MARSOL White Book on the state of the art in Managed Aquifer Recharge Modelling. A Literature Review.

Abstract

In the context of Managed Aquifer Recharge (MAR) numerical modelling, an important process with many applications such as the prediction of rise of groundwater mounds, to determine where groundwater must eventually be pumped, to understand quality changes in infiltration water and aquifer water, to predict the success of treatment induced by MAR methodologies or to calculate the necessary injected volumes to counter a saltwater intrusion problem. It is essential, as a state of the art overview, to compile several applications in different demo-areas and scales, where modelling was essential to refine artificial recharge strategies and to help understanding the main impacts of a MAR project. The main objective of the EU INNO-DEMO FP7 project MARSOL was to demonstrate that 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 through storage of excess water to be recovered in times of shortage. MARSOL operated 8 demonstration sites in 6 countries around the Mediterranean (Portugal, Spain, Italy, Greece, Malta, Israel) applying various technologies i.e. infiltration ponds, river bed infiltration, direct injection wells, river bank filtration, to infiltrate various water sources, i.e. river water, surface runoff, treated waste water, desalinated sea-water. More information can be found in www.marsol.eu and in Costa et al (2015) (https://www.researchgate.net/publication/275716406_Modelling_Contributions_of_the_Local_and_Regional_Groundwater_Flow_of_Managed _Aquifer_Recharge_Activities_at_Querenca-Silves_Aquifer_System), regarding Querença-Silves aquifer system in Portugal. One of the outputs of MARSOL project was the “White book on MAR modelling: Selected results from MARSOL PROJECT”, cf. Lobo-Ferreira et al (2016) available in https://www.researchgate.net/publication/314957907_White_book_on_MAR_modelling_Selected_results_from_MARSOL_PROJECT. This oral presentation will address the state of the art of modelling methodologies and tools in Managed Aquifer Recharge, both in flow and transport model applications. Following MARSOL literature review for MAR modelling, the main conclusion, considering that for every model there is a different set of input data required, so one of the most important factor in selecting the appropriate model to a specific area/study is to verify what data is available/obtainable in order to feed it as much as possible allowing it to produce reliable results. Used models vary, but finite difference MODFLOW base software seems to be by far more frequently used, both due to be easily available and well documented, there are several programs adapted to specific problems. Due to its complexity finite elements are not so abundantly used, although the FEM grid is far more adjustable to complex limits of study areas. On the other hand, FEM HYDRUS was commonly selected for simulations in vadose zone. In hydrogeochemical studies related to MAR, PHREEQC based software was the most used, mostly due to its very wide set of capabilities concerning not only speciation simulation but also transport. Aquifer and local (small area of the aquifer) seems to be the most common scales studied. Small scale models (infiltration basin or aquifer sandbox model recreation) are scarce. MAR modelling, at a large scale, has been used as a decision support tool as basis to decide the suitability of MAR methodologies, most effective measures of environmental problem containment and to explore scarcity scenarios. Local scale modelling efforts have been developed during MARSOL project in order to determine the infiltration capacity of the injection well, the aquifer’s local hydraulic properties and the direction and residence time of the injected water. At a local scale event, local hydraulic parameters are determined with the support of analytical methods, such as conventional pumping test analysis techniques. To support the local scale analysis and modelling of the well injection tests, resistivity profiles using dipole-dipole array were performed before, during and up to 4 days after an injection test with salty water as a tracer with the goal of gathering more information regarding water pathways in the area with the time lapse evolution of the resistivity, though a low variation of resistivity with time was achieved. Also in de numerical modelling context, MARSOL Deliverable 12.2 “GIS database of the MARSOL DEMO Sites” aimed to prepare GIS layers of information for conceptual modelling for selected MARSOL sites. This activity was developed to produce the structure of a GIS database that is able to accommodate main available information of the Demo sites, concerning background information as the conceptual groundwater flow model, water budgets under actual and climate change projected situations, vulnerability indexes, infiltration indexes, field tests, already existing data concerning geology, soil, land cover, aquifer information, river basins, streams, natural and artificial reservoirs, etc. Besides information for conceptual modelling the GIS database was also structured to contain the MAR facilities, infrastructures and also some related monitoring information. Besides the information available in the MARSOL website and https://www.eip-water.eu/MAR_Solutions further reasoning on Modelling in Water Resources and on MAR is in https://www.southasiawaterinitiative.org/sites/sawi/files/WRS%20SAWI%20reportjune8.pdf#page=57.