Hydrogeological and hydrogeochemical investigation of Dorfak karstic basin,(Guilan province, northeast Rudbar)

Karstic aquifers make the main sources of groundwater in northeastern Rudbar.The present study attempts to investigate the hydrogeological and hydrogeochemical features of karst springs in the area and karst development by means of discharge data of Sefidab spring.In this study, the ability of the PHREEQC and Rock Ware AqQa softwares to calculate the saturation index and drawing water hydrochemical diagrams were used.The paper also investigate the spatial distribution of geochemical parameters of springs, and compare changes of these parameters with the slope in the region. Spatial distribution of geochemical parameters of the water showed that these parameters have significant changes due to the slope of the region.By drawing Piper diagram of the samples of spring water, it was unfolded that water samples are Ca-Hco3 water type and karstic origin of springs were confirmed. Such that saturation index indicates more water samples are under saturated than calcite, dolomite and Co2. By calculating the recession coefficients of Sefidab spring and comparing the values of these coefficients with provided classification by Malı´k and Vojtkova (2012), the development degree of karst was determined 5.5.In the the development degree of karst will exist complex discharge regime, a combination of one sub-regime with turbulent flow and two sub-regimes with laminar groundwater flow. Discharge sub-regime with turbulent flow is of short-term influence in comparison with overall groundwater discharge