Seawater intrusion monitoring is essential to assess groundwater deterioration, guarantee sustainable use, and suggest managerial activities in coastal aquifers. The gravelly horizon of the Pisa plain multilayered system is a mainly confined aquifer hosting a very important water resource for drinking, industrial and irrigation uses. Previous hydrogeological-geochemical studies carried out in the coastal area stated both a direct seawater intrusion and a mixing process between freshwater and seawater, the latter deriving from the Arno river-shallow sandy aquifer system. Since January 2012 a new project was financed by the MSRM Regional Park. Major aims are a better definition of such phenomena and their distribution, and the assessing of the seawater intrusion in relation to groundwater exploitation. The monitoring activities consist of many surveys for the measurement of water-head and physical-chemical parameters, collecting of sample for chemical and water stable isotopic analyses, and the setting up of a network of multi-parameter probes for a continuous monitoring. The monitoring network for hydrogeological and geochemical data consists of 40 wells/piezometers on 60 km2. Eight piezometric and sampling surveys were performed for groundwater and surface water. Data on major elements and water isotopes are available for five surveys (253 samples). Vertical logs of EC and T were performed. The continuous monitoring network is formed of 13 multi-parameter probes, which hourly record water level, EC and T since August 2012. Some of these probes are located in the sandy unconfined aquifer, in order to verify possible water connections with the confined one. All data were then compared with the meteorological data, hydrometric measurements of Arno River, and the effective amount of exploitation carried out by the main users of groundwater. In relation to the gravelly confined aquifer, the results highlight a piezometric level below the sea level in most of the area during the monitoring period (jul 2012-jun 2013); high EC values, ranging from 5,000 to 7,000 μS/cm were measured in the southern portion. On the whole, the study revealed seawater intrusion in particular in the unconfined aquifer (from 50% to 90% of seawater in the area where it was studied), but also the confined aquifer begins to suffer this phenomenon (max value of 10% of seawater). Hydraulic connections between unconfined and confined aquifers are present in the northern part of the study area, probably attributable to incorrect settings of local wells.

Monitoring network of seawater intrusion in the gravelly confined aquifer of the coastal Pisan Plain (North Tuscany, Italy)

GIANNECCHINI, ROBERTO;Doveri, M.;
2015-01-01

Abstract

Seawater intrusion monitoring is essential to assess groundwater deterioration, guarantee sustainable use, and suggest managerial activities in coastal aquifers. The gravelly horizon of the Pisa plain multilayered system is a mainly confined aquifer hosting a very important water resource for drinking, industrial and irrigation uses. Previous hydrogeological-geochemical studies carried out in the coastal area stated both a direct seawater intrusion and a mixing process between freshwater and seawater, the latter deriving from the Arno river-shallow sandy aquifer system. Since January 2012 a new project was financed by the MSRM Regional Park. Major aims are a better definition of such phenomena and their distribution, and the assessing of the seawater intrusion in relation to groundwater exploitation. The monitoring activities consist of many surveys for the measurement of water-head and physical-chemical parameters, collecting of sample for chemical and water stable isotopic analyses, and the setting up of a network of multi-parameter probes for a continuous monitoring. The monitoring network for hydrogeological and geochemical data consists of 40 wells/piezometers on 60 km2. Eight piezometric and sampling surveys were performed for groundwater and surface water. Data on major elements and water isotopes are available for five surveys (253 samples). Vertical logs of EC and T were performed. The continuous monitoring network is formed of 13 multi-parameter probes, which hourly record water level, EC and T since August 2012. Some of these probes are located in the sandy unconfined aquifer, in order to verify possible water connections with the confined one. All data were then compared with the meteorological data, hydrometric measurements of Arno River, and the effective amount of exploitation carried out by the main users of groundwater. In relation to the gravelly confined aquifer, the results highlight a piezometric level below the sea level in most of the area during the monitoring period (jul 2012-jun 2013); high EC values, ranging from 5,000 to 7,000 μS/cm were measured in the southern portion. On the whole, the study revealed seawater intrusion in particular in the unconfined aquifer (from 50% to 90% of seawater in the area where it was studied), but also the confined aquifer begins to suffer this phenomenon (max value of 10% of seawater). Hydraulic connections between unconfined and confined aquifers are present in the northern part of the study area, probably attributable to incorrect settings of local wells.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/835014
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