HYDROLOGICAL PROCESSES Hydrol. Process. 17, 2327–2345 (2003) Published online 2 April 2003 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/hyp.1245 Marine and human activity influences on the groundwater quality of southern Korinthos area (Greece) G. Stamatis 1 * and K. Voudouris 2 1 Institute of Mineralogy–Geology, Agricultural University of Athens, Iera Odos 75, GR-118 55, Athens, Greece 2 Department of Geology, University of Patras GR 261 10, Patras, Greece 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. Copyright  2003 John Wiley & Sons, Ltd. KEY WORDS Korinthos region; groundwater; hydrochemistry; seawater intrusion; nitrate pollution INTRODUCTION The region of Korinthos lies at the northeastern part of Peloponnese, Greece (Figure 1), and presents a relatively smooth geomorphological relief, which is surrounded by very long seashores. The shape of the region is almost like a peninsula, which is situated between the Gulf of Korinthiakos at the north and Saronikos Gulf at the east. The semi-arid climate prevailing in the region, with low annual precipitation, is responsible for the shortage of water resources for meeting the domestic and irrigation needs. The water requirements of the region considered have increased during the past decades owing to rapid urbanization, accelerated tourism development, agricultural activities and a continuous population increase since the 1950s. In summer time water demands increase owing to an influx of tourists. Most of the water demands are covered from the development of the unconfined aquifer, using a large number of shallow wells. However, since the 1980s increased demands for both potable and irrigation water have led to the exploitation of the deeper aquifers. The development of the deeper confined aquifer subsequently proved not to be the optimum solution for meeting the increasing water demands. The increasing number of deep boreholes, the lack of any protective measures and the inefficient water resources management, in conjunction with the decrease of direct groundwater recharge from precipitation following the 1989–1992 drought, has gradually resulted in deterioration of groundwater quality. Moreover the excessive pumping resulted in a progressive saline intrusion in the aquifers. This situation also can be attributed to the construction of the Canal of Korinthos, which brought * Correspondence to: G. Stamatis, Institute of Mineralogy– Geology, Agricultural University of Athens, Iera Odos 75, GR-118 55, Athens, Greece. E-mail: stamatis@aua.gr Received 11 March 2002 Copyright  2003 John Wiley & Sons, Ltd. Accepted 17 October 2002