Hidrogeokemična in izotopska karakterizacija ter ocena hidravličnega delovanja kompleksnega kraškega območja Izeh, provinca Khuzestan, jugozahodni Iran

Proper water resources management requires recognizing and evaluating the factors that affect the quantity and quality of water resources. The Ilam-Sarvak (Upper Cretaceous) and Asmari (Oligocene to Miocene) limestone- dolomite formations in the Zagros structural belt have formed a promising karst groundwater horizon. In the present study, the hydraulic relationship between the karst structures of the Izeh territory in the northeast of Khuzestan province was investigated using hydrogeochemical and isotopic information of springs and wells. The results enabled to understand various components influencing the recharge of water resources. In this study, samples were collected from the karst springs and wells of Mongasht, Shavish-Tanosh and Kamarderaz anticlines and Naal-e-Asbi (Horseshoe) syncline and meteoric water to understand the hydrochemical and isotopic characterization, and hydrogeological and hydraulic behavior of the Izeh karst system. The meteoric and groundwater samples were analyzed to determine major and minor ion concentrations and δ18O and δ2H isotope ratios. Isotopic content ranged from -31.6 to -2.9‰ and from -6.32 to -1.87‰ for δ2H and δ18O, respectively, and d-excess values were high and positive. The study of the isotopic content of water samples of springs and wells in the region shows three groups of water sources. The first group, related to the Mongasht anticline springs, has lower isotopic values, indicating that it is recharged by rainfall at high altitudes and snow melting. The isotopic value of the second group is richer than that of the first group, indicating rainfall recharge as well as groundwater mixing (ex­amples of Naal-e-Asbi syncline and Shavish-Tanosh anticline). The highest value in the third group (samples of Kamarderaz anticline) is attributed to evaporation and longer distance from the recharge site to the discharge point, as well as to the diffu­sion system. The trend of decrease in Sr+2 and increase in Ba+2 in the samples of dolomitic limestone formations (Shavish Ta­nosh and Mongasht anticlines) compared to the water samples of Kamarderaz anticline and Naal-e-Asbi syncline indicates the possibility that karst aquifers of the region are recharged from the Mongasht anticline and that there is a hydraulic relation­ship between these structures. D-excess and δ18O show a linear trend, illustrating the effect of altitude difference on isotopic content and recharge sources. The major and minor changes in the concentration of ions, the isotopic content of groundwa­ter and the relationship between TDS and δ18O and d-excess and δ18O indicate the mixing and recharging of karst aquifers (Shavish-Tanosh, Kamarderaz and Naal-e-Asbi aquifers) from the Mongasht karst aquifer and their hydraulic connection.Ustrezno gospodarjenje z vodnimi viri temelji na prepoznavanju in vrednotenju dejavnikov, ki vplivajo na količino in kakovost vodnih virov. Apnenčasto-dolomitni formaciji Ilam-Sarvak (zgornja kreda) in Asmari (oligocen do miocen) v strukturnem pasu Zagros sta oblikovali obetaven kraški vodonosnik. V tej študiji je bil hidravlični odnos med kraškimi strukturami ozemlja Izeh, ki je na severovzhodu province Khuzestan, ocenjen z uporabo hidrogeokemičnih in izotopskih analiz vode v izvirih in vodnjakih. Rezultati so omogočili razumevanje komponent, ki vplivajo na napajanje vodnih virov. Zbrani so bili vzorci iz kraških izvirov in vodnjakov antiklinal Mongašt, Šaviš-Tanoš, Kamarderaz, sinklinale Naal-e-Asbi (podkev) in meteorne vode, da bi razumeli hidrokemično in izotopsko karakterizacijo ter hidrogeološko in hidravlično delovanje kraškega sistema Izeh. Za določitev koncentracij glavnih in drugotnih ionov ter razmerja izotopov δ18O in δ2H so bili analizirani vzorci meteorne in podzemne vode. Vsebnosti izotopov so bile v razponu od ‒31,6 do ‒2,9 ‰ za δ2H in od ‒6,32 do ‒1,87 ‰ za δ18O, vrednosti devterijevega presežka pa so bile visoke in pozitivne. Analize vsebnosti izotopov v vzorcih vode iz izvirov in vodnjakov v regiji kažejo na tri skupine vodnih virov. Prva skupina, ki je povezana z izviri antiklinale Mongašt, ima nižje izotopske vrednosti, kar kaže, da se napaja s padavinami na višjih nadmorskih višinah in s talje­njem snega. Izotopska vrednost druge skupine je bogatejša od prve skupine, kar kaže na napajanje s padavinami in na mešanje podzemnih vod (primera sinklinale Naal-e-Asbi in antiklinale Šaviš-Tanoš). Najvišja vrednost v tretji skupini (vzorci antiklina­le Kamarderaz) je posledica delno izhlapevanja in daljše razdalje med mestoma napajanja in iztekanja ter delno difuzijskega siste­ma. Trend padanja Sr2+ in naraščanja Ba2+ v vzorcih v formacijah dolomitnih apnencev (antiklinali Šaviš-Tanoš in Mongašt) v pri­merjavi z vzorci vode antiklinale Kamarderaz in sinklinale Naal­-e-Asbi kaže na možnost, da se kraški vodonosniki napajajo iz območja antiklinale Mongašt, in na hidravlični odnos med temi strukturami. Devterijev presežek in δ18O kažeta linearni trend, ki ponazarja učinek višinske razlike na vsebnost izotopov in vire napajanja. Večje in manjše spremembe v koncentraciji ionov, vsebnosti izotopov v podzemni vodi in razmerju med TDS in δ18O ter devterijevim presežkom in δ18O kažejo na mešanje in napajanje kraških vodonosnikov (vodonosniki Šaviš-Tanoš, Ka­marderaz in Naal-e-Asbi) s kraškega vodonosnika Mongašt in na njihovo hidravlično povezanost

Assessment of the hydrogeochemical and isotopic characterization and hydraulic behavior of the Izeh complex karstic area, Khuzestan province, southwest Iran

Proper water resources management requires recognizing and evaluating the factors that affect the quantity and quality of water resources. The Ilam-Sarvak (Upper Cretaceous) and Asmari (Oligocene to Miocene) limestone- dolomite formations in the Zagros structural belt have formed a promising karst groundwater horizon. In the present study, the hydraulic relationship between the karst structures of the Izeh territory in the northeast of Khuzestan province was investigated using hydrogeochemical and isotopic information of springs and wells. The results enabled to understand various components influencing the recharge of water resources. In this study, samples were collected from the karst springs and wells of Mongasht, Shavish-Tanosh and Kamarderaz anticlines and Naal-e-Asbi (Horseshoe) syncline and meteoric water to understand the hydrochemical and isotopic characterization, and hydrogeological and hydraulic behavior of the Izeh karst system. The meteoric and groundwater samples were analyzed to determine major and minor ion concentrations and δ18O and δ2H isotope ratios. Isotopic content ranged from -31.6 to -2.9‰ and from -6.32 to -1.87‰ for δ2H and δ18O, respectively, and d-excess values were high and positive. The study of the isotopic content of water samples of springs and wells in the region shows three groups of water sources. The first group, related to the Mongasht anticline springs, has lower isotopic values, indicating that it is recharged by rainfall at high altitudes and snow melting. The isotopic value of the second group is richer than that of the first group, indicating rainfall recharge as well as groundwater mixing (ex­amples of Naal-e-Asbi syncline and Shavish-Tanosh anticline). The highest value in the third group (samples of Kamarderaz anticline) is attributed to evaporation and longer distance from the recharge site to the discharge point, as well as to the diffu­sion system. The trend of decrease in Sr+2 and increase in Ba+2 in the samples of dolomitic limestone formations (Shavish Ta­nosh and Mongasht anticlines) compared to the water samples of Kamarderaz anticline and Naal-e-Asbi syncline indicates the possibility that karst aquifers of the region are recharged from the Mongasht anticline and that there is a hydraulic relation­ship between these structures. D-excess and δ18O show a linear trend, illustrating the effect of altitude difference on isotopic content and recharge sources. The major and minor changes in the concentration of ions, the isotopic content of groundwa­ter and the relationship between TDS and δ18O and d-excess and δ18O indicate the mixing and recharging of karst aquifers (Shavish-Tanosh, Kamarderaz and Naal-e-Asbi aquifers) from the Mongasht karst aquifer and their hydraulic connection