Study of Karst Development Using Recession Coefficient, Spring Death Time and Chemical and Isotope Analysis in Parav-Bistoun Massif (Kermanshah Province-West of Iran)

Massif of Parav-Bistoun covered around 880 square kilometers of the thrust zone of Zagros Mountains and located in Kermanshah province. There are various kinds of karst Landforms such as jamas, uvulas', dolines, caves in this mountainous area. These landforms are under the influence of palaeoclimatic conditions. Nowadays, current climatic conditions in this area allows for development of karst landforms only in high altitudes, over 2500 meters. The rates of karst development are shown by correlation between precipitations and hydraulic coefficient, and also the rate of precipitations that influence the discharge of springs. Therefore, in this research, karst evolution in Parav-Bistoun massif has been evaluated based on hydrogeologic parameters. This work is based upon the Study of isotopic –chemical characters, Estimate of recession coefficient– volume of dynamic storage, Analysis and comparison between characteristics of major springs in Parav-Bistoun area, such as Sarab-Barnaj, Sarab-Bistoun, and Sarab-Tagh-e-Bostan, to other springs in the folded Zagros zone, such as Sarab-Shian and Sarab-Niloufar. In this research, our data for analysis belongs to the hydrological year of 1995. The result shows that the hydrograph of springs, that come out from karsic area, are more complicated. In fact the reason of low rate minerals in Tagh-e-Bostan spring are depended on the canalized recharge system and limited contact surface with the solution agent (water). High rate of tritium in the water of Parav-Bistoun massif springs, indicate their relations to characteristics of precipitation, rate of Carbon-14 and CO2 that indicated the rapid penetration of water through the karstified system and low level contact between water and bedrock and finally exist of canalized system in the study area. Evaluation of the rate of isotopic characters in springs, such as tritium, Carbon-14 and CO2 pressure show the karstified character of the area. Furthermore, death time of the springs, their recession coefficients and dynamic storage volume (in the Parave-Bistoon springs), implies high levels of karst development in the area and denote to conduit and canalized feeding system of the springs.