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Società Geologica Italiana, Calligaris, Chiara, Zini, Luca, Treu, Francesco, Daniela, Iervolino, Federica, Lippi, Cucchi, Franco |
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One of the objectives of the European Directive 2000/60 and the Legislative Decree 152/06 is the sustainability of water-balance in a reference area with the aim of protecting water resources. Thorough verification of the water-balance it will be possible to obtain the consumption sustainable water value and, together with other protective measures planned, the achievement of environmental quality. The constantly increasing water demand for human consumptions and the constant use of water resources induced to study deeply the Friuli Venezia Giulia Plain (north eastern part of Italy) where all the water resources of the Region are storeged. The aim of the present research is to realize a water-balance in order to understand the amount of the water resource and its use. To reach this aim, the Geosciences Department from Trieste University has been engaged by the Hydraulic Survey of the Friuli Venezia Giulia Region in order to coordinate an integrated study finalized to the Friuli Venezia Giulia Plain confined and unconfined aquifer geometries reconstruction and to provide guide-lines for water rational exploitation (Agreement D.G.R. n. 1827 dd. 27.07.2007). Water-balance means the comparison between the water resources, available or obtainable, and the withdrawn in the reference area. In order to define water consumption, 2 Data Base: one for the domestic use (47709 estimated water-wells), and the other one for all the other uses (7930 water-wells) have been analyzed. Domestic, potable, agricultural, industrial, hygienic and sanitary, fish breeding and geothermal uses have been considered. For every single use have been calculated the number of withdrawal points and the amount of withdrawal for every single aquifer. Figure 1 is showing the actual situation. CALLIGARIS C. (*)., ZINI L.(*), TREU F.(*), IERVOLINO D.(**), LIPPI F.(**), CUCCHI F.(*) Precipitation, evapotraspiration, runoff, infiltration and river discharge were used to obtain input and output water values from the regional system. As result, the water availability for the Low Plain is abundant (197,7 m3/s), depending from the High Plain recharge and from the water insisting on the mountain basin, but also the total water extractions are consistent (59,3 m3/s). In fact, the total withdrawal value evaluated by the census of 55639 sampling points present in the Friuli Venezia Giulia is 59,3 m3/s, of which only 10,2 m3/s are relative to groundwater phreatic withdrawals of the Low Plain. 49,1 m3/s is therefore the amount of the groundwater withdrawals from the phreatic High Plain and the artesian aquifers. To this value must be added the withdrawal contribution from the Veneto Region (in Tagliamento right side). The withdrawals intensity is well explained in the Figure 1 where they are expressed in l/s for km2 for every single water body. The total amount of withdrawals for single aquifer is represented in Figure 2. While from a comprehensive analysis the current use of the water resource seems to be sustainable, a specific analysis made on the single water body shows great, critical and substantial unevenness. In particular, it highlights the overfishing of the area located in the Tagliamento right side where consumers are heavily unbalanced in relation to charging. The hydroelectric and irrigation withdrawals on the mountain rivers create a significant deficit in the recharge of the High Plain in the Tagliamento right side. The result is the crisis on the artesian groundwater in the Low Plain on the right side of Tagliamento River. This imbalance is offset by increasing recall of phreatic and artesian groundwater from the left side of Tagliamento. The withdrawals that interest, with different intensity, all the artesian aquifers, induce an always greater mixing in the waters with the consequent substitution of the deep ones with the phreatic. Water age analyses indicate that the waters deeper than 110 m from the ground level (aquifer C), are older than 15000 years (CUCCHI et alii, 2008). This is a resource of really high quality but with a low natural recharge. The force exerted by the wild withdrawals, cause a depletion of water and take to their accelerate substitution by younger waters having match lower quality. The balance is not sustainable any more, water table is subsiding 0,1-0,4 m/yr (CUCCHI et alii, 1999), the pressure of the confined aquifers is dropping and this imply a different policy geared towards a conscious use of the resource. REFERENCES CUCCHI F., FRANCESCHINI G., ZINI L., (2008) - Hydrogeochemical investigations and groundwater provinces of the Friuli Venezia Giulia Plain aquifers, northeastern Italy. Environ. Geol., 55, 985-999. CUCCHI F., MASSARI G., OBERTI S. (1999) - Water table fluctuations in the northern Friuli Plain. Gortania, 21, 41-51. |
