investigations and tracer tests an adapted monitoring strategy of the site was developed. Two different monitoring schemes were designed including both surface and groundwater monitoring points. A first network including almost the whole Sant'Alessio plain (Large Area Monitoring Network - LAMN) where discrete sampling for water quality and piezometric head was performed typically on monthly basis, and a second experimental area around Well 5 (Experimental Area Monitoring Network - EXAMN) of the Sant'Alessio well field, where in addition to the monthly monitoring, a continuous monitoring system was installed with six piezometer clusters.
The continuous recording components of the monitoring system were connected through a Wireless Sensor Network (WSN), including measurement points in surface and groundwater. Such a network is an integrated system comprising three different sources of information: (i) five sensors endowed with a customized acquisition technology based on open source hardware and software, specifically developed for the project; (ii) a multi-parameter probe to monitor several quality parameters in groundwater; and (iiI) an additional connection with the real-time monitoring point managed by the Regional Hydrological Service (Tuscany, Italy), active on the Serchio river. The integration of these different sources is realized through a geographical database (GeoDB) into which all data measured and acquired are fed online.

All data gathered at the site were used to implement a Decision Support System (DSS) that allows the operators of the site to monitor water quantity and quality on-line and to analyse different future scenarios for their decision making. Therefore, the DSS is aimed at both, controlling and analysing measured parameters and managing and suggesting new scenarios for the well field. The paradigm for the DSS development was the application of only free and open source software tools, which contributes to ensure an easy replicability of the selected architecture at different MAR sites, as well as a cost-saving and high customizable application.
The DSS architecture is based on two components: 1) On the server side a geographical database (GeoDB). The GeoDB has been developed using PostgreSQL (2014) as relational database manager system (with PostGIS as spatial extension), and hosted on a virtual machine in TEA SISTEMI’s server farm, using Linux OS with Debian 7.2 (wheezy) distribution. 2) On the client side a QGIS as GIS desktop platform. Hydrological/hydrogeological numerical models can be set up and run in QGIS using the FREEWAT plugin, developed in the ongoing homonymous H2020 project (www.freewat.eu).

Main results achieved at the Sant'Alessio well field in Italy were (i) an in-depth investigation of the well field hydrology and flow regime using Geoprobe direct push technologies and tracer tests, (ii) the implementation of a tailored monitoring network and strategy for the site, (iii) the development of a wireless sensor network connected to a geographical database (GeoDB) for real time data collection and visualization, and (iv) a decision support system (DSS) to monitor water quantity and quality on-line and to analyse different future scenarios for decision making.

2.7 Menashe, Israel (WP9)

During the last decade, five desalination plants were built along the coast in Israel, already leading in times of low demand to an excess of desalinated water. Storage in the coastal aquifer by artificial recharge may be a possible solution for such surpluses. The Menashe MAR site that was selected to accommodate such surpluses is located on sand dunes overlaying the northern part of the Israeli Coastal Aquifer, close to the city of Hadera. Operating since 1967 it diverts natural ephemeral surface flow into a settling pond and from there to three infiltration ponds (Fig. 14). In the vast majority of runoff events only the two northern infiltration ponds are used. Therefore, the southern infiltration pond is now dedicated to the infiltration of surpluses of desalinated seawater from the nearby Hadera desalination plant, located about 4 km to the west.

The site was designed to enable both, the monitoring of operational MAR events in which 50,000 to a few millions m³ of desalinated water are discharged into the infiltration basin, according to water supply considerations of Mekorot and the Water Authority, and to allow well designed, controlled and monitored infiltration experiments with small volumes of desalinated water (some 100 m³) to be performed in the framework of MARSOL.
For vadose zone monitoring, a gallery including five silicon-carbide suction cups (at 50, 100, 200, 300, and 460 cm below surface) and seven soil sensors (at 50, 100, 150, 200, 250, 300 and 400 cm below surface) monitoring volumetric water content (WC), bulk electrical conductivity (EC) and temperature (T) were installed. Another silicon-carbide suction cup was installed at 500 cm below surface in a distance of about 100 m away from the gallery. In addition, soil samples were taken close to the surface and from depths of down to 30 m during drilling of groundwater monitoring wells for further characterization (i.e. grain size distribution, carbonate content) and to be used in further laboratory experiments.
Over the course of the project, several large-scale and experimental-scale infiltration events were monitored through the installed sensors. The system was able to capture the infiltrating water fronts as well as the changes in temperature and electrical conductivities very well. Infiltration rates were as high as 50 cm/hour for the dry unsaturated zone and decreased to values of about 1 cm/hour for fully saturated conditions, due to the presence of clayey zones limiting infiltration.
Field experiments were accompanied by laboratory column experiments with two main focal points, (i) to investigate the evolution of major ions in the water, since the desalinated water is low in ions and is infiltrated into a carbonate-containing sediment, and (ii) to assess the potential formation of disinfection by-products (DBP) as the desalinated water is already chlorinated when it is discharged into the infiltration pond.
The saturated column experiments designed to reflect hydrochemical changes revealed that at the time scales of 30 pore volumes ion exchange is the major reaction in the sediment, besides mixing. The more CaCO3 in the sediment the longer the exchange reactions will last. The driving force for exchange is the different Ca/cation ratio between desalinated water and natural groundwater. For example Ca/Mg in desalinated water is 8.4 times larger in desalinated water than in the groundwater (the highest from all Ca/cation ratios). Hence when desalinated water flows into a sediment saturated with groundwater Ca adsorbs and Mg desorbs rising the Mg concentration up to 6 mg/L larger than expected for pure mixing. The aquifer materials – especially the sediments containing significant mass of lime – therefore act as ion exchangers to some extent. A positive result of occasional MAR events with desalinated water to the aquifer is that the lack of Mg2+ in the desalinated water is thus partly compensated by the sediments. This compensation will not last forever but will stay for some time. At periods when natural groundwater will flow again in that part of the sediment it will be regenerated with Mg2+ ready for compensation in the next MAR event.

Results of the study of the formation of disinfection by-products (DBP) due to infiltration of chlorinated desalinated seawater through the soil column in laboratory and field experiments showed that trihalomethanes (THM) form in the subsurface, regardless of the low organic content in the sandy sediments. Nevertheless, their concentrations are at least one order of magnitude lower than the maximum allowed concentrations both by EPA and WHO. All four forms, CHCl3, CHCl2Br, CHClBr2 and CHBr3 were detected in the top 3 meters of the vadose zone pore water at single microgram/L levels. In shallow groundwater (around 20 m below surface) THMs concentrations were below the detection limit. Both laboratory and field results showed higher concentrations of total THM after 3 hrs of contact between the desalinated water and the infiltration pond soil than after 1 hour, yet longer than few hours of incubation does not increase further the formation of THM. In general the THM concentrations were found to strongly dependent on bromide concentrations which are estimated to be around 30 μg/L in the desalinated water. Additionally, their concentration is also dictated by the low organic content which was found to be only up to 0.2% in sandy top-soil samples. Thus, the formation potential of THM in the site is low, and was also estimated in laboratory experiments to span at the single μg/L range.
For both, the processes in the unsaturated zone and for the wider area of the infiltration pond, numerical models were set up. For the unsaturated zone this was done using Hydros-1D. Using information on the subsurface stratigraphy the model was well able to capture the infiltration behaviour during recharge.

A conservative regional transport model was set up covering about 65 km², using the MT3DMS software (Fig. 15, left). MT3DMS is a modular three-dimensional transport model which operates in conjunction with MODFLOW in a two-step flow and transport simulation. Considering advection and dispersion processes, the transport model simulated the spatial distribution of the recharged desalinated water body over time. As an example, for the January 2015 and January 2016 infiltration events Fig. 15 (right) shows the fraction of desalinated water in the groundwater for June 2016.

Main results achieved at the Menashe infiltration site in Israel were (i) the implementation of a monitoring system to study infiltration behaviour, with infiltration rates being between 50 cm/hour and 1 cm/hour, (ii) the quality of the infiltrated desalinated seawater is improved with respect to magnesium, due to ion exchange, (iii) the formation of DBP was shown at the infiltration site, but concentrations are low compared to legal limits, and (iv) an operative calibrated flow and transport model accounting for the MAR operations from the surface to the regional aquifer was developed and is already used operationally as a decision support system in Mekorot.

2.8 Malta South, Malta (WP10)

Agricultural activities on the island of Malta with the extraction of groundwater for irrigation purposes caused a decline of groundwater levels resulting in seawater intrusion at the coastlines. The main scope of the activities in South Malta is therefore the implementation of an artificial recharge scheme which the utilisation of highly polished treated sewage effluents to raise regional piezometric groundwater levels and with this to create a seawater intrusion barrier. Moreover, the sustainable yield of the regional aquifer system can be increased, benefiting agriculture in the region. The treated effluents would have otherwise been discharged directly to the sea.

As the treated water is directly injected into the coastal aquifer a multi-barrier effluent polishing process has been developed by the Water Services Corporation (WSC). The aim is to achieve high quality levels in the final polished effluent produced in the wastewater treatment plant in Malta South. The effluent treatment/polishing processes include four treatment steps, namely (i) conventional wastewater treatment, (ii) ultra-filtration, (iii) reverse-osmosis, and (iv) advanced oxidation. For monitoring of the water quality after the conventional wastewater treatment and after the following three advanced steps, 65 target parameters, including, e.g. pharmaceuticals, artificial sweeteners, pesticides, and organic chemicals, were analysed. It was shown that in the conventionally treated effluent 30 compounds were still detected, while after the advanced steps only five compounds were detected in greatly reduced concentrations, including two plasticizers and two industrial chemicals.
For implementation of the injection gallery, a line of coastal boreholes were drilled (Fig. 16, marked in green) through which highly polished treated sewage effluent of better quality compared to the native groundwater is directly injected to the saturated zone. A series of monitoring boreholes were also drilled upstream of the plant (Fig. 16, marked in yellow).
In addition to the four monitoring wells at the wastewater treatment plant three regional groundwater monitoring stations have been established under the MARSOL project to monitor the impact of the Malta South Managed Aquifer Recharge pilot project. These monitoring wells were in operation prior to the actual start of the artificial recharge pilot action in order to enable the collation of sufficient data on the background status of the regional aquifer system. This information will permit the undertaking of comparative analysis on the status of the aquifer system before and after the initiation of the MAR pilot action. Furthermore, it is planned that the monitoring network be maintained even following the closure of the project to enable the assessment of the long term impacts of the MAR scheme.
For scenario analyses, a large scale 3D groundwater model of the southern part of Malta was developed and density-coupled flow and transport was simulated using the commercial code FEFLOW in order to analyse the effect of MAR in the seawater intrusion at Malta Island. After calibration, the model was run for the years of 1944 to 2016. The effect of the groundwater abstractions from public supply and agriculture on groundwater levels and the resulting mass concentration was evident when comparing the situation in 1999 and 2016 with the reference year of 1944. Of particular importance is the effect of the abstraction galleries, which appear to induce a significant drawdown on the groundwater level of the system. Considering the results obtained for 2016, new model simulations were prepared considering the injection of the surplus of wastewater (2 hm³/year) for 10 years (2016-2026) in the southeast area of the model, in the location proposed for the MAR gallery in order to assess the effect of this MAR activity in the aquifer.
The model shows that already after one year of assumed MAR operation a significant effect is visible for the southeast part of the model, resulting in a groundwater level rise and decrease in seawater intrusion. Although there is a positive impact from the injection, this is not felt far from the injection point, as can be seen from Fig. 17 on the right, showing it is evident that only the south-eastern sector is affected by the injected water. It is important to note that according to the model and the particle tracking applied, all of the injected water flows directly to the sea. Therefore, the injection of residual wastewater is not jeopardizing the public supply abstractions location upstream in the island.
As it is expected, the scenario of MAR will create a barrier of freshwater in the south-eastern sector of the aquifer when compared with the 'business as usual' scenario.

Main results achieved at the Malta South site in Malta were (i) the implementation of a monitoring system to study the effect of the infiltration of highly polished effluents into the coastal aquifer, (ii) the construction of infiltration wells and a distribution system for the effluent, (iii) the proof that the multi barrier treatment system produces high quality water with respect to micropollutants, and (iv) a calibrated large scale 3D groundwater model that is used for scenario analyses and that shows the beneficiary effect of the infiltration.

3. Results of the MARSOL “Integration and Impact” work packages

Activity Line 3 "Integration and Impact" was designed to support the demonstration activities and/or collect, evaluate, and assess data produced at the demonstration sites. The work packages in this Activity Line served several purposes, they were directed to (i) collect data from all sites allowing comparison between study sites and results, (ii) addressing issues that were of overriding importance for MAR as a technology, and (iii) were producing outputs that could be disseminated and would serve as reference for the general applicability of MAR, e.g. white books, best practise guidelines, or state-of-the-art technical analyses. Activity Line 3 is therefore considered to be of exceptional importance as deliverables are typically open to the public and may serve as references for stakeholders.

3.1 Investigation and Monitoring (WP11)

This work package was dealing with two main activities, the compilation and evaluation of investigation and monitoring strategies at MAR sites, and the further development of specific sensor and IT technologies related to the monitoring of operational MAR sites. For the first activity, a best practice guideline for the selection of appropriate investigation and monitoring strategies and systems for MAR facilities was elaborated.

Monitoring of MAR sites is crucial for performance evaluation and site management. Therefore, in this work package specific sensor systems, relying on established technologies, were optimized and tailored for the use in MAR. Besides other techniques, time domain reflectometry (TDR) is one of the key techniques to monitor water saturation in the unsaturated zone, and therefore a TDR system was constructed that provides real-time continuous measurements of the water saturation in the unsaturated zone below a SAT basin. In Lavrion a prototype is installed that is composed of an integrated system of low cost and energy efficient components such as: (i) processing mainboard, (ii) Micro-controller, (iii) D/C converter, (iv) RF Switch, and (v) TDR pulse generator (Fig. 18). With this, monitoring of soil water content is possible in high vertical resolution. The same system was also successfully installed and operated at the demonstration sites in Italy.
As a complementary monitoring technique, two different radar-based sensors to achieve two distinct objectives were developed that allowed to quantify the infiltration rate of percolating water through the unsaturated zone, and to detect and analyse the cavitational characteristics of an underlying karstic conduit network and provide information on the qualitative characteristics of the contained groundwater within depths of approximately 20-30 m below ground surface.
Collecting data in high spatial and temporal resolution and making them available in real time requires appropriate data transmission and storage technologies. A common and innovative approach is the use of self-organizing ad-hoc wireless sensor networks including appropriate data storage and visualization techniques (web based data management platform). The most important features are the wireless transmission of the data, which results in the possibility of an adaptive process oriented design including an open platform to connect sensors and actuators.
To demonstrate this state-of-the-art technology related to the MAR concept, a wireless sensor network on a modular hardware design, including web based data management platform, was developed and installed in Lavrion. A system board was designed containing a TI SitaraAM 3305/17 processor (ARMv7 architecture, ARM Cortex-A8 core) running at 600 MHz. This board also provides 256 MB of RAM, 512 MB of flash memory, an RJ45 Ethernet port, two USB ports, an SD card slot, and a RS-232 serial port. Being a versatile platform for a variety of application scenarios, it acts as the central hardware component of the network. Additionally, the processor board can be paired with an extension board offering additional and more specialized interfaces. The concept allows for arbitrary extension boards to be realized. The connecting to usual IT infrastructures can be accomplished either directly per LAN, using WiFi or via a mobile data connection (e.g. via UMTS USB modem). The processor board itself consumes not more than 1.7W under full load. Peripherals such as the various USB transceivers and additional USB Ethernet adapters may raise this to approximately 10 W. The mainly electronical components which are built inside a node are the Transceiver Module for the data exchange in the wireless network and the data acquisition circuit to convert and pre-process the sensor signal. The data acquisition module is designed for future sensor integrations and can handle the most occurring physical signals and digital interfaces (Fig. 19).

To collect the information gathered, a web-based MARSOL data platform was designed to provide long-term statistical series of specific hydrologic variables for the analysis of the MAR facilities which will be used to derive efficient prevention, mitigation and adaptation strategies. The portal application combines all data collected from the individual sensors and therefore it can serve as a database node to provide scientists and decision makers with reliable and well accessible data and data products. In particular, the collected data from the different demonstration sites in MARSOL are stored in a database carefully designed for the purposes of each site. In addition, a graphical user interface was designed offering interaction with the user and visualizing the results.

Main results achieved at in the Investigation and Monitoring work package were (i) an overview guideline of available investigation and monitoring techniques for MAR sites, (ii) a low cost optimized TDR system for monitoring of water content in the unsaturated zone in high spatial and temporal resolution, (iii) a wireless sensor network for real time data transmission and storage, and (iv) a web based platform as a user friendly interface for data analyses and decision making.

3.2 Modelling (WP12)

Modelling is a crucial part in every MAR scheme, as only modelling allows an outlook on the performance of a certain MAR approach in the future. In addition modelling allows assuming alternative scenarios for MAR operation, and with this enables an optimization of operation conditions ('predictive tool'). However, every model is only as good as the available data base for model calibration, and care has to be taken in the interpretation of modelling results. Therefore, this work package was intended to summarize the state of the art in modelling related to MAR and to analyse the different modelling approaches that have been followed on the different demonstration sites. With this, to the work package aims to define appropriate modelling approaches for MAR sites in general, and to prepare guidelines for the selection of appropriate MAR modelling schemes.

For the analyses of the different modelling approaches at the demonstration sites all partners contributed their modelling approaches, typically accompanied by complementary contributions and data from the laboratory scale or by modelling exercises focussing on different processes. Typically, numerical flow models based on the finite differences model MODFLOW or the finite element model FEFLOW were used for modelling. Model scales ranged from catchment scale models, e.g. in Israel, Greece and Portugal, to dedicated sub-models to analyse the subsurface processes or immediate surrounding areas of the infiltration ponds with reactive transport models (e.g. PHAST), e.g. in Israel or Spain.
For the Greek demonstration site in Lavrion, e.g. a coupled surface-groundwater model at catchment scale was developed that also incorporates the unsaturated zone. The advantage of using such models is that the exchanges between the different hydrological zones are taken into account in every time step, leading to a more accurate representation of the physical processes. The software used was the Groundwater and Surface Water Flow Model GSFLOW, developed by the USGS. The surface water part of the model is simulated using the Precipitation-Runoff Modelling System (PRMS). The watershed was divided into Hydrological Response Units (HRUs) with similar properties, depending on the lithology of the different formations (alluvium, karstified marble, and schist). The input data were mainly meteorological data (precipitation and average temperature) and data related to the soil properties of the HRUs. The time step used was daily and the simulation period included 6 years (2009-2014). Main outputs of this model included the evapotranspiration and streamflow, while other parameters such as soil storage capacity were calculated. The model was used to analyse the impact of MAR activities on the saltwater intrusion at the coastline.
For the Barcelona site at the Lobregat, a hydrochemical model was setup to study denitrification. The model code used was PHAST. This code was used both for conservative and reactive transport simulations. PHAST couples the flow simulator HST3D and the geochemical model PHREEQC-2.
Fig. 20 shows two examples of larger scale models developed for the Venetian Central Basin in Italy and the coastal aquifer at the Menashe site in Israel.

To get high-quality data on flow and transport behaviour during infiltration of water into different lithologies, a container experiment ('sandbox model') was built in the LNEC hydraulics pavilion. The sandbox is approximately 3.5 m long, 1 m wide and 2 m high (Fig. 21) and can be filled with the porous medium (soil) to be studied. The box can be divided in up to three different compartments to perform simultaneous experiments (Fig. 21). The facility is equipped with three piezometers, Teflon suction cups to sample the vadose zone, and monitoring devices such as multi-parameter probes (water pressure, pH, temperature, electrical conductivity and redox) to monitor flow and transport, both in the saturated and in the vadose zone.
In the facility various infiltration experiments have been performed and hydrochemical and hydraulic effects have been monitored. In addition, experimental results have been modelled using the numerical finite element model FEFLOW to understand flow- and transport processes in the system. The sandbox model is now available for further experimental investigations.

Based on the results of the different modelling activities at the sites and a thorough literature review, finally a white book on modelling was generated that might serve as a reference when modelling of MAR sites is required, and a visualization of the modelling activities of the MAR sites was developed through movies.

Main results achieved in the Modelling work package were (i) an evaluation of modelling activities at the different Demo sites, (ii) the development of a sandbox model that can be used to study infiltration and hydrochemical processes on MAR sites in detail, (iii) a white book on modelling with a specific focus on MAR, and (iv) visualizations of the modelling activities at the different sites.

3.3 Technical Solutions and Benchmarking (WP13)

The various potential MAR approaches and MAR targets need tailored technical solutions to meet seasonal, long-term, or emergency demands for water supply through aquifer storage. At the various demonstration sites of the MARSOL project, different technical designs have been applied and a vast experience with the operation of these implemented designs has been accumulated. Therefore one of the targets of this work-package was (i) to summarize the existing knowledge on technical solutions in MAR in general, and (ii) to analyse the technical solutions that have been applied at the MARSOL demonstration sites.

The starting point was an inventory of devices available for MAR at a global scale to create a catalogue of practical experiences. These were grouped according to the Gale classification. To these original 15 classifications, eight more were defined introducing some slight changes to existing ones (DINA-MAR, 2011). Those new devices were generally based on variations of irrigation systems in order to increase water return to aquifers from the different irrigation systems, and the implementation of MAR techniques in urban zones. The finally proposed inventory includes two new typologies (Fig. 18). The resulting data base with in total 25 different designs, that are applied partly also in the MARSOL demonstraion sites, can serve as a reference for any planned MAR activity (Fig. 22).
In addition, for each general concept, a detailed description of the requirements and advantages and disadvantages is presented, e.g. for aquifer storage and recovery (ASR), aquifer storage, transfer and recovery (ASTR), river bank scarification, or direct injection wells. As an example, the ASR method is based on injecting water during off-peak months through a borehole and the subsequent recovery during peak months through the same borehole. These devices are suitable in areas where low permeability strata overlaying the aquifer are present and when land availability does not recommend the use of dispersion techniques. As well, it requires higher quality of recharge water because it is directly injected into the aquifer and this entails energy expenditure. It may also have cost savings because of using the same device for injection and extraction.
The selection of the different demonstration sites have some important and remarkable advantages, which is (i) the various operational times of the installations, ranging from 50 years in the case of the Menashe site in Israel, to less than 3 years of operation in the case of Malta, (ii) the various water sources used, ranging from desalinated seawater in the case of Israel to treated waste water in the case of Malta, and the various technical solutions applied. This leads to a unique database that can be used to compare the different concepts and solutions.
Any MAR scheme has to be evaluated in its performance and this can be done using benchmarking tools. Benchmarking is typically based on indicators; the indicators show how a specific MAR device performs and achieves the targets it is designed for. Simultaneously, benchmarking with indicators can be used to compare MAR with other technical solutions, depending on the water management objective to reach.
Besides benchmarking based on performance indicators, also the environmental impact of an installation has to be evaluated. If, f.i. an alternative water source is used it will also have an impact on the water body that received the water originally, and it has to be ensured that ecosystem services are maintained. Higher availability of water might also encourage abusers, resulting in an increased water use that might not be justified. The MAR technical solutions have also to be communicated to potential users and the public, in order to raise awareness and acceptance. Fig. 23 shows a general matrix showing these interconnections between the benchmarking, the environmental impacts of a MAR installation, and the issues related to the technical solution.

Main results achieved in the Technical Solutions and Benchmarking work package were (i) a catalogue of different technical solutions, (ii) a detailed description of the requirements and advantages of the technical solutions, (iii) a concept for benchmarking and evaluation of different MAR schemes, and (iv) an evaluation of the different MAR demonstration sites that have been part of MARSOL with respect to their performance and benchmarking results.

3.4 Water Quality (WP14)

Quality aspects of water sources used for MAR, such as treated waste water and surface water, are of major concern in MAR system application. In particular, direct MAR methods comprise a high risk of contamination as water is applied directly into the underground. The capacity to retain pollutants in indirect MAR techniques, however, differs considerably depending on site specific hydraulic and geochemical factors.

To evaluate the water quality of potential water sources for MAR first a thorough literature search was performed. In total 152 publications were evaluated to gather information about the occurrence and environmental concentrations of synthetic micropollutants such as pharmaceuticals, personal care products, pesticides and industrial chemicals in different water sources. A comprehensive review was given for pharmaceuticals comprising 58 sub categories with 292 active substances. In addition, the database lists about 38 sub categories (fields of application) of industrial chemicals and 9 sub categories of personal care products including 87 and 32 active substances, respectively.
A major concern is the occurrence of pharmaceuticals in waste water, and, through the discharge of treated waste water, in surface water bodies. Therefore a detailed review of the occurrence of pharmaceuticals in treated waste water and surface water was performed. A total of 8996 data base entries for pharmaceuticals were found, in particular specific substance categories, namely analgesics, antibiotics, and beta blocker. Most often found are carbamazepine (antiepileptic drug) and the analgesics diclofenac and naproxen. Maximum and minimum concentrations for selected compounds found in wastewater treatment plant effluents and surface water are shown in Fig. 24.
Several micropollutants were also tested positive in the recharge water of some of the MARSOL demonstration sites. In surface water, the number of detected micropollutants ranges from 10 to 30. In treated wastewater, 25 to 35 substances were tested positive for most of the sites. Most of the micropollutants did not exceed a MEC/PNEC ratio > 1 which would indicate a possible risk for humans or the environment. However, some micropollutants were found at significant concentrations. In surface water, two substances were detected at elevated concentrations, while in (treated) wastewater it was up to five substances. According to analytical calculations, the concentrations of these substances may significantly decrease during groundwater passage. For example, for estradiol, bisphenol A, nonylphenol and fenofibrat a decrease of nearly 100% during a groundwater passage of 20 m is calculated. At a groundwater passage of 100 m, also the amounts of naproxen, diclofenac, sulfadimidin, and phenacetin decrease to insignificant concentrations.
These calculations based on field observations and on theoretical considerations are somewhat uncertain as direct verification is difficult. Therefore laboratory column experiments were conducted with soils from selected MARSOL field sites and treated waste water. Due to very low concentrations of pharmaceuticals in the treated wastewater used, some pharmaceuticals were spiked to the water that was percolated through the columns (acetylsalicyl acid, carbamazepine, diclofenac, fenoprofen, gemfibrozil, ibuprofen, naproxen, doxycycline, sulfamethoxazole, and sulfamethazine). The experiments showed that the concentrations of all of these pharmaceuticals, except of ibuprofen, decreased with depth. Sorption appears to be an important mechanism for concentration decrease with depth. Final extraction of the soil confirmed sorption, but with the exception of carbamazepine all pharmaceuticals showed also some degradation behaviour (Fig. 25).

Modelling of water quality changes during infiltration of water into the subsurface is a very valuable tool to assess the risk of certain water constituents to groundwater quality. Therefore a review of available models and also of the approached of the modelling activities at the demo sites was done. Typically, numerical or analytical models are used, such as MODFLOW, FEFLOW, SPRING, HYDROS, PHT3D or PHAST, which are coupled to geochemical models such as PHREEQC. However, selection of an appropriate model for a specific case needs careful consideration. Key questions are (i) does the model represent the key flow and transport mechanisms, (ii) what simplifications are required to represent key mechanism and how does this affect the model result (model objective), (iii) has the software been tested for similar uses, and (iv) is the software usable, e.g. what are the costs, how good is the support, how well is it tested. Typically, not one software alone fits all purposes and selection has to be done depending on the case to be covered.

Main results achieved in the Water Quality work package were (i) a catalogue of contaminants found in various potential water sources for MAR in Europe, (ii) a data base on pharmaceuticals behaviour during MAR based on column experimental results, (iii) a guideline defining water quality requirements for MAR sites, and (iv) a guideline for selecting appropriate models for contaminant fate at MAR sites.

3.5 Economic Feasibility and Benefit (WP15)

MAR, like any other economic activity, has to be economically feasible; otherwise chances for its implementation would be low. The economic feasibility of MAR projects depends upon a number of parameters affecting the costs of the project, such as capital expenses, operating costs (labour, energy, maintenance, etc.) and its revenues (the latter being mostly derived from the sales of water for a variety of uses). Besides its economic value, water has also social and environmental values that are difficult to quantify in terms of the market. This means that the benefits of MAR projects cannot and should not be based solely on the market revenues. MAR projects could improve the quality of lives of the people by several ways and, thus, the total economic value of the recharged water, which includes its abstraction value plus in-situ use and non-use values derived from groundwater being in place, should be estimated. The latter are based on people’s willingness to pay (WTP) an amount of money in order to avoid degradation of groundwater and its consequences on health, amenity, economy, etc. or their willingness to accept compensation in order to suffer the impacts incurred. The economic value to society of a good or service is the aggregate of the WTP of all individuals. It is evident that the economic value of water is not a fixed value; rather it is affected by the circumstances (e.g. scarcity of water resources due to drought or over-pumping), and individual preferences.

One aim was therefore to analyze the MARSOL demonstration projects from a socio-economic point of view by means of a cost-benefit analysis (CBA). For the scope of the project both primary and secondary approaches were used. As regards primary valuation research, a stated preference approach, namely the contingent valuation method (CVM) was applied to selected MARSOL demonstration sites, namely Lavrion (Greece), Brenta (Italy), and Algarve (Portugal). The secondary approach was based on the benefit transfer method, a common approach for completing a cost-benefit analysis.
A detailed financial analysis has been made for six out of eight MARSOL sites. Even though some of the demonstration sites have common technical features, their boundary conditions and financial characteristics are quite peculiar, therefore tailored financial analyses had to be applied to each single site. In some cases the purpose of the analysis was to figure out the financial profitability and sustainability of the project as implemented (three sites), while in some other cases it was to evaluate the hypothetical larger scale project able to reach the defined target (three sites). The demonstration sites belonging to the first group have been proven financially profitable (i.e. positive indicators) in two out of three cases, and unprofitable in one case, the demonstration sites belonging to the second group have been proven potentially profitable in two out of three cases (provided that an increase in tariffs is applied), and always unprofitable in only one case. The main reason beyond the projects’ unprofitability are in one case the high initial investment costs, in the second case the absence of direct users, i.e. the impossibility to charge someone and generate revenues. However, care has to be taken in interpreting these results, as investment costs might scale with the number of implemented installations and it is not always the intention of an installation to generate immediate revenues.
Comparing the available MAR schemes (grouped by the relevant objectives and beneficiaries) not only to the financial performance indicators (NPV, IRR), but to the related unit costs of infiltrated/recovered water (€/m3) as well reveals that the reference average cost for the life-long cost of MAR schemes referred to the quantity of managed water is between 0.15 and 0.30 €/m3, which seems to be highly competitive.
A more general MAR evaluation framework was developed to support water policy makers, water utility managers or municipal officers through the process of deciding whether a MAR solution is feasible for their specific case or not. It proposes a step-by-step procedure which is straightforward for decision making. The guiding idea is to use the Economic Net Present Value (ENPV) as a criterion to evaluate the sustainability of a solution and to use the result for a ranking, if there is more than one solution possible in the decision case. Thus, the framework can also be used to compare a MAR with a non-MAR solution. The proposed procedure is structured in 5 steps as illustrated in the Fig. 26.
This step-wise approach includes: 1) Definition of decision case: this action should set the basis for the decision case. It should clarify the problem which needs to be solved and gather all relevant information to inform stakeholders of the decision. 2) Define MAR and non-MAR solutions: an essential part of the evaluation is to define the objectives of the evaluation itself, the solutions. Those can be either one or more alternative MAR solutions (e.g. using different but for the case technically feasible recharge assets or using different sources of infiltration water) and/or non-MAR solutions technically enabling to fulfil the same objective as defined in step 1. 3) Calculate ENPV as key figure for the ranking: this step covers the calculations necessary for a well-grounded decision about the implementation of a solution. The actions to be done are mandatory in order to rank alternative solutions by their sustainability degree. 4) Apply decision rule: this step covers the formal foundation of the decision. The analyst specifies the preferences, sets the threshold(s) of the decision criteria a solution should fulfil and reviews all potential solutions for the ranking by checking if they meet the threshold(s) or not. 5) Interpret results, draw conclusions: this final step should be used to reflect and question the formal results of the applied decision rule from step 4 and draw the final decision if and which solution should be implemented. For this it is recommended to visualize the single effects composing the ENPV in a 'spider diagram'.
This framework offers a blueprint how to structure a decision case for a policy maker how to rank alternative options, especially to compare MAR solutions to non-MAR solutions. It can be applied with flexibility and tailored to the solution evaluated.

Main results achieved in the Economic Feasibility and Benefit work package were (i) an evaluation of the economics of the MARSOL field sites, (ii) a thorough calculation of costs per m3 for all sites, (iii) an economic evaluation framework for decision makers to analyse the feasibility of a MAR project, and (iv) the presentation of an example for the application of the evaluation framework aimed to the ranking of the alternative MAR and non-MAR options based on financial, economic, environmental and social assessment.

3.6 Technology Assessment and Risk (WP16)
MAR deals with very complex and multidisciplinary problems, obviously involving technical as well as non-technical (social, legal, and economic) issues. Nevertheless, a homogenized methodology is needed to assess the suitability of a site to locate a MAR facility. A proper risk evaluation involves accounting for a large number of hazards. Yet, there is a strong degree of uncertainty linked to the probability for each individual hazard and also in assessing the potential effect on a given facility by a given hazard taking place. Some uncertainties are unknown for lack of knowledge of processes or insufficient information (epistemic or systematic uncertainty). On the other hand, random or aleatoric uncertainty involve variables that differ every time an experiment is run or a measurement taken, or other variables that are not in our hands (e.g. political changes).

Main approach was therefore to develop a methodology to combine the analysis of the potential risk associated to a MAR facility in a single tool. Risk is defined in a global multidisciplinary and integrated approach. This is done by a fault tree methodology to evaluate failure in engineered systems and its application to MAR facilities, characterized by the presence of surface infiltration ponds. The main idea consists of breaking complex problems into individual (less complex) events, and evaluating the probabilities of failure of such individual events. Probabilities are then computed based on the rules provided in Boolean algebra. This method allows the introduction of multidisciplinary problems into a single common framework. With this approach one can identify the events that contribute most to the final risk estimate or those that propagate the highest degree of uncertainty throughout the system. This can then be used to invest further resources to specific events. Assessing risk in hydrological systems is an interdisciplinary field; as a result, communicating the information across interfaces between different fields in a comprehensible and efficient manner is needed, allowing decision makers to better visualize the components leading to system failure, as well as the uncertainty emerging from each subsystem.
Managing risk in a subsurface environment (groundwater) is technically cumbersome due to the difficulty of combining a large number of uncertainties associated with subsurface heterogeneities and the existence of multiple potential sources, receptors, and pathways of exposure. The probabilistic risk analysis (PRA) framework allows updating risk evaluations in a full stochastic framework, from a pre-designed and operational monitoring system. By integrating a Bayesian framework into a PRA framework based either on event trees or else on fault trees, measurements from observation wells can be used to update the probability of system failure over time. As information is added, the Bayesian interpretation of the problem allows to automatically recalibrating the probability of system failure. Risks are not only related to technical issues, but also an in-depth evaluation of the social and economic aspects involved in MAR facilities. These aspects are included in a label 'non-technical aspects' and further divided into four categories: legal constraints, economic constraints, social unacceptance, and governance. An example of the fault tree for the non-technical constraints is given in Fig. 27.

To tailor the approach to various MAR sites and designs, a survey was developed to incorporate input to fault trees in a simple and straightforward way. The aim is facilitating the analysis of risk in any given facility by visualizing all the potential hazards that could affect the operation of a MAR facility. The surveys should be filled by a user/manager of each MAR facility and the answers are related to the perception of risk associated to individual events. In such a survey, each individual potential hazard is first evaluated in a binary way, where there is a perception that this particular box in the tree (hazard) is considered relevant for a particular facility (YES/NO). If YES is selected, it should be semi-quantified as LOW, MEDIUM or HIGH risk. As perception of risk is controlled by the operational stage of the facility, two survey forms were developed, one corresponding to the design and construction operational stage, and a second one applicable for fully operational facilities. Once the survey form is filled, it is directly transferable to the tree analysis, visually allowing for a complete, fast and clear visualization of the events having the higher risk perception. Afterwards the actual risk can be obtained.

The theoretical framework is finally converted into a user-friendly, practical tool. The MAR-RISKAPP was developed using Microsoft Excel®, specifically the Developer module. This module is based mainly on the usage of Excel macros. Macros are programmed with the Visual Basic Editor (VBA) tool. The MAR-RISKAPP (Fig. 28) has been structured in four main steps (Excel Worksheets): 1) HOME, 2) INPUT, 3) RESULTS, and 4) GRAPHICAL RESULTS. When all the input sheets have been filled, the user can run the RESULTS button in order to go to the RESULTS sheet, displaying the numerical results of the risk assessment.

Main results achieved in the Technology Assessment and Risk work package were (i) development of a theoretical framework for risk assessment at MAR sites, (ii) implementing a mathematical framework for a probabilistic risk analyses through fault trees, (iii) development of easy-to-use surveys to allow site managers to generate the framework to estimate the specific risks at their site, and (iv) establishment of a practical tool based on Excel worksheets with user friendly interface for easy and automated risk assessment.

3.7 Legal Issues, Policy and Governance (WP17)

The major obstacles identified in the MARSOL project for an immediate and widespread implementation of MAR systems in the EU are to our opinion not related to technical aspects of the systems, but to water quality issues and the necessary regulatory framework. However, the Water Framework Directive (WFD, 2000/60/EC) considers artificial recharge of groundwater as one of the management tools that can be used by EU Member States for the achievement of good groundwater status. In fact, whilst listing artificial recharge as one of the basic measures to be considered by Member States in their River Basin Management Plans, Article 11(3)(f) of the Directive requires the establishment of ‘controls, including a requirement for prior authorization of artificial recharge or augmentation of groundwater bodies’. It has to be ensured that the necessary regulatory controls are in place to warrant that such practice are undertaken in a safe way which does not ‘compromise the achievement of the environmental objectives established for the source or the recharged or augmented body of groundwater’. The provisions of the WFD in this regard are directed to ensure that the necessary controls are in place to eliminate the possibility of the improper application of managed aquifer recharge schemes leading to of any degradation in the qualitative status of the receiving body of groundwater.
In this regard, Article 4(1)(b)(i) of the Water Framework Directive requires Member States to implement the measures necessary to prevent or limit the input of pollutants and to prevent the deterioration of the status of all bodies of groundwater. The Groundwater Directive then introduces the necessary provisions for making the WFD's prevent or limit objectives operational. According to CIS Guidance Document No 17, under the Groundwater Directive, substances to be PREVENTED from entering groundwater are those substances which have been identified by Member States as being hazardous. One may conclude that the substances which need to be LIMITED in groundwater, such that pollution does not occur, are all other substances.
It is also acknowledged by the Groundwater Directive (2006/118/EC) that it is technically not feasible to stop all inputs of hazardous substances, in particular the input of some minor amounts of hazardous substances which are considered to be environmentally insignificant and thus do not present a risk to groundwater. For such cases the Groundwater Directive, under Article 6(3)(d), introduces a series of exemptions. Artificial recharge is considered as one of these exemptions. The CIS Guidance Document 17 provides an interpretation of this prevent and limit concept. According to this EU Guidance Document, therefore to PREVENT an input into groundwater therefore means: Taking all measures deemed necessary and reasonable to avoid the entry of hazardous substances into groundwater and to avoid any significant increase in concentration in the groundwater, even at a local scale. It is understood that these measures can include source water quality and flow control mechanisms and upstream treatment of the recharge source water.
The prevent and limit conditions, however, are also a requirement of the Water Framework Directive under Article 4(1)(b)(i). The Groundwater Directive under Article 6(3)(d) introduces an exemption for Artificial Recharge schemes, permitted under Article 11 of the WFD, from the prevent and limit requirements introduced under the Directive’s Article 6(1). The fact that Article 6(3)(d) of the GWD required a permit that was issued under the WFD implies that the permit should in itself already give due consideration to the WFD's prevent and limit objectives. It is felt that this is a grey area between the two Directives, which can potentially give rise to interpretation conflicts.

Given the significant potential of MAR as an additional option for water resources management, the MARSOL project is therefore proposing a regulatory framework which can commonly be used in EU Member States to ensure that MAR schemes are implemented in line with the requirements of the EU environmental legislation. The proposed framework interprets the ‘prevent and limit’ requirements introduced under the Water Framework Directive in the light of the interpretation developed under the Groundwater Directive.
This proposed regulatory structure, which is schematically illustrated in Fig. 29, is based on the following principles: (i) the undertaking of a risk assessment to determine the potential adverse impacts which could arise as a result of the MAR scheme on the status of the body of groundwater; (ii) the establishment of control mechanisms to ensure the reliable performance of the MAR scheme; and (iii) monitoring of the performance of the MAR scheme and its impact on the augmented body of groundwater.
This three-tiered assessment structure has also been developed with the aim of harmonising and integrating the regulatory requirements of the Water Framework and the Groundwater Directive with the Environmental Impact Assessment Directive. The proposed regulatory assessment can be considered as an Environmental Impact Assessment tailored for MAR schemes. This approach further extends the application of the Water Framework Directive's environmental objectives to groundwater bodies.
Each assessment level under this scheme includes a number of decision levels which must be addressed in the MAR scheme evaluation process. The technical protocols to enable the compliance assessments at each decision level have been developed based on the results of the project's horizontal work packages which focused on the following issues: (i) investigation and monitoring, (ii) numerical groundwater modelling, (iii) water quality, (iv) economic feasibility and benefits, and (v) technology assessment and risk.
It is therefore suggested that a regulatory framework based on risk assessment, control mechanisms and monitoring has to be established as a tool which can facilitate the interpretation of the requirements of the Water Framework and Groundwater Directives in relation to MAR. We recommend that a specific action on MAR technical solutions should be established under the WFD CIS to provide clear guidelines to Member States on the application of MAR techniques, as it was tested in their 3rd River Basin Management Plans, in line with the requirements of the Water Framework and Groundwater Directives.

Main results achieved in the Legal Issues, Policy and Governance work package were (i) a thorough analyses of the EU regulatory framework related to water resources management, (ii) interpretation of the framework in relation to MAR, (iii) a proposal of a regulatory framework to enable the proper implementation of MAR, and (iv) to establish a specific action on MAR technical solutions under the WFD CIS to provide guidelines to member states.

Potential Impact:
Addressing water scarcity, including new water stress imposed by climate change, implies a huge and combined effort from the industry, science, and society to put into practice new innovative and sustainable development approaches and solutions based on the systematic use of non-conventional water resources, by recycling and reusing water, to attain a better balance between water demand and water availability.
Water scarcity is already affecting at least 11% of the European population and 17% of EU territory. Furthermore, growing population, whether permanent or temporal such as tourists, industry, agriculture and aquaculture, are negatively affecting water resources due to overexploitation and inadequate land use, leading to groundwater resources depletion and pollution. In a 'business as usual' scenario, water consumption by the public, industry and agriculture would increase by 16% by 2030. Water consumption patterns (e.g. in agriculture) are also likely to change in response to climate change, contributing to a further decrease in water availability. Innovative, available and affordable solutions must be found to adapt to water scarcity, through demand and supply management, while decreasing energy needs, rehabilitation costs, and improving water quality throughout the EU. In short, adaptive management policies must lead to improved water availability and quality, in a more efficient way, with lower economic, social and environmental costs.

MARSOL's main immediate and future impact is the promotion of the generalized use of MAR creating new worldwide market opportunities for this technical solution. With this it aims to increase the water resources availability by means of storing water, through recycling, reuse and from periods of excess, to be recovered in periods of scarcity.
Improving the integrated and sustainable management of water resources and ecosystems, MAR will advance the potential of water reuse, due to water quality improvement during aquifer transport and storage. It can also be highly effective in counteracting salinization of coastal aquifers, an EU-wide phenomenon. This means that MAR can play an important role in a more rational and efficient water resources management.
However, although MAR can be a key solution to Europe's water crisis, its application in the EU is rather limited to date. This is due to a mix of factors, including public perception, health risks, regulation, policy objections, availability of other water supply options, although they may be unsustainable (e.g. aquifer over-pumping) or energy intensive (desalination). Therefore, we propose a multistep approach, in which a sound technological basis is linked to a viable business case, and to an understanding of the social dimensions of MAR, including public acceptance and governance frameworks. Through this approach, MARSOL may have achieved a perception change among economic sectors, policy makers, scientists and the general public, leading to a more open attitude with respect to MAR, advancing its consideration as a viable water option throughout the EU and influencing water resources management in other regions. This is supported by the fact that the large variety of demonstration sites with different water management problems and MAR objectives and approaches demonstrated the viability of this technique for many different water availability problems, not only in Europe but also in other regions in the world affected by water scarcity and drought.
Strong emphasis was therefore put in the creation of a knowledge base that can effectively contribute to more adequate decision making, where social and economic benefits for different key societal sectors are clearly stated. This knowledge-base will inform future decisions of stakeholders, actors, and SMEs on the practicable MAR demonstrated options in new areas. It is built in close connection with the beneficiaries and the local authorities, so they can contribute to understand and consider the adaptation measures and the contribution MAR can make to economic and social development, as well as to ecology.
The direct beneficiaries of MAR solutions are the industrial water sector users and water suppliers, which can rely on improved water availability. These include farmers, water suppliers, industry, society and combined partnerships. The job creation potential and competitive advantage for EU industry will rise (i) from the development of a new market, for industry and SMEs, on MAR technical solutions capable of delivering the appropriate response to the increasing water needs, and also (ii) from the competitive opportunity created for the water users from the increase and reliability of water source, in terms of quantity and quality.

The major obstacles identified in the MARSOL project for an immediate and widespread implementation of MAR systems in the EU are to our opinion therefore not related to technical aspects of the systems, but to water quality issues and the necessary regulatory framework. The overall number of contaminants identified in surface waters and especially in treated wastewater (84 organic micropollutants, including 52 human pharmaceuticals, 24 industrial chemicals, 5 food additives and 3 pesticides) are having a serious impact on the applicability of MAR for such water sources as well as on the public acceptance of MAR measures. Although it was demonstrated at several sites (e.g. at the Llobregat site in Barcelona) and in laboratory experiments that natural degradation processes are effective for some of the contaminants, other compounds are recalcitrant even under optimized infiltration schemes (e.g. diclofenac, carbamazepine). These findings collide with the Water Framework Directive (WFD) that does not allow a deterioration of groundwater quality but asks for quality improvements.
Therefore a regulatory framework was developed that is based on risk assessment, control mechanisms and monitoring, as a tool which can facilitate the interpretation of the requirements of the Water Framework and Groundwater Directives in relation to MAR. We recommend that a specific action on MAR technical solutions should be established under the WFD CIS to provide clear guidelines to Member States on the application of MAR techniques, as it was tested in their 3rd River Basin Management Plans in, line with the requirements of the Water Framework and Groundwater Directives. This should finally enable a more widespread implementation of MAR schemes in the Member States as the implementation can be based on a solid regulatory framework.

Training activities are one of the major dissemination activities of the MARSOL project. They aim at bridging the knowledge gap between the technology developers and researchers and the actual users of the technologies. The success of the project relies substantially on the conducted training activities. The training activities are based around the eight demonstration sites of the project. A preliminary schedule of events was passed at the project's kick-off meeting and was re-discussed and adapted throughout the course of the project. The workshops were coordinated with other project meetings and external events such as major European and non-European conferences. Figure 30 shows the final status of the meetings and workshops schedule for the whole project lifetime. The following dissemination and training workshops have been successfully conducted during the project:
- Managed Aquifer Recharge in the Arenales Areas - MAR4FARM: Workshop October 2014, Santiuste de San Juan Bautista and Gomezserracín, Segovia, Spain: Two one-day workshops, addressing especially farmers and the population in general living in these rural areas. The irrigation communities collaborated actively in the workshops. The workshops were organized by Partner No 4 Tragsa.
- MAR-SAT Expert Forum: Workshop: December 2014, Tel Aviv, Israel. The MARSOL project meeting in Tel Aviv early December 2014 was followed by a two-day joint workshop of the MARSOL and DEMOWARE EU projects, focussing on experiences and issues of soil-aquifer treatment (SAT). The two-day workshop showed a lot of synergies and provided an excellent forum for networking and laying the ground for further new projects. The workshop was organized by Partner No 8 Mekorot.
- Technical Solutions for Managed Aquifer Recharge - MARenales: Workshop, March 2015, Coca and Gomezserracín, Spain: MARSOL members working in the field of water management in large irrigation areas have shared their expertise with regional stakeholders as well as other experts from the MARSOL project and invited experts from Korea and from the Spanish Geological Survey. The workshop had two sessions, one project-internal session and one open session involving farmers from the irrigation community and other end-users. Sessions were held in Coca Castle (Segovia), and Gomezserracín (Valladolid). The field trip, apart from visiting MAR facilities, included visits to agro-industries related to MAR, such as a vegetables packaging and exportation factory. The workshop was organized by Partner No 4 Tragsa.
- Advantages of using Numerical Modelling in Water Resources Management and Managed Aquifer Recharge Schemes: Workshop April 2015, Pisa, Italy: International workshop on numerical modelling of hydrological processes and groundwater flow and solute transport in aquifers, held in synergy with the new EU HORIZON 2020 project FREEWAT ("Free and Open Source Software for Water Resource Management"). About 130 persons attended the free workshop, both from the academy and the professional world. The workshop was organized by Partner No 7 SSSA.
- Water Quality Aspects of Managed Aquifer Recharge: Workshop, June 2015, Faro, Portugal: The workshop focused on research results, practical experience, and innovative ideas related to water quality issues in MAR activities, contributing to the training of project participants' staff and researchers as well as other stakeholders in the water sector such as industry/SMEs, authorities, and end users. The workshop addressed changes and associated risks in the chemical status and hydraulic properties of water bodies due to infiltration of various water sources in MAR installations. The workshop was organized by Partner No 3 LNEC.
- Legal Issues, Policy and Governance: Workshop, October 2015, Luqa, Malta: The overall objecttive of the workshop was to discuss the development of the MAR Regulatory Framework under the MARSOL Project. In particular, the scope of the workshop was to engage policy makers, regulators and site operators in a discussion on the practical application of the proposed MAR Regulatory Framework and thus address any identified implementation gaps. A draft Regulatory Structure for MAR developed under Work Package 17 and the contribution of the Project’s Horizontal work-packages to the development of the specific regulatory tests were presented. Afterwards, the workshop discussed the application of the MAR Regulatory Structure to each of the MARSOL demonstration sites. The workshop was organized by Partner No 23 SEWCU (Malta).
- Investigation and Monitoring Techniques in MAR: Workshop, March 2016, Lavrion, Greece: The workshop covered wide aspects of environmental monitoring technologies, focusing on hydrologic and water quality parameters that are crucial for Managed Aquifer Recharge facilities. The above aspects were examined through an integrated approach, including new monitoring technologies, commercial monitoring technologies that are cost and energy effective, data gathering, transmission, management & storage, and critical environmental parameters in groundwater engineering (with respect to MAR facilities). The workshop was organized by Partner No 2 ICCS (Greece).
- Water to Market: Financial and Economic Analysis of MAR Solutions: Workshop, June 2016, Venice, Italy: The participants gained awareness of the actual costs (overall and unitary costs) of the demonstration sites MAR facilities, of the opportunity to recover them selling the “managed” water and of the general benefits that can justify a MAR investment regardless its actual financial profitability. The workshop was complemented by the participation to COWM2016 - International Conference on Citizen Observatories for Water Management, Venice, 7-9 June 2016. The workshop was organized by Partner No 6 SGI (Italy).
- Managed Aquifer Recharge - Water Quality and Reactive Modelling: Advanced Study Course (ASC) for Young Scientists November 2016, Barcelona, Spain: The Advanced Study Course was intended for graduate and post-graduate students, PhD students, and postdocs in the fields of geosciences, water research, environmental research, or related areas; it was also directed at professionals aiming at improving or broadening their qualification. Incorporating a field site visit and modelling exercises, the course had a strong combination of theory and practise. The class was filled with interactive contributions which increased awareness and technical knowledge of managed aquifer recharge solutions in different countries and settings. The Advanced Study Course was organized by Partners No 1 TUDa (Germany) and No 5 UPC (Spain).

The workshops were major showcases for the work of MARSOL. They also proved to be a useful tool for networking with other European projects such as DEMOWARE, DEMEAU, FREEWAT and others. The workshops generally included a field component, i.e. visit of the project's demonstration sites and other related water management facilities (water works, WWTPs). Members of MARSOL's Expert Advisory Panel were invited to the workshops to attend and give key-note presentations.
Through the workshops, MARSOL was able to reach out to local and regional stakeholders such as water authorities, water utilities, regional authorities, environmental associations, and other interested pro¬fessionals or the interested general public as well as students. The Advanced Study Course trained students from all over the world with very different background, helping to increase awareness and technical knowledge of managed aquifer recharge solutions.
The schedule of the workshops was to some extent influenced by external factors such as large conferences (e.g. EGU, IAH) or the availability of venues. However, all workshops could also be used for project management purposes, being accompanied by Steering Group or Core Group meetings.
Such workshops, but also specialized courses directed at graduate students and young scientists, have proven to be a most useful tool for 'spreading the message', for exchanging ideas, and for networking. If included in research or demonstration projects, they should be given a substantial amount of resources to facilitate their successful organization at all levels, including preparation, advertisement, venue, catering, and documentation.

In addition, main results of the MARSOL project were published in peer reviewed journals (17, a similar number is either in review or prepared for publication) and presented on scientific conferences (47). With this, a large audience in the scientific community was reached and MARSOL was well visible through these activities. For exploitation of the results 45 different approaches, measures, and documents could be identified, that are further explained in Section 4.2 of the final report.

List of Websites:
www.marsol.de

Contact:
Prof. Dr. Christoph Schüth
Technische Universität Darmstadt
Institute of Applied Geosciences
Schnittspahnstrasse 9
64287 Darmstadt
Germany
Phone: +49 (0) 6151 16 22090
Fax: +49 (0) 6151 16 23601
E-mail: schueth@geo.tu-darmstadt.de

Final Report Summary - MARSOL (Demonstrating Managed Aquifer Recharge as a Solution to Water Scarcity and Drought)

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