Karst Springs of Alashtar, Iran

Abstract

Področje Alaštar je v zahodnem delu Irana. Večji del ozemlja je iz jursko-krednih dolomitov in apnencev. Tam je pet kraških izvirov: Amir, Čenare, Zaz, Honam in Papi. Vsi izviri, razen Papija, so v jursko-krednih apnencih. Izvir Papi je na stiku jursko-krednih apnencev z lapornatimi apnenci eocenske starosti. Glavne žile, ki dovajajo vodo izvirom, so prelomi in tektonske linije. Ti izviri so razlog, da po ravnini tečejo reke. Prelome lahko razdelimo v narive in normalne prelome. Prelomi se najčešče javljajo na stiku apnencev z ravnino, v čemer je vzrok, da ima ta strukturo tektonskega jarka. Izviri igrajo veliko vlogo pri napajanju ravnine. Zaradi prelomov in izvirov ima ravninski vodonosnik veliko vode. Tako dajejo nekatere vrtine preko 60 l vode v sekundi. Pretoki izvirov se preko leta precej spreminjajo. Vseeno uvrščajo izvire Amir, Čenare in Honam med stalne izvire. Skupna letna količina vode je 111 milijonov m3 . Hidrokemične analize kažejo, da so vsi izviri karbonatnega tipa.

Alashtar area is situated in the western part of Iran. The Jurassic Cretaceous dolomitic limestone covers most of the area. There are 5 karstic springs named as Amir, Chenare, Zaz, Honam and Papi. All the springs except the Papi emerge from the Jurassic-Cretaceous limestone.The Papi Spring discharges at the contact of the Jurassic-Cretaceous and the Marly limestone of Eocene age. The springs show variation of discharge during the different periods. Faults and the lineaments are the main avenues for the emergence of the springs. The springs are responsible for the rivers in the plain. The fractures are classified as thrust and normal faults. The faults are mostly formed at the junction of the surrounding carbonate rocks which give a graben structure to the plain. The springs have an important role in recharging the plain. It is due to the fractures and the springs that the plain aquifer has a high potential of water. The discharge of some of the wells is more than 60 l/s.The discharge of the springs varies considerably during the year. Out of these, the Amir , Chenare and Honam springs are considered as permanent springs. The annual discharge of the springs is 111 MCM. The hydrochemical analyses of the springs show that all of them are of carbonate type.