This project (MD3_UPC) is a subproject of MD3, whose overall goals are to advance towards (1) estimating nutrient fluxes to the sea by submarine groundwater discharge (SGD), which is essential for marine ecosystems, (2) understanding and controlling seawater intrusion (SWI), which threatens most coastal aquifers, and (3) understanding geochemical processes in the mixing zone between discharging freshwater and intruding seawater. To this end, we have made significant progresses both on the characterization of SWI (notably, we have developed a singular pilot site at Argentona, some 40 km NE of Barcelona) and on the modeling of mixing processes. Specifically, we have developed innovative methods for characterizing coastal aquifers (cross-hole resistivity tomography, thermal tests, new interpretation methods for Ra and Rn data, and for hydraulic tests) and for describing transport through heterogeneous media. But in the process we have met numerous surprises, to the point that we have challenged the traditional SWI paradigm (e.g., we have explained the frequent anomalies of salinity profiles, why they may be misleading and why the conventional representation of SWI may not be valid in realistic heterogeneous aquifers). These surprises have delayed meeting the global project goals, which is why we propose to advance along three directions: consolidating the emerging SWI paradigm by new characterization methods, developing new techniques for identifying SGD, and search for indicators of SWI and SGD that can be applied by water management agencies on a regular basis.
In this context, MD3- UPC subproject will be responsible for modeling, for field experiments, and for the extension of SGD and SWI to regional scale. In the modeling WP, the main challenge will lie on the representation of the intense dynamics of the multilayered mixing zone which we will attempt both with existing codes and with the newly developed effective transport formulation. In the field, we will attempt innovative methods for characterizing SGD and SWI. Specifically, we will emphasize new monitoring systems (induction logging for salinity, continuous recording of pressure, geophysical characterization of SGD by off-shore ERT and by thermal imaging of the sea floor and the surface). We will also lead the search for large (regional) scale characterization using tools that can be used by water (both continental and marine) management agencies.
To this end, we will investigate the possible use of microbial communities as indicators of mixing, SWI dynamics and/or SGD, off-shore ERT to identify zones of freshwater discharge, and thermal imaging using drones and Landsat 8 in cases (periods) of high contrast between fresh water and sea water temperature.
Funding: Agencia Estatal de Investigación (AEI)
Reference: PID2019-110212RB-C21
Total amount: 182.710 €
