Modelling groundwater flow in carbonate ridges: the case of m. Paganuccio and Cesane (Italy)

Carbonate aquifers, 3D steady state flow model, hydrogeological budget

Best tracer selection for hydrogeological investigations: preliminary results from laboratory test

Tracers techniques are a good tool to investigate groundwater dynamics; they are essential to perform measurement of hydrogeological parameters of aquifers. This study was aimed at characterizing adsorption, effective porosity and pore water velocity in soil samples collected in a hydrographic basin of Marche Region (Italy). This basin has the typical geologic and hydrogeological features of many basins in Central Italy. Therefore. the principal aim is to evaluate the best tracer to be used for hydrogeological purpose (i.e. groundwater tracer test and aquifer parameter estimation). Adsorption has been investigated by means of laboratory batch tests using different tracers and involving different soils. In literature some application of tracers both to laboratory scale and to field scale can be found. Column tests have been performed also to test the effectiveness of different test equipment and to investigate the influence of some test parameters on the calculation of effective porosity and pore water velocity. These considerations and test results are very useful to advise the choice of the best tracer to be used in tracer field tests

Parameters of flow in porous alluvial aquifers evaluated by tracers

Dye tracer tests, DNA biotracer, alluvial aquifer Marche, multiwell tests

Hydraulic contacts identification in the aquifers of limestone ridges: tracer tests in the Montelago pilot area (Central Apennines)

The investigated area, located in the inner part of the Marche region (central Italy) and belonging to the carbonate Umbria- Marche ridges in the central Apennines, is characterised by very complex geo-structural setting and widespread karst phenomena that make difficult the definition of the relation among the aquifers basing only on the hydrogeological survey. Hence, the presence of different flowpaths among aquifers of the Umbria-Marche hydrostratigraphic sequence and of tectonic contacts among the different structures is verified using tracer tests. In particular, the tests showed that the Calcare Massiccio and the Maiolica aquifers are connected under certain tectonic conditions. A new tracer given by a single stranded DNA molecule and traditional fluorescent dyes have been injected into the Montelago sinkhole in different periods (during the recharge and during the discharge) and recovered in several points along the expected hydrogeological basin, using either manual and automatic sampling. Fluorescent traps were positioned in creeks, rivers and springs. The DNA molecule is useful to trace surface water and groundwater, is detectable even at very low concentrations, no significant change in water density and viscosity can be observed and its use is not dangerous for the environment. The results stress the suitability of DNA as hydrogeological tracer, capable to identify connections among aquifers and study different flowpaths even in high flow conditions when traditional tracers are more and more diluted. Moreover, fluorescein tracer allowed for the transport parameter determination, giving mean velocities ranging from 100 to 3000 m/day and mean residence time from some tens to hundreds of hours, and determining the aquifer volumes

Modelling Shallow Groundwater Evaporation Rates from a Large Tank Experiment

AbstractA large tank (1.4 m x 4.0 m x 1.3 m) filled with medium-coarse sand was employed to measure evaporation rates from shallow groundwater at controlled laboratory conditions, to determine drivers and mechanisms. To monitor the groundwater level drawdown 12 piezometers were installed in a semi regular grid and equipped with high precision water level, temperature, and electrical conductivity (EC) probes. In each piezometer, 6 micro sampling ports were installed every 10 cm to capture vertical salinity gradients. Moreover, the soil water content, temperature and EC were measured in the unsaturated zone using TDR probes placed at 5, 20 and 40 cm depth. The monitoring started in February 2020 and lasted for 4 months until the groundwater drawdown became residual. To model the groundwater heads, temperature, and salinity variations SEAWAT 4.0 was employed. The calibrated model was then used to obtain the unknown parameters, such as: maximum evaporation rates (1.5-4.4 mm/d), extinction depth (0.90 m), mineral dissolution (5.0e-9 g/d) and evaporation concentration (0.35 g/L). Despite the drawdown was uniformly distributed, the increase of groundwater salinity was rather uneven, while the temperature increase mimicked the atmospheric temperature increase. The initial groundwater salinity and the small changes in the evaporation rate controlled the evapoconcentration process in groundwater, while the effective porosity was the most sensitive parameter. This study demonstrates that shallow groundwater evaporation from sandy soils can produce homogeneous water table drawdown but appreciable differences in the distribution of groundwater salinity

Groundwater-surface water interaction revealed by meteorological trends and groundwater fluctuations on stream water level

The importance of considering groundwater (GW) and surface water (SW) as a single resource of two interconnected components has rapidly increased during the last decades. To investigate GW-SW interaction in an aquifer system exploited by several pumping wells, an integrated continuous monitoring of the hydrological conditions was carried out. The sub-catchment (14 km2), located in the Aspio basin near Ancona (Central Italy), is drained by a small stream named Betelico, and it is characterised by the presence of an unconfined alluvial aquifer and a semi-confined limestone aquifer. The aim of this study is to evaluate the drivers of stream drying up occurred during the last couple of years. This has been achieved by applying a trend analysis on rainfall, air temperatures, piezometric and stream level, and well pumping rates. Precipitation trends were analysed over a 30-years period through the calculation of the Standard Precipitation Index (SPI) and through heavy rainfall events frequency plots, while the correlation between piezometric stream levels and pumping rate was analysed during the last six years. The groundwater level was compared with the stream baseflow level, highlighting the interconnection between GW-SW over the years. The analysis on the water surplus (WS) trend, together with the rainfall events characterisation, supports the hypothesis of the decrease in recharge rate as the main driver of the stream drying up. This case study stresses the importance of studying GW-SW interactions in a continuously changing climatic context characterised by a decreasing precipitation trend, coupling both the advantages of a robust method like trend analysis on time series and the field continuous monitoring

Tecniche e metodologie per la caratterizzazione idrodinamica degli acquiferi fessurati

L’attività di ricerca che è stata sviluppata durante il dottorato ha approfondito ed affinato metodiche che hanno visto l’impiego di traccianti di comune utilizzo in idrogeologia e di nuova generazione, verificandone eventuali interazioni/assorbimento con materiali rappresentativi degli acquiferi di differenti domini idrogeologici dell’Italia centrale. In particolare l’utilizzo di un biotracciante (molecole di DNA), sperimentato in ambito scientifico internazionale fino ad ora solamente nello studio di acque superficiali, ha consentito di mettere a punto una nuova metodologia nello studio delle acque sotterranee. Tale metodica è stata sperimentata in un laboratorio appositamente realizzato per confrontare diversi traccianti e diversi materiali acquiferi, ed è stata poi applicata con successo in campagna, in una struttura idrogeologica della dorsale carbonatica umbromarchigiana. Una parte non trascurabile dell’attività di ricerca è stata infine rivolta alla ricostruzione dettagliata dei modelli idrogeologici concettuali ed alla parametrizzazione idraulica degli acquiferi carbonatici. I risultati ottenuti da prove di laboratorio in colonna e su batch test con diversi traccianti sono: le differenze dei tempi di arrivo dei picchi, a parità di condizioni idrauliche, sono dovuti alla diversa geometria delle colonne; i valori di porosità efficace sono molto vicini ai valori effettivamente ricavati indirettamente; i valori di velocità effettiva ottenuti con prove di tracciamento sono simili a quelli ottenuti per via indiretta. La sperimentazione con il biotracciante DNA nei test di colonna e di campagna ha mostrato la sua efficacia in acquiferi carsici caratterizzati da condotti o doppia porosità, ma meno in acquiferi porosi se l’obiettivo è la determinazione della porosità efficace; un flusso quasi esclusivamente convettivo nei test su colonna; l'adsorbimento del DNA sulla roccia calcarea è trascurabile, così il biotracer si comporta come un tracciante conservativo rispetto a materiali carbonatici

Best tracer selection for hydrogeological investigations: preliminary results from laboratory test

Tracers techniques are a good tool to investigate groundwater dynamics; they are essential to perform measurement of hydrogeological parameters of aquifers. This study was aimed at characterizing adsorption, effective porosity and pore water velocity in soil samples collected in a hydrographic basin of Marche Region (Italy). This basin has the typical geologic and hydrogeological features of many basins in Central Italy. Therefore. the principal aim is to evaluate the best tracer to be used for hydrogeological purpose (i.e. groundwater tracer test and aquifer parameter estimation). Adsorption has been investigated by means of laboratory batch tests using different tracers and involving different soils. In literature some application of tracers both to laboratory scale and to field scale can be found. Column tests have been performed also to test the effectiveness of different test equipment and to investigate the influence of some test parameters on the calculation of effective porosity and pore water velocity. These considerations and test results are very useful to advise the choice of the best tracer to be used in tracer field tests

Best tracer selection for hydrogeological investigations: preliminary results from laboratory test

Tracers techniques are a good tool to investigate ground-water dynamics; they are essential to perform measurement of hydro-geological parameters of aquifers. This study was aimed at charac-terizing adsorption, effective porosity and pore water velocity in soil samples collected in a hydrographic basin of Marche Region (Italy). This basin has the typical geologic and hydrogeological features of many basins in Central Italy. Therefore. the principal aim is to evaluate the best tracer to be used for hydrogeological purpose (i.e. groundwater tracer test and aquifer parameter estimation). Adsorp-tion has been investigated by means of laboratory batch tests using different tracers and involving different soils. In literature some ap-plication of tracers both to laboratory scale and to field scale can be found. Column tests have been performed also to test the effectiveness of different test equipment and to investigate the influence of some test parameters on the calculation of effective porosity and pore water velocity. These considerations and test results are very useful to advise the choice of the best tracer to be used in tracer field tests