Geology Reference
In-Depth Information
The vertical distribution of the CFZ (Fig. 9a) shows the occurrence of
conductive fractures both within the bottom of the saprolite (unusually
preserved fissures) and within the first 20 m of the underlying fissured layer,
with higher concentrations of fissures within its first metres (the curve on
Fig. 9b shows that observations between -6 and +24 metres can be considered
as representative, the percentage of investigated wells being higher than
50%—for a given aquifer portion, ratio between the number of available
observations and the total 19 possible measurements). The low number of
observations at shallow depths suggests that the apparent decrease in fractures
density above 15 metres is an artefact due to lack of observations.
Consequently, in such a context, it can reasonably be assumed that the
fissured layer extends above the upper limit of observations, which is
consistent with field and well geological observations.
Figure 9.
Interpretation of flowmeter-measurement profiles (19 wells)
by 0.5-metre-thick aquifer portions performed in the Maheswaram
(southern India) experimental watershed. (a) Number of identified hydraulically
conductive fissures zones (CFZ). (b) Quality of observation (see definition in the
text). (c) Hydraulic conductivity of CFZ (from Dewandel et al., 2006).
