ORIGINAL PAPER Determination of origin and distribution of saline water in the aquifer of Kharg Island, Iran Ali Akbar Shahsavari & Kamal Khodaei & Farhad Asadian & Mohamad Nakhaei & Ali Sardar & Abolfazl Moradi & Rahele Hatefi & Seyed Mohammad Zamanzadeh Received: 22 January 2014 /Accepted: 29 April 2014 # Saudi Society for Geosciences 2014 Abstract Kharg Island with an area about 21.3 km 2 is located between 29° 12′ 22″ to 29° 16′ 29″ northern latitudes and 50° 16′ 54″ to 50° 20′ 12″ eastern longitudes. It is located 58 km to the northwest of Bushehr City in the southwest of Iran. The target of present paper is determination of origin and distribu- tion of salt water in the shallow Kharg aquifer using hydrochemical and geophysical tools. More than 50 % of the island’ s surface is covered by limestone. General direction of groundwater flow in the aquifer is from highlands to the eastern and the northern coasts. Exploitation of groundwater is carried out by shallow wells on the eastern part of Kharg Island. Sampling operations were conducted in 27 wells in May 2010. Saltwater intrusion mapping was conducted on the aquifer through combining the results of geophysical and hydrochemical studies. Hydrochemical factors such as bro- mide, bicarbonate, carbonate and chloride ions, electrical con- ductivity, and chloride to strontium ratio in addition to appar- ent resistivity confirmed similar seawater intrusion pattern in different parts of the aquifer. The results show that seawater is the main source of groundwater salinity but via two difference mechanism. The first mechanism of seawater intrusion is taking place in shore line. The second one is due to upconing as a result of extraordinary exploitation of product wells located in the west part of Kharg aquifer. Keywords Kharg Island . Groundwater . Seawater intrusion Introduction Saltwater intrusion is a natural process, and bound to occur but it becomes an environmental problem when excessive pumping of fresh water from an aquifer takes place (Soni and Pujari 2010). This situation occurs nearly in all popu- lated coastal areas. In coastal aquifers, the investigation of groundwater flow at regional scale is complicated because a minor spatial variation in groundwater density has a substantial effect on groundwater flow rates and patterns. The fact that it is difficult to understand saltwater intrusions mechanism comprehensively is because of variable natural factors and dynamic characteristics of involved parameters (CMRI 2007). Groundwater flow systems along the coastal zones are characterized by flow paths that range from a few kilometers to several hundred kilometers. The seaward limit of fresh water in the coastal aquifers is controlled by a number of factors, including the amount of fresh water flowing through each aquifer, the thickness and hydraulic properties of each aquifer and adjacent confining units, the current geographic distribution of saline surface water, and the geologic history of global sea-level fluctuations (Barlow and Reichard 2010). The hydrochemical characteristic of groundwater is the direct basis for the judgment on seawa- ter intrusion. The most commonly used method is measur- ing the concentration of Cl - , which is the most important and stable macroelement in seawater and most sensitive to seawater intrusion (Zesheng 1992). The conductivity and resistivity are also used as subsidiary indexes (Zhumei A. A. Shahsavari (*) : K. Khodaei : F. Asadian : R. Hatefi Department of Geology, Research Institute of Applied Science, ACECR, Shahid Beheshti University, Tehran, Iran e-mail: aliakbar.shahsavari@gmail.com M. Nakhaei Faculty of Geology, Kharazmi University, Tehran, Iran A. Sardar Iranian Oil Terminals Company, Tehran, Iran A. Moradi National Iranian Oil Company, Tehran, Iran S. M. Zamanzadeh Faculty of Geography, University of Tehran, Tehran, Iran Arab J Geosci DOI 10.1007/s12517-014-1450-7