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| Titel |
Using isotopic and hydrochemical data to investigate groundwater recharge
and discharge in a highly impacted watershed: the Oglio River, northern
Italy |
| VerfasserIn |
Marco Rotiroti, Tullia Bonomi, Letizia Fumagalli, Sara Taviani, Gennaro A. Stefania, Chiara Zanotti, Martina Patelli, Valentina Soler, Elisa Sacchi, Barbara Leoni |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144379
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| Publikation (Nr.) |
 EGU/EGU2017-8195.pdf |
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| Zusammenfassung |
| The investigation of groundwater recharge and discharge areas is crucial to define
groundwater flowpaths and assess groundwater vulnerability to pollution. To this purpose,
stable isotopes of the water molecule and hydrochemistry were used to investigate an area
located in the Po Plain (N Italy) that is highly impacted by human activities, in particular, by
agriculture.
The study area covers ∼1900 km2 of the Oglio River basin, between the outflow from
Lake Iseo and the confluence into Mella River. This area hosts a sandy mono-layer aquifer in
its northern part (higher plain), that passes southwards into a multi-layer aquifer (lower
plain) with increasing silt and clay contents. The transition between higher and
lower plain is marked by a series of springs, the so called “spring belt". The area is
crossed by hundreds of irrigation channels, fed by Oglio River water in its upstream
stretch.
During 4 field surveys (November 2015, February, June and September 2016),
groundwater, Oglio River and its main tributaries, Lake Iseo and springs were sampled. In
each survey, up to 58 groundwater, 20 river water, 1 lake water and 7 spring water samples
were collected. Rainwater was continuously collected between November 2015 and 2016 at 2
locations. All water samples were analysed for major ions, trace elements (Mn, Fe and As)
and δ18O/δ2H in water.
Hydrochemical data showed that the higher plain is characterized by an oxidized
hydrofacies with higher concentrations of NO3 whereas the lower plain shows a reduced
hydrofacies with higher concentrations of Mn, Fe, As and NH4. This is mostly related to the
aquifer permeability and suggests conditions open to surface recharge in the former.
Indeed, water isotopes revealed that the aquifer in the higher plain is recharged
by surface water (irrigation channels and Oglio River in its upstream stretch) and
local precipitation, and discharges into springs, the Oglio River and through well
abstractions; Lake Iseo does not directly recharge the aquifer. The strong impact of
recharge by irrigation water is clearly observed during summer. The multi-layer
aquifer in the lower plain is recharged by the upstream flow from the higher plain
aquifer, and discharges into the Oglio River and its tributaries, and through well
abstractions. In the lower plain, recharge by leaking irrigation channels is only seen for
shallow aquifers, whereas deep aquifers are no or slowly recharged by irrigation
water.
The present work confirms the use of stable isotope and hydrochemical data as powerful
tools for identifying groundwater recharge and discharge. These results could be used for a
future assessment of groundwater vulnerability to human pollution in the study
area.
This work was supported by Fondazione Cariplo, grant 2014-1282. |
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