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Seawater intrusion in the gravelly confined aquifer of the coastal Pisan Plain (Tuscany): hydrogeological and geochemical investigation to assess causes and consequences
No full textThe gravelly horizon of the Pisa plain multilayered system is a confined aquifer tapped by a large number of wells. It hosts a very important water resource for drinking, industrial and irrigable uses, but may be affected by seawater intrusion coming from the coastal area; most wells is distributed inland, anyway a significant exploitation along the coastal area is also present to supply farms and tourist services. Previous hydrogeological and geochemical investigations carried out in coastal area stated maximum percentage of seawater in gravelly aquifer of about 7-9% and suggested the presence of two different mechanisms (Doveri et alii, 2010): i) a direct seawater intrusion from the zone where the gravelly aquifer is in contact with the sea floor; ii) a mixing process between freshwater and seawater, the latter deriving from the Arno river-shallow sandy aquifer system. Basing on these results, since January 2012 a new two-year project was financed by the MSRM Regional Park. Major aims are a better definition of such phenomena and their distribution on the territory, and an assessing of the seawater intrusion trend in relation to groundwater exploitation. Eleven piezometers were realised during first semester of 2012, thus improving the measurement network, which is now made up by 40 wells/piezometers distributed on about 60 km^2. Comparing new and previous borehole data a general confinement of the gravelly aquifer is confirmed, excepting in the northern part where the aquifer is in contact with the superficial sandy one. Preliminary field measurement was performed in June 2012, during which water level (WL) and electrical conductivity (EC) data were collected. WLs below the sea-level were observed on most of the studied area, with a minimum value of about -5 m a.s.l. in the inner part of the northern zone, where major exploitation is present. Moreover, a relative minimum of WL (about -2 m a.s.l.) is present near the shoreline in the southern zone. In the latter EC is diffusely high from shoreline up to 5 km apart and reaches a maximum value of about 7,000 μS/cm. Toward North a general EC decreasing is observed and values below 2,000 μS/cm are measured in most of water-wells. On a limited area close to the Arno River, values higher than 3,000 μS/cm are nevertheless present. Hydraulic conductivity values between E-03 and E-05 m/s were achieved by means of some slug and pumping tests performed on new piezometers. During this month other hydraulic tests will be performed, and monitoring of EC, T and WL will be started using automatic probes; at the same time, the pumping rates of major farms wells will be monitored. Furthermore, a water sampling field will be carried out in the next month, and the collected samples will be analysed in chemical elements and water isotopes. Thus, a first picture of the seawater intrusion and its causes will be available. References Doveri M., Giannecchini R. & Butteri M., 2010. Seawater intrusion in the Versiliese-Pisan coastal aquifer system (North-western Tuscany): results from a hydrogeologic-hydrogeochemical study. Salt Water Intrusion Meeting, Azores 2010. Proceedings SWIM21, 150-153
The study of the seawater intrusion in the Versiliese-Pisan coastal plain (North-Western Tuscany) by means of hydrogeological, chemical and isotopic tools
No full textHydrogeologic-hydrogeochemical multidisciplinary study of the gravel confined aquifer in the coastal Pisan Plain (Tuscany) between the Arno River and Scolmatore Canal (Tuscany)
No full textThe gravelly horizon of the Pisa plain multilayered system, located at a depth between 50 and 100 m under the sea level and about 10-20 m thick, is a confined aquifer tapped by a large number of wells. It contains a very important water resource for drinking, industrial and irrigable uses, although in some cases the groundwater is of poor quality.
In order to evaluate if in the coastal area between Arno River and Scolmatore Canal this aquifer is interested by seawater intrusion and to know the mixing mechanisms with fresh water, a multidisciplinary study was carried out by means hydrostratigraphic correlations, water level collection and chemical and isotopic analysis. In particular, three on-site surveys were carried out in June and August 2008 and April 2009. In each point measured, piezometric values below the sea level were collected; particularly depressed levels were registered in August 2008 in the southern part of the study area. Water-wells sampled along the coast, less than 1.5 km far from the coastline, show chemical composition and 18O/16O ratios indicative of seawater-fresh water mixing. This phenomenon, in agreement with piezometric conditions, is more evident in the southern zone, toward the Scolmatore Canal, where the fraction of salt water, calculated using the mass balance model of Cl, Br and 18O/16O ratio, is about 7-8%. The most part of the other samples, collected up to 5 km from the coastline, was not interested by seawater; in these cases, groundwater shows the same characteristics found toward the internal part of the Pisa plain, with relatively low TDS and 18O/16O ratios indicative of recharge average altitudes higher than local altitudes. Only two samples, collected near the Arno River, showed chemical and isotopic characteristics indicative of a seawater presence. In these cases 18O/16O ratios values show clearly that the seawater intrusion does not directly happen in the gravelly aquifer but trough the shallow sandy aquifer which in this zone is in contact with the grave
L’intrusione marina nella fascia versiliese-pisana. Studio multidisciplinare idrogeologico-geochimico dell’acquifero confinato in ghiaie nella fascia costiera tra il Fiume Arno ed il Canale Scolmatore. Rapporto Tecnico-Scientifico
No full textPREMESSA
Nel presente rapporto vengono descritte le attività di studio svolte ed i risultati ad oggi conseguiti, in riferimento alla convenzione stipulata il 23/01/2009 (e successiva integrazione; Det. N. 581 del 09/07/2009) dall’Ente Parco Regionale Migliarino San Rossore Massaciuccoli (di seguito Parco MSRM) con il Dipartimento di Scienze della Terra dell’Università di Pisa (di seguito DST) e che prevede la partecipazione tecnico-scientifica dell’Istituto di Geoscienze e Georisorse dell’Area della Ricerca-CNR di Pisa (di seguito IGG).
In particolare, la presente relazione riguarda l’indagine conoscitiva di cui all’Art. 3 punto b) della citata convenzione e successiva integrazione, ovvero lo studio dell’acquifero multistrato confinato della Pianura di Pisa nella fascia costiera (fig. 1), con particolare riferimento agli orizzonti acquiferi in ghiaia ed ai meccanismi che regolano il mescolamento tra la acque in essi circolanti e l’acqua di mare.
Il lavoro è stato condotto dal DST e dall’IGG per mezzo di un’integrazione delle conoscenze idrostrutturali ed un’analisi delle condizioni piezometriche e idrochimico-isotopiche nei tre periodi Giugno e Agosto 2008 e Aprile 2009.
Allo scopo di una più chiara ed esauriente illustrazione degli aspetti che condizionano la circolazione e la qualità delle acque degli acquiferi studiati, il presente elaborato tiene conto della totalità dei dati prodotti sull’intero periodo di studio; di conseguenza, vengono considerati anche i risultati già presentati con la relazione preliminare di Giugno 2008 (Indagine conoscitiva speditiva sulla situazione idrostratigrafica, piezometrica e idrochimica nella fascia di raccordo tra gli acquiferi freatici costieri e l’acquifero multistrato della pianura pisana), nonché quelli illustrati nella relazione di Gennaio 2009 (Studio idrogeologico speditivo sulle acque circolanti all’interno dell’acquifero in ghiaia nella zona di San Piero a Grado, Viale del Mare (S.P. 22), nella Tenuta di Tombolo) dal Dott. Geol. Pietro Gattai, che, in qualità di consulente del Parco MSRM, ha seguito da vicino l’intero progetto in tutte le sue fasi
Hydrogeologic-hydrogeochemical multidisciplinary study of the confined gravelly aquifer in the coastal Pisan Plain between the Arno River and Scolmatore Canal (Tuscany)
No full textThe gravelly horizon of the Pisa plain multilayered system, located at a depth between 50 and 100 m below the sea-level and about 10-20 m thick, is a confined aquifer tapped by a large number of wells. It contains a very important water resource for drinking, industrial and irrigable uses, although in some cases the groundwater is of poor quality.
In order to evaluate if in the coastal area between the Arno River and Scolmatore Canal this aquifer is interested by seawater intrusion and to understand the mixing mechanisms with fresh water, a multidisciplinary study was carried out by means of hydrostratigraphic correlations, water level collection and chemical and isotopic analysis. In particular, three on-site surveys were carried out in June and August 2008 and April 2009. In most of the measured points, piezometric values below the sea-level were collected; particularly depressed levels were registered in August 2008 near the coastline in the southern part of the study area (Calambrone zone) and in the internal part to North (S. Piero a Grado zone). Water-wells sampled along the coast, less than 1.5-2 km far from the coastline, show chemical composition and δ18 O‰ values indicative of seawater-fresh water mixing. This phenomenon, in agreement with piezometric conditions, is more evident in the southern zone, toward the Scolmatore Canal, where the fraction of salt water, calculated using the mass balance model of Cl, Br and δ18 O‰, is about 7-8%.
Most of the other samples, collected up to 5 km from the coastline, were not interested by seawater; in these cases, groundwater shows the same characteristics found toward the internal part of the Pisa plain, with relatively low TDS and δ18O‰ indicative of recharge average altitudes higher than local altitudes. Only two samples, collected in the North-East portion near the Arno River, showed chemical and isotopic characteristics indicative of a seawater presence of about 8-9%. In these cases, δ18 O‰ values clearly show that the seawater intrusion does not directly occur in the gravelly aquifer, but trough the shallow sandy aquifer, which in this zone is in contact with the gravel
Studio idrogeologico-geochimico dell’acquifero freatico nella zona compresa tra il Canale Burlamacca ed il Fosso della Bufalina (Viareggio, Toscana)
No full textThe study area is located in the coastal plain between the Burlamacca Canal and Bufalina Ditch (South of Viareggio, Northern Tuscany) and is bounded by the topographically depressed zones of the Massaciuccoli Lake to the East. Due to its peculiar physiographic, hydrogeological and anthropic features, this territory well represents a case study of the natural and human factors combination in the enhancing of the groundwater degradation caused by seawater intrusion. The hydrogeological-hydrogeochemical interdisciplinary approach of this study allowed to define the hydrostructural, piezometric and hydrochemical-isotopic characteristics of the phreatic aquifer as well as to assess the relationship between groundwater and superficial water and their seawater contamination. The hydrostratigraphic study let us to individuate a phreatic aquifer, 20-40 thick, characterized by sandy and sandy-silty deposits. A continuous clayey horizon is present beneath the last, acting as impermeable bedrock. Both in the low stage (October 2005) and in the high stage (May 2006), the piezometric surface shows two areas characterized by values under the sea level (along the coastline in the southern portion and close to the artificial lakes). As confirmed by chemical and isotopic data, such situations, linked to a over-exploitation of the water resource (mainly farms and bathing establishments), cause favorable conditions to drain seawater in aquifer. The surveys let us to assume an interpretative model of the preferential path of the seawater in the phreatic aquifer. The seawater intrusion in aquifer occurs by means both of advancing from the coastline of the seawater-fresh water interface, and of water drainage from the artificial canals system. In this case, the seawater may reach the lakes through the Burlamacca Canal
Seawater intrusion in the Versiliese-Pisan coastal aquifer system (North-western Tuscany): results from a hydrogeologic-hydrogeochemical study
No full textThe multilayered aquifer system of the Versiliese Pisan coastal plain is mainly made up of sandy and gravelly horizons. The aquifers are locally affected by intense exploiting for drinking, industrial and irrigation uses, which favours seawater intrusion. In order to study this phenomenon and understand the mixing mechanism with freshwater, a project co financed by the Migliarino S.Rossore Massaciuccoli Regional Park is being carried out since 2005. This project consists in a multidisciplinary study carried out by means of hydrostratigraphic correlations, water level measurements and physico chemical (electric conductivity, temperature, pH), chemical (principal chemical elements and Br) and isotopic analysis (18O/16O and 2H/1H ratios). In this short paper the main results regarding the zones between Burlamacca Canal and Bufalina Ditch (zone A) and between Arno River and Scolmatore Canal (zone C) are presented. In the intermediate area (zone B) the study is still in progress. In the zone A the 30 m thick unconfined sandy aquifer was studied, whereas in the zone B the confined gravelly aquifer (10 20 m thick) located at a depth between 50 and 100 m below the sea level was analyzed. In both zones, water levels below the sea level are referable to groundwater exploitation principally due to tourism companies and farms. Chemical and isotopic analysis in different periods highlighted a maximum salt water percentage variable in the intervals 15 30% and 7 9% for A and C zones, respectively. Isotopic tools, together with conservative chemical parameters, allowed understanding of the seawater freshwater mixing mechanisms and to verify the preferential path of the seawater
Hydrogeological-geochemical study of the phreatic aquifer in the left bank of the Arno River mouth (Tuscany) with refer to seawater intrusion
No full text
Natural and anthropic factors of the seawater intrusion. Hydrogeological-geochemical study of the phreatic aquifer in the area between Burlamacca and Bufalina Canals (Viareggio, Tuscany)
No full textThe study area is located in the coastal area between the Burlamacca and Bufalina Canals (south of Viareggio, northern Tuscany) and is bounded by depressed areas of the Massaciuccoli Lake to the west. Due to its peculiar physiographic, hydrogeological and anthropic features, this territory represents an exemplary case of study of the combination of natural and anthropic factors in the exalting of the deterioration of the underground water resources due to seawater intrusion
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