Abstract:Studies on the hydrogeological conditions of the Mesogea basin in east Attica reveal that the aquifers developed on the post-alpine formations at the inner part of the coastal brackish zone exhibit positive hydraulic head. These Neogene and Quaternary deposits present high salt concentrations. Selected points were sampled (total 85: 51 wells and 34 boreholes) in order to obtain hydrogeological and hydrochemical data for a better understanding of the structure, operation and dynamics of the aquifer of the area. Statistical methods, R-mode factor analysis and scatter-plot diagrams were used for the hydrochemical analysis and presentation of the data. The groundwater resources are relatively weak and there is significant quality degradation due to the geological structure of the greater area, as well as the bad management of the aquifer and anthropogenic activities. Groundwater is characterized by high salt concentrations. Electrical conductivity values range between 260 and 6970 µS cm 1 . High salt concentrations at the coastal aquifers are due to sea intrusion, whereas they are attributed to the dissolution of minerals of the geological environment in the inland area. The groundwaters of the study area can be classified into five water types: Ca-HCO 3 , Mg-HCO 3 , Na-HCO 3 , Na-Cl and Mg-Cl. They are saturated in dolomite and calcite, whereas they are unsaturated in anhydrite. High ion concentrations, e.g. NO 3 (0-221 mg l 1 ), NH C 4 (0Ð01-1Ð88 mg l 1 ), PO 3 4 (0Ð01-6Ð75 mg l 1 ), as well as high heavy metals concentrations are attributed to anthropogenic impacts.
The degradation of groundwater quality, which has been noted in the recent years, is closely connected to the intensification of agriculture, the unreasonable use of chemical fertilizers and the excess consumption of large volumes of irrigation water. In the hilly region of central Thessaly in Greece, which suffers the consequences of intense agricultural use, a hydrogeological study is carried out, taking groundwater samples from springs and boreholes in the Neogene aquifers. The aim of this study is the investigation of irrigation management, water quality and suitability for various uses (water supply, irrigation), the degradation degree and the spatial distribution of pollutants using GIS. The following hydrochemical types prevail in the groundwater of the study area: Ca-Mg-HCO 3 , Mg-CaNa-HCO 3 and Na-HCO 3 . In the above shallow aquifers, especially high values of NO 3 -(31.7-299.0), NH 4 ? (0.12-1.11), NO 2 -(0.018-0.109), PO 4 3-(0.07-0.55), SO 4 2-(47.5-146.5) and Cl -(24.8-146.5) are found, particularly near inhabited areas (values are in mg L -1 ). The water of shallow aquifers is considered unsuitable for human use due to their high polluting load, while the water of the deeper aquifers is suitable for human consumption.Regarding water suitability for irrigation, the evaluation of SAR (0.153-7.397) and EC (481-1,680 lS cm -1 ) resulted in classification category 'C3S1', indicating high salinity and low sodium water which can be used for irrigation in most soils and crops with little to medium danger of development of exchangeable sodium and salinity. The statistical data analysis, the factor analysis and the GIS application have brought out the vulnerable-problematic zones in chemical compounds of nitrogen and phosphates. The groundwater quality degradation is localized and related exclusively to human activities. Based on 2005 and 2008 estimates, the annual safe yield of the region's aquifers were nearly 41.95 MCM. However, the existing situation is that 6.37 MCM of water is over extracted from these aquifers.
Groundwater samples were collected from 25 sampling sites of the Oropos-Kalamos basin aiming to describe the groundwater quality in relation to geology, lithology and anthropogenic activities of the study area. Chromium speciation analysis, factor analysis, GIS database and geochemical data proved successful tools for the identification of natural and anthropogenic factors controlling the geochemical data variability and for the identification of the redox couple controlling Cr speciation. A Durov diagram is used to classify groundwater quality into five types: Ca-HCO 3 , Mg-HCO 3 , Na-Cl, Mg-Cl and Ca-Cl. The groundwater quality of Oropos-Kalamos is influenced by various natural and anthropogenic factors. Evaluation of water quality for drinking and irrigation purposes is discussed.
Abstract:In this paper the groundwater quality of the southern part of Korinthos region (north-east Peloponnese) is discussed. The geology is characterized by a thick sequence of Neogene marls alternating with sandstones, overlain by superficial Quaternary deposits. The latter consist of a mixture of loose materials such as conglomerates, marly sandstones, sands and clay to silty sands. The area is crossed by a fault system parallel to the coastline, and the Quaternary sediments have formed extended Tyrrhenian marine terraces. Two aquifers have been identified in the area. The first is unconfined and occurs within the Quaternary sediments whereas the other is a deep confined aquifer occurring within the underlying Neogene marl series. Analysis of hydrochemical evolution over the past 30 years has indicated significant deterioration of quality owing to seawater intrusion and nitrate pollution. The various sources of pollution have rendered, to a large extent, shallow groundwater unsuitable not only for potable water supply but also for irrigation purposes. However, this is not the case for the deeper confined aquifer. Statistical analysis was used to explore the evolution of salinization during the years 1968 and 1998. In view of the alarming conditions caused by the documented groundwater quality deterioration, the need for integrated water resources management is stressed to maintain the socio-economic growth of the region studied.
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