Geophysical Characterization of Hydraulic Properties around a Managed Aquifer Recharge System over the Llobregat River Alluvial Aquifer (Barcelona Metropolitan Area)

Alex Sendrós,Mahjoub Himi,Aritz Urruela,Ruben Garcia-Artigas,Albert Casas,Raúl Lovera,Lluís Rivero

doi:10.3390/w12123455

Abstract

Managed aquifer recharge using surface or regenerated water plays an important role in the Barcelona Metropolitan Area in increasing storage volume to help operators cope with the runoff variability and unexpected changes in surface water quality that are aggravated by climate change. The specific aim of the research was to develop a non-invasive methodology to improve the planning and design of surface-type artificial recharge infrastructures. To this end, we propose an approach combining direct and indirect exploration techniques such as electrical resistivity tomography (ERT), frequency domain electromagnetics and data from double-ring infiltration tests, trial pits, research boreholes and piezometers. The ERT method has provided much more complete and representative information in a zone where the recharge project works below design infiltration rates. The geometry of the hydrogeological units and the aquifer-aquiclude contact are accurately defined through the models derived from the interpretation of ERT cross-sections in the alluvial aquifer setting. Consequently, prior to the construction of recharge basins, it is highly recommended to conduct the proposed approach in order to identify the highest permeability areas, which are, therefore, the most suitable for aquifer artificial recharge.

Highlights

The Barcelona Metropolitan Area has a drinking water demand for almost three million inhabitants, its sources of water are scarce because of its Mediterranean climate
Two complementary geophysical methods were applied in order to perform the characterization of lateral and vertical lithological variations of the saturated zone (SZ) below the infiltration pond: Electrical resistivity tomography (ERT) and frequency domain electromagnetics (FDEM)
The design of geophysical surveys and the selection of the multi-electrode arrays was planned considering the depth of investigation, the length and resolution required and the expected structure derived from hydrogeological background knowledge

Summary

Introduction

The Barcelona Metropolitan Area has a drinking water demand for almost three million inhabitants, its sources of water are scarce because of its Mediterranean climate. Many European rivers have fairly constant flows > 1500 m3 /s, but Mediterranean rivers are characterized by their low average flows with intermittently high flow peaks, such as the Llobregat River (22 m3 /s of annual average flow but with a 2–5 m3 /s flow most days of the year) In addition to this water scarcity, the management of drinking water in the Mediterranean area has, some other extra difficulties in comparison with other areas in Europe, such as the industrial impacts, the pollution, the wastewater management, changes in land use and the demand of a minimum ecological flow in the context of the Water Framework Directive. Good management integrating all possible sources of water in the Barcelona Metropolitan Area is required [1].

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