This study was carried out between October 2007 and September 2008 to determine seawater intrusion in the right bank of the Bafra Plain, Turkey. Monthly water samples were taken from 28 groundwater wells used for irrigation water supply, and EC, pH, Na<Superscript>+</Superscript>, Ca<Superscript>2+</Superscript>, K<Superscript>+</Superscript>, Mg<Superscript>2+</Superscript>, CO<Stack> <Subscript>3</Subscript> <Superscript>2−</Superscript> </Stack> <Subscript>,</Subscript> HCO<Stack> <Subscript>3</Subscript> <Superscript>−</Superscript> </Stack> <Subscript>,</Subscript> Cl<Superscript>−</Superscript> and SO<Stack> <Subscript>4</Subscript> <Superscript>2−</Superscript> </Stack> levels were measured. <Superscript>18</Superscript>O, D and T analysis were performed using water samples taken in August 2008. TDS, EC, Cl<Superscript>−</Superscript> and Na<Superscript>+</Superscript> levels of some wells were extremely high, and correlations between Cl<Superscript>−</Superscript> and TDS, EC and Na<Superscript>+</Superscript> values were also very high. A Piper diagram constructed from average annual data indicated various levels of seawater intrusion, and a correlation was observed between seawater intrusion rates and water table heights, with intrusion rates decreasing in line with increases in water table heights above sea level (asl). Graphs of <Superscript>18</Superscript>O and D values indicated all wells to be close to the seawater-freshwater mixture line. A linear relationship was observed between <Superscript>18</Superscript>O and Cl<Superscript>−</Superscript>, EC and SO<Subscript>4</Subscript> <Superscript>2−</Superscript>. Copyright Springer Science+Business Media B.V. 2012
