Evaluation of the Karstification of Dimeh and Pirghar karst masses based on spring hydrograph analysis

The shape of the karst spring hydrograph is a direct reflection of all the physical processes that affect the flow of underground water inside the aquifer. Especially, the shape and process of the recession curve provides important information about the storage and hydrogeomorphological characteristics of the aquifer mass supplying the spring. In this research, a quantitative analysis of the hydrogeological behavior of Dimeh and Pirghar karst springs in Chaharmahal and Bakhtiari provinces located in the high and folded zones of Zagros during the common statistical period (from 2000 to 2019) have been quantitatively analyzed. This analysis includes classification of karst aquifer, modeling of hydrograph recession curve and estimation of water volume stored in saturated and unsaturated part of karst aquifer by Mangin method. . Estimation of the coefficients of recession components of fast flow (αf), transfer flow (αif) and base flow (αb) of springs based on the analysis of 18 recession curves obtained αf = 0.004، αif = 0.016 and αb = 0.042 for Dime spring and αf = 0.007، αif = 0.038 and αb = 0.125 for Pirghar spring revealed that the degree of development of Pirghar spring is 7 and Dime spring is 5.5;The analysis of the time series results shows that the discharge of Dimeh spring is under influence of majority of open, medium-sized fissure and with smaller influence of connected conduits, but the Pirghar spring hasa a system developed karstification of the aquifer, formed by large open tectonic faults and karstic channels. The high transfer flow rate of Pirghar spring shows the point charge and channel system of the karst region.