Page 8 - Grillini2015

FIGURE 8 The Chebotarev diagram: water classification and
evolution of the groundwater chemical composition
FIGURE 9 The Schoeller diagram: comparison between the
ionic concentrations from the groundwater samples
collected in Favignana
hydrochemical characters. A detailed analysis of the
Schoeller diagram created for these water samples confirms
a similar composition for most of the examined waters.
Particularly, most of the segments forming the Research & development
distinctive lines of the water samples taken from wells
FA04, FA13, FA15, and FA26 show a quasi-parallel
trend, not only reciprocally, but also compared with the
standard seawater line used as a comparison (sea water
with a salinity of 35‰) [45]. These samples, showing
electrical conductivity values exceeding 7000 µS/cm,
represent the end-members of a geochemical facies
evolved into chloride-alkaline through the mixing of
originally fresh water with other saltier water due to a
probable marine intrusion.
Discussion
Both in the western and in the eastern sectors, the water
table is always few tens of centimeters above sea level,
in wells where the mouth is as high as 32 meters as well
as in wells where it is just a couple of meters above sea
level (Figure 10). This result is evidence of the poor
groundwater resource all over the island, independently
from the nature or characteristics of the terrain, where
the well has been drilled or excavated.
Between the wet and dry season the water table shows
no significant differences, since they are limited to a few
centimeters. Oh the other hand, the Favignana’s people
is accustomed since the first prehistoric colonization to
cope with drought and poor water resource: they have
FIGURE 10 Water levels vs. ground elevations
25EAI Energia, Ambiente e Innovazione 4/2015