Hydrogeologic Syntheses and Budgets - Hydrogeology: Objectives, Methods, Applications - page 162

C HAPTER B4
Hydrogeologic Syntheses
and Budgets
The fi nal report produced for a study often relies heavily on structural
and hydrogeologic maps detailing the general conditions in the study
area, on interpreted cross-sections or block diagrams illustrating the limits
of aquifers, and on schematic fi gures outlining the exchanges betwen
reservoirs (see chap. B 2-5).
When the natural conditions are complex, it may also be necessary to
illustrate certain situations with simplifi ed fi gures, intended to make the
presentation of problems that directly interest the reader more accessible.
1 DRAINAGE OF THE JURASSIC KARST UNITS
ON THE EASTERN SIDE OF THE SUBALPINE
CASTELLANE ARC , IN THE ALPES-MARITIMES
The drainage is principally through the Loup and Cagne valleys, whose
deep gorges cut into the water-bearing units all the way down to its
impermeable Triassic base. Other outlets, of lesser magnitude, line the
aquifer's southern edge, at the contact with the underlying impermeable
Triassic and Miocene units.
Figure 90 illustrates, in a simplifi ed manner, the most probable extent
of the catchment basins for the principal aquifers, based on the multiple
arguments which guided the study as it progressed, notably:
￿ the impermeable limits of the reservoir, made up of basal Triassic
units (at the bottom of the gorges, in anticlinal upwarps, and on
the southwestern front), frontal Miocene units (inserted beneath
the southeastern front's overthrust), and capping Cretaceous units
(preserved in the centers of synclines to the northwest);
￿ the rough outlines of the structure of the aquifer formation, including the
frontal overthrust, the main anticlinal axes, and the collecting faults;