Marios C Kirlas

In this paper, we examine the accuracy of estimating the hydrogeological parameters, transmissivity (T) and storativity (S), in a confined aquifer, when there are not enough available data for pumping flow rate values. While the most popular methods, used to estimate aquifer characteristics, assume that the pumping flow rate is constant during pumping, this is practically infeasible. Violation of this assumption results in errors, which are examined in this paper using field drawdown measurements. To find the aquifer characteristics, we use two methods, testing various pumping flow rates. Firstly, we employ the Cooper -Jacob equations to calculate (T) and (S) values. Afterwards, we use these values to create hypothetical drawdowns using Theis equation and finally we estimate the Root Mean Square Error (RMSE) between the actual and the hypothetical drawdowns. Then, we repeat the same process, replacing the Cooper -Jacob equations with Genetic Algorithms and Theis equation to find the...

Groundwater vulnerability assessment is of pivotal importance for the sustainable management of groundwater resources, particularly in regions with intense agricultural activity. This research primarily aims to assess and delineate groundwater vulnerability zones using a comparative approach of three different GIS-based modified models, namely Pesticide DRASTIC-LU, Nitrate SINTACS-LU and Nitrate NV index. For this reason, eight hydrogeological parameters were employed to analyze the spatial distribution of groundwater vulnerability in the Nea Moudania aquifer, Chalkidiki, Greece. This multi-model methodology was implemented to ascertain the most reliable method for the study area. Results indicated that the southern and southwestern parts of the study area exhibited the highest vulnerability potential, whilst the northern part displayed the lowest. Moreover, single-parameter sensitivity analysis has revealed that land use and topography were the most critical parameters of the vulne...

This study aims to evaluate and identify the groundwater vulnerability zones to pollution using a Modified DRASTIC (DRASTIC-LU) model in the porous aquifer of Nea Moudania, Chalkidiki, Greece. The validation of the produced vulnerability map is made by correlating nitrate concentration data in groundwater and vulnerability index.

In this paper, the hydrogeological parameters of a confined aquifer, such as transmissivity (T),
storativity (S) and radius of influence (R), have been assessed using real groundwater level measurements
recorded by a monitoring network, consisting of automated municipal water supply boreholes at Nea
Moudania aquifer, Chalkidiki, Greece. Particularly, the paper focused on the correlation between the
drawdown and the constant flow rate during pumping time. So the Cooper-Jacob and the recovery test
method were applied in order to delineate if turbulent head losses occur, as well as the impact of incorrect
measurements of the radial distance (r) in the accuracy of estimating S values. The results show that a) the
occurrence of a linear correlation between s and Q indicates a negligible turbulent head loss in the pumping
wells and thus a reasonable flow rate usage, b) the validity of storativity values could be compromised if the
r value is not accurately measured, and c) recovery test method can be used as an indicator of residual
drawdown (s’) caused by previous pumping cycles, when the straight line intersecting the logarithmic t/t’
axis has a value greater than 1.

The study area is the hydrological basin of Agioi Anargiroi (Korisos basin), which is extended at the Kastoria Prefecture (West Makedonia), eastern of the city and the lake of Kastoria. The area of the study basin is 89.25 Km2, of which 24.6 Κm2 belong to lowlands and 64.65 Km2 belong to mountainous areas. A regular distribution of the different elevations is observed in the study area. Moreover, the altitude varies from 651 m to 1680 m (Kronos Mountain) and it has a mean altitude of approximately 984 m above sea level and a mean slope around 28.6%. Xiropotamos torrent drains the basin and it is classified as fifth class (Horton’s classification, 1945). The hydrographic network in mountainous area is highly developed too. The geological formations of the study basin belong to Pelagonian geotectonic zone. Ιn the lowlands τhe basin of Korisos is covered by quaternary deposits (27.6% of the area) and in the mountainous area is covered by crystalline and metamorphic rocks (72.4% of the area). More specifically the lowlands are covered by recent deposits, whereas in the mountainous and semi-mountainous areas occur schists and phyllites at the southeastern part, granite-gneiss at the northern part of the basin and gneisses and amphibolites, which cover the largest part of the basin. In addition, seven deformational events (DHP and D1 to D6) occur in the broader area during the Alpine orogeny. The mean annual precipitation in the area of study amounts to 663 mm (period 2004- 2007) and increases by 40.4 mm per 100 m of ground elevation. The total rainfall is 61x106 m3 and the total runoff is equal to 16.73x106 m3. A productive unconfined aquifer is developed in the alluvial deposits, which consists of successive water bearing layers. The thickness of the alluvial deposits, based on borehole lithological profiles, ranges from 30 m in the eastern part to 140 m in the central part of the basin and increases from the northern part to the southern part of the study area. The groundwater recharge in the alluvial unconfined aquifer occurs via the following mechanisms: the most important mechanism is via direct infiltration of rainfall, then via infiltration through torrent beds and finally via return flow of irrigated water. Groundwater flow is from north-eastward to south-westward toward the Kastoria Lake. Moreover, as it was measured from the compiled piezometric maps, the mean hydraulic gradient (i) was 1.5x10-3. In Korisos basin the average hydraulic conductivity value (k) was 6.7×10–5 m/s, the transmissivity value (T) varied between 1.4×10-3 and 1.0×10-2 m2/s and the storage coefficient value (S) varied between 1.9×10-4 and 9.3×10-3. All the hydraulic parameters were deduced from the conducted pumping test analyses applying Jacob and Theis methods. Generally, the groundwater quality is suitable for irrigation use and domestic supplies. The predominant water type of groundwater in the study area is Ca-HCO3. Due to intensive agricultural activities, high nitrate concentrations were recorded locally. Furthermore, it was generally observed an increase of the electrical conductivity of the groundwater from the recharge area to the downwards (Lake of Kastoria). The mathematical code MODFLOW with the use of GMS 7.1 software (free edition from Aquaveo) was applied in the Quarternary deposits of the area for steady state conditions. The piezometric surface of the period May 2004 was used to describe the initial heads in MODFLOW code. Model calibration carried out successfully as the deviations between the computed and the observed head values were insignificant and also as the Root Mean Square Error (RMSE) had a value of about 0.61 m (calibration target within ±1 m).