A MULTI-HAZARD APPROACH IN THE DESIGN OF A HYDROGEOCHEMICAL MONITORING NETWORK: THE STRAIT OF MESSINA (ITALY) CASE.
The Strait of Messina (hereafter SoM), separating Sicily from continental Italy, is prone to different geohazards, including energetic seismicity, as the 1908 M 7.1 Messina-Reggio Calabria earthquake. Climatic changes pose further treats, caused by the intensification of rainfalls, which modifies the runoff/infiltration ratio, fostering the pauperization of groundwater bodies, and sea level rise, causing the salinization of coastal aquifers. The landscape of the SoM area is the result of a capillary interdigitation of natural and built environments, where changes affecting the former could generate profound perturbations in the latter, and vice versa.
Landscape management requires here the development of efficient environmental monitoring networks, including hydrogeochemical ones. Their implementation in the SoM area is one of the aims of the Work Package 5 “NEMESI” of the Italian post Covid-19 pandemic PNRR project “MEET”, financed in the framework of the European Next Generation EU initiative and leaded by the Italian National Institute of geophysics and Volcanology (INGV).
The strategy for designing the hydrogeochemical network has been developed through the following steps: i) Only parameters potentially influenced by the different hazard-generating processes acting in the SoM area have been selected, excluding those for which no efficient, or too much expensive (for the project budget) sensors are presently available, II) Geological, geomorphological, hydrogeochemical and seismic data have been analysed, also applying geostatistical tools, for extracting a first general list of potential sites (springs, wells, piezometers, drainage galleries, surface water bodies) candidate to host the network iii) All sites affected by unsurmountable logistic (absence of mobile network coverage for data transmission, impossibility of building structures hosting the instrumentation, etc.) and/or administrative (time to obtain permission of using the site not compatible with the project deadline) limitations have been excluded; iv) The remaining sites have been equipped with low cost dataloggers, integrated by periodic surveys, for verifying that, over a complete hydrological year at least, the recorded variations were compatible with the network aims: presence of transients emerging over a pure seasonal cycle.
After the preliminary monitoring, the final list was extracted, preferring sites where variations of one or more physic-chemical parameters should represent a proxy of one or more hazard-generating processes. Some examples are: i) changes in water electrical conductivity due to saline wedge intrusion, ii) variations of temperature and piezometric levels induced by permeability changes driven by seismic and aseismic deformations, iii) changes in oxygenation, turbidity and dissolved CO2, which can be controlled by both eutrophication and mixing with deep volatiles, whose flux is driven by neotectonic activity.
The final aim is producing open access data of interest for the different stakeholders, including, but not limited to, the scientific community, the local shellfish food industry, urban planners, water companies, public agencies, general contractors involved in civil infrastructures construction.