All data let us to obtain the following results:

Abstract

The study area is located between the Volterra basin to the east, and the Fine River valley to the west. It includes the S. Luce - Castellina Marittima morphological ridge, characterized by medium altitude and extending with pronounced sense of lengthening N - S in the municipal territories of Chianni, Santa Luce, Castellina Marittima and Riparbella (PI).

The purpose of this Thesis is to characterize the most significant aquifers/aquitards identified by the geological reconstruction of the study area and its hydrogeological interpretation. For this characterization a study of eight sources was also carried out. The springs were observed from May 2015 to April 2016, measuring flow discharge, temperature, pH and electrical conductivity every twenty days, with two samplings performed in different seasons, for the subsequent chemical analysis of the spring water.

All data let us to obtain the following results:

- the origin of the northern sector springs is compatible with a permeability limit while in the south, where the tectonic acted more significantly resulting in more complex structures (anticlines, synclines, thrusts etc.), springs were characterized as permeability threshold;

- according to Meinzer's classification (1927), modified by Civita (2005), the springs fall within the classes 5 and 6, with minimal flow rates ranging between 0.0002 and 0.0013 m

/s and constant index of variability;

- the study of the discharge hydrographs reveals short response times for aquifers included in Flysch and Calpionelle limestones (within 1-2 days) and response times longer for acquitards in ophiolite (5-10 days);

- the depletion curves of all the springs from May 2015 to April 2016 show in general they low values of the depletion coefficient (approximately 10

days

), which indicate a slow emptying of the aquifers/acquitard systems. The higher depletion coefficient values are attributable to the springs within the more permeable carbonatic aquifer, and for springs draining portions of very fractured rocks (ex. Madonna della Salute);

- the physical parameters of groundwater (temperature and electrical conductivity) confirm a characteristic trend of hydraulic systems in which the homogenization effect prevails; the values of temperature and electrical conductivity are greater in the dry period, and decrease with the arrival of rains due to dilution effecst; in general, however, the variations of these parameters are little.

Finally, the waters are classified according to Mouren (after Shoeller, 1962) as cold water, and according to Civita (2005) as oligomineral except those of Massone spring, which are mineral;

- plotting the data obtained by chemical analysis on Piper-Hill diagram and Schoeller – Berkaloff

diagram, the groundwater result bicarbonate-alkaline with poor mineralization, except those of

Massone spring. The concentration of the main chemical elements of the springs respect the Italian

Regulation D.lgs 31/2001 for drinkable water with the exception of the Massone spring for Ni,

which needs a water treatment.