Chemical assessment of dam water irrigation effects on groundwater qualities in Bigherd plain, Fars Province, Iran

In this study the effect of irrigation by dam water in Bigherd area ( Fars Province, Iran) on groundwater quality 1 and 3 years after dam construction was investigated. To conduct this study the major ion concentrations, including HCO3-, Ca2+, Mg2+, Na+, K+, SO42- and Cl- and water levels in ten water wells and the dam reservoir were measured during two periods ( June 2009 and June 2011), analyzed by factor analysis and plotted in water quality charts. The results of factor analysis show that most of the dissolved ions including Mg2+, Ca2+, SO42-, Cl- and HCO3-, particularly in 2009, were mainly originated from carbonate and evaporitic formations as well as from the playa lake ( Factor 1). In 2011, elevated salinity levels were found to be mainly related to intense evaporation during irrigation that are proportional to Na+ and K+ concentrations ( Factor 2) and depend on the type of crop and irrigation method. It was also found that the surface waters from deeper origins had less of an effect on groundwater recharge compared to upstream carbonate aquifers.