Modify of Eugster & Hardie Brine Evolution Flow Diagram in the Base of Brine of Maharlou Lake

Maharlou lake located in southwest of Iran is an intra-continental sedimentary basin. Its area is about 280 km2 extended with an average water depth of 1.5 m during wet seasons. The water level in the lake is controlled by several factors such as runoff volume from Maharlou catchment, underground water seepage, and direct rainfall over the lake and also evaporation. Generally, hydrochemical analysis of water resources showed that the water types are mainly bicarbonates and sulfates due to geology of the surrounding areas. Hydrochemical investigation has been carried out for a time period between 1975 and 2002 using previously published analyses together with new collected water samples. 230 samples were collected during summer 2001, summer 2002 and spring 2005. Results show a change in the brine type through time; with an Mg-SO4-Cl type in 1970 to an Mg-Cl-SO4 type in 2001 and currently Na-Mg-Cl brine type, in recent time, which is comparable with Great Salt Lake in USA. Due to changes in diluted water compositions from HCO3 ≥ (Ca + Mg) to HCO3<< (Ca + Mg), the path of brine on the Eugster and Hardie flow diagram changes from row III to the path II, indicating that the bicarbonate water comes into the lake from a fault occurring in the lake floor.