The pumping test was made in a $9\frac{5}{8}″$ diameter open-hole interval in the conglomerates between 211 and 256.4 m. A pump was installed at 90 m depth in the cased borehole interval, and a pressure probe for the continuous registration of the drawdown was taped on the water pipe 10 m above the pump. The total duration of the step test was 67 h. The automatic drawdown registration was made every 15 s (Fig. 3).

The hydrochemical analyses of the pumped water (see Fig. 4) showed a very strong domination of the Na and Cl ions. This result, together with the calculated ion-ratios of the major elements and the minor and trace element contents (Br, Sr, Li, etc.), led to the conclusion that the water in the conglomerates is clearly of marine origin, though the concentration of total dissolved solids (conductivity of $56\mathrm{mS}{\mathrm{cm}}^{-1}$) is higher than seawater. This aquifer must be well hydraulically isolated from the formations above and beneath it; a hydraulic contact with seawater in the Gulf of Corinth is very probable.

From the several solutions provided by the software Aqtesolv^® [2] used in processing the pump-test data, the Moench leakage approach [7] (Fig. 5) provided the best fit and a hydraulic conductivity of approximately $2.7\times {10}^{-5}\mathrm{m}{\mathrm{s}}^{-1}$ for the conglomerates. The Moench leakage approach is based on the Hantush theory of leaky confined aquifers and assumes storage in the aquitards and wellbore skin. It assumes too that an aquitard is overlain by either a constant head boundary (case 1) or a no-flow boundary (case 2) [2,10]. The described first test is corresponding to ‘case 1’ because no water-level changes registered in borehole Γ₁ during pumping. The tested aquifer is confined and almost artesian (water level only 1 m below annular blow-up preventer). The total residual drawdown of more than 4.5 m (see Fig. 3) could be explained by a semi-isolated lens-shaped conglomeratic aquifer. The semi-isolation is probably due to the presence of an impervious vertical boundary to the south and to the clay layers above and beneath the tested conglomerates. It is likely that such a boundary is due to the Aigion Fault, if the fault acts in this sector as an impermeable barrier. Due to the distant hydraulic contact to the sea, a very slow recovery can be assumed. However, the best curve fitting was obtained by considering leakage through the thin, overlaying clay at 160 m depth or from deeper layers within the conglomerates.

After cementing the casing down to 708 m and coring from 708 to 744.8 m, the second pumping test was performed in the $6\frac{3}{4}″$ open hole in the Olonos–Pindos limestone (Fig. 2, 4th aquifer). The same equipment was used as in the first pumping test. The natural water pressure was 0.5 MPa and the artesian flow rate $1.9\times {10}^{-4}{\mathrm{m}}^3{\mathrm{s}}^{-1}$. Because of the very poor permeability of the limestones, it was necessary to reduce the pumping rate through curbing (closing the valve to increase pressure). After several trials, it was finally possible to perform the test at a flow rate of $3.9\times {10}^{-4}{\mathrm{m}}^3{\mathrm{s}}^{-1}$ (Fig. 6). The hydrochemical analyses (Fig. 7) of the pumped water show a total mineralisation <1 $\mathrm{g}{\mathrm{l}}^{-1}$ (drinking-water quality), a strong domination of Na ions (similar to the first test in the conglomerates), but a relatively high HCO₃⁻ concentration (different compared to the first test). This result, together with the calculated ion ratios and the artesian pressure of 0.5 MPa, led to the conclusion that the water in the limestones was recharged in the hinterland of Aigion to the south, where the limestones are outcropping. Very likely reactions with clay minerals (cation exchange) occur to justify the Na enrichment and the observed Ca and Mg removal from solution.

The tested aquifer is hydraulically well isolated from the aquifers above by aquicludes. Any hydraulic contact with seawater can be discarded. The physical water parameters measured during the test at the surface in a bucket (electric conductivity$=780\mu \mathrm{S}{\mathrm{cm}}^{-1}$ and temperature=23.5 °C) support this theory.

Using Aqtesolv^®, the best results of curve fitting (Fig. 8) are obtained by the Moench leakage approach [7] and especially by the Moench approach for fractured aquifers [6]. Data processing resulted in a transmissivity between $1.47\times {10}^{-4}{\mathrm{m}}^2{\mathrm{s}}^{-1}$ (equivalent hydraulic conductivity $4\times {10}^{-6}\mathrm{m}{\mathrm{s}}^{-1}$) for the leakage approach and $3.68\times {10}^{-6}{\mathrm{m}}^2{\mathrm{s}}^{-1}$ (equivalent hydraulic conductivity $1\times {10}^{-7}\mathrm{m}{\mathrm{s}}^{-1}$) for the fractured aquifer approach.

The following conclusion is drawn: the limestones act primarily as an artesian, confined and fractured aquifer.

After crossing the Aigion Fault by drilling, a sudden increase of pressure and water flux was observed. This observation calls for conditions typical for karstic or densely fractured units, which is supported by the analysis of the drill core obtained at 773–786 m. A three-day production test, under the coordination of F. Cornet (IPGP), covered the depth interval from 708 to 1001 m. The water temperature measured at the surface during the production test varied between 29–31 °C (average 30 °C). The artesian pressure before and after the test was constantly 1 MPa. The head losses during the artesian flow reached 0.12 MPa and were calculated according to the Darcy–Weisbach equation [1,12]. Data processing could not be done according to the theory for artesian production tests [4] because during the three days of artesian flow both drawdown (1–0.12 MPa=0.88 MPa=88 m water column) and natural flow rate ($1.5\times {10}^{-2}{\mathrm{m}}^3{\mathrm{s}}^{-1}$) remained practically constant. Therefore, the processing occurred based on the equation of Dupuit–Thiem [3,5,13] assuming a constant drawdown at the well radius, equal to 0.88 MPa of artesian pressure and a zero drawdown at a radius of influence R. Considering for this radius R possible values between 250 and 10⁴ m, an average transmissivity of 2.1–$3.1\times {10}^{-4}{\mathrm{m}}^2{\mathrm{s}}^{-1}$ resulted for the 231 m producing interval (770–1001 m in depth). These values would correspond with an average hydraulic conductivity of 0.9–$1.1\times {10}^{-6}\mathrm{m}{\mathrm{s}}^{-1}$. The analysis of the water chemistry (Figs. 9 and 10) shows that the bulk mineralisation is about 1.03 g/l, so that the water practically is of drinking-water quality except for the Na concentration. Similar to the second pumping test, we assume that the high Na concentration originates mainly from cation exchange processes within clay minerals.

The difference in water pressure (pressure step of 0.5 MPa) and in the hydraulic properties of the limestones in the hanging wall and in the foot wall of the Aigion Fault provides evidence that two compartments (aquifers?) exist that communicate hydraulically through a less permeable zone (the Aigion Fault zone plus radiolarites in the footwall).