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The agricultural production in coastal environments is challenging. In the low-lying farmlands along the Venice Lagoon, Italy, saltwater intrusion that naturally occurs in coastal environments is exacerbated by land subsidence, seawater encroachment along the main watercourses, peat oxidation, and peat-driven salinity. Sea level rise expected in the next decades will intensify seawater contamination, enhancing the threats for crop productions. In this context, mitigation strategies are fundamental to avoid the loss of agricultural land. To this end, a test of freshwater recharge through a ~200-m long buried drain was conducted in an experimental field located at the southern margin of the Venice Lagoon. The soil is mainly silt-loam with the presence of acidic peat and sandy drifts. The drain was installed in 2021 at 1.5 m depth along a sandy paleochannel crossing the area in southwest to northeast direction. It supplies the Morto Channel freshwater to the farmland taking advantage of the high hydraulic conductivity of the sandy soil and the 2-m elevation difference between the channel water level and the farmland surface. The drain was tested at the end of the 2021 maize growing season, from August, 2nd until September, 7th. Five monitoring stations were installed and equipped with a 2.5 m deep piezometer to monitor depth to the water table and electrical conductivity (ECw) and TEROS 12 (METER Group, Inc., Pullman, WA, USA) soil moisture, electrical conductivity (ECb), and temperature sensors installed at four depths (0.1, 0.3, 0.5, and 0.7 m). Three of those stations were placed along the paleochannel (S1, S2, S3), while S4 and S5 were placed outside about 30 m away. Moreover, six additional piezometers were placed at 5, 10, and 20 m from both sides of S2 station to monitor the lateral spread of freshwater supply. Stations S1 and S2 were also equipped with electrical resistivity tomography (ERT) lines crossing the recharging infrastructure. The ERT lines were 14.4 m long, electrode spacing was 0.3 m and the resistivity electrode array was dipole-dipole, obtaining a maximum depth of investigation equal to approx 2.5 m. Data were collected on five dates, two before (7/12 and 7/30) and three after the drain opening (8/10, 8/20, and 9/7). The freshwater supplied to the farmland caused an increase of resistivity at both S1 and S2, with higher resistivity differences between dates at S1, suggesting a certain effectiveness of the implemented recharge solution. The ECw measurements carried out in the piezometers show a highly variable response during the test, however ECw increased after drain closure at all piezometers. On the contrary, the effects on soil water content and ECb was negligible. The effectiveness of the strategy will be tested more deeply during the 2022 maize growing season by monitoring the effects of freshwater supply on plant stress and final crop yield.

Tidal marshes are coastal landforms daily flooded by sea water. Their fate is strongly conditioned by the future relative sea level rise, intrinsically linked to climate change. The significant ecological and socioeconomic value of these ecosystems is a compelling reason to improve our understanding of marsh platform dynamics relative to the mean sea level. Among various factors influencing the elevation of these depositional landforms, sedimentation and compaction of the marsh body itself play a major role. In particular, it has been observed that marsh soils undergo large autocompaction due to high porosity and compressibility. Hence, characterization of marsh geomechanical properties is of paramount importance to develop reliable long-term predictions. With the aim of characterizing the geomechanical features of tidal marshes in the Venice Lagoon (Italy), a campaign of in-situ loading experiments has been recently carried out. In each experiment, eight 500-l tanks were cyclically filled and emptied with lagoon water, applying loads of various duration and entities on marsh platform. A monitoring system, based on pressure and displacement transducers, tracks the marsh response to the applied loads. This work describes the modeling activities developed to interpret these measurements from the in-situ experiments. The simulations have been carried out using a 3D poro-mechanical model solving Biot’s equations by a mixed finite-element formulation. A power law is used to describe the soil compressibility vs effective stress relationship, and main parameters are initially defined based on oedometric tests carried out on a few samples cored from the marshes. Mechanical hysteresis is also accounted for. The model calibration allows to satisfactory match the available pressure and deformations records. In particular, the numerical simulation accurately accounts for the behavior of (vertically) heterogenous marsh deposits as revealed by core interpretation. Based on these promising results, we are looking towards using the calibrated constitutive relationships in long-term biomorpho-geomechanical analyses, to forecast the fate of the marshes in the Lagoon of Venice.

Estudios recientes ponen en manifiesto la vulnerabilidad de las cuencas del mediterráneo y las limitaciones de los actuales organismos gestores para mantener un desarrollo sostenible de los recursos hídricos subterráneos. Con el fin de abordar esta problemática, en este trabajo se han investigado los principales inconvenientes relacionados con la gestión de agua subterránea, teniendo en cuenta la perspectiva de las partes implicadas mediante la realización de encuestas. Para llevar a cabo esta investigación, se han seleccionado cuatro cuencas mediterráneas representativas que se encuentran actualmente bajo estrés hídrico: el acuífero costero de Comacchio (Italia), el acuífero del Alto Guadalentín (España), el acuífero aluvial de la cuenca del río Gediz (Turquía), y el acuífero de Azraq (Reserva de humedales de Azraq, Jordania). Los resultados revelan el punto de vista de las partes implicadas, relacionado con la gestión actual de los sistemas acuíferos y su experiencia con las herramientas disponibles para la gestión de las aguas subterráneas, como lo son las redes de monitoreo y los modelos numéricos. El análisis realizado y ha permitido identificar algunas peculiaridades y retos en común en las cuatro áreas de estudio. Uno de estos grandes desafíos es la falta de referencias para evaluar la adecuación de la red de monitoreo en relación con la frecuencia de muestreo y la distribución espacial. La metodología aquí propuesta junto con los resultados será útil para valorar la percepción de las partes implicadas en otros acuíferos que presenten una situación similar. El presente trabajo está basado en la investigación realizada por (Bonì et al., 2022) llevado a cabo en el marco del proyecto RESERVOIR: (sustainable groundwater RESources management by integrating earth observation deriVed monitoring and fOw modelIn Results), financiado por el programa Partnership for Research and Innovation in the Mediterranean Area (PRIMA) apoyado por la Unión Europea (Acuerdo de subvención de 1924; https://reservoir-prima.org/).

Land subsidence severely threatens most of the coastal plains around the world where high productive industrial and agricultural activities and urban centers are concentrated. Coastal subsidence damages infrastructures and exacerbates the effect of the sea-level rise at regional scale. Although it is a well-known process, there is still much more to be improved on the monitoring, mapping and modeling of ground movements, as well as the understanding of controlling mechanisms. The International Geoscience Programme recently approved an international project (IGCP 663) aiming to bring together worldwide researchers to share expertise on subsidence processes typically occurring in coastal areas and cities, including basic research, monitoring and observation, modelling and management. In this paper, we provide the research communities and potential stakeholders with the basic information to join the participating teams in developing this project. Specifically, major advances on coastal subsidence studies and information on well-known and new case studies of land subsidence in China, Italy, The Netherlands, Indonesia, Vietnam and Thailand are highlighted and summarized. Meanwhile, the networking, dissemination, annual meeting and field trip are briefly introduced.

The Vietnamese Mekong Delta was formed by rapid transgression during the second half of the Holocene by deposition of mainly unconsolidated, fine-grained (clayey) sediments undergoing high compaction rates. The natural subsidence can seriously impact the already vulnerable delta plain as its low elevation exposes the delta to global sea level rise, flooding, salinization. Human activities such as groundwater pumping, infrastructural loading, sand mining and dam construction have exacerbated the effects of natural consolidation. Here we present a novel modeling study that has allowed to reproduce the formation and evolution of the Mekong delta over the past 4000 years. Using an adaptive finite-element mesh, the model properly simulates accretion and natural consolidation characterizing the delta evolution. Large soil grain motion and the delayed dissipation of pore-water overpressure are accounted for. We find that natural compaction of Holocene deposits following delta evolution exceeds predicted values of absolute sea level rise. The unprecedented high rates (up to ~20 mm/yr) threaten the lower delta plain with permanent inundation and inevitably reduce the designed service life of flood defense structures along the coast. Total subsidence and sediment delivery to the delta plain will determine its future elevation and vulnerability to relative sea level rise.

A widespread concern among the scientific community is the increase of the greenhouse gas emissions, especially CO2, which may yield an increase of earth's temperature. To reduce the CO2 released in the atmosphere an option which is attracting a growing attention is its sequestration in deep geologic formations. Deep saline aquifers may offer a great potential for the storage of large volumes of carbon dioxide. However, because of the relatively small practical experience with CO2 disposal in brine formations, more research is needed to assess the feasibility of the operation. In particular more studies are needed to identify aquifers sealed by continuous clay caprock over a regional scale. For this reason it is important to study the heterogeneous character of the sealing layers, i.e., the probability of having small fractures or zones of high permeability in the aquitards. In this paper we try to evaluate the effects of these potential heterogeneities on a CO2 sequestration problem. Aquitard properties are generated using a stochastic approach based on the binary field generation so that higher permeability inclusions are produced in the caprock with a given distribution. Montecarlo simulations are then needed to calculate the probability distribution of the escape of CO2 through a sequence of aquifer/aquitards that are representative of the Upper Adriatic system. Stochastic modeling appears to be a very powerful tool to take into account in a CO2 sequestration project the degree of continuity of the sealing aquitards. This issue is of importance to understand how potential discontinuities in the caprock can affect the upward migration of the injected carbon dioxide and to quantitatively assess the risk related to possible CO2 escape to the ground surface.