Spatiotemporal patterns of stable isotopes and hydrochemistry in springs and river flow of the upper Karkheh River Basin, Iran

Abstract

Karst springs of the Zagros Mountains contribute a significant amount to agricultural and human water demands of western and south-western Iran. For an adequate management of available water resources in semi-arid and arid regions, sufficient hydrological monitoring is needed, and hydro-chemical and isotope hydrological data provide important additional information. About 350 water samples were collected from precipitation, river water, and karst springs of the upper part of the Karkheh River Basin (20,895 km²) located between 33°35^′ and 34°55^′ North and 46°22^′ and 49°10^′ East with elevations ranging from 928 to 3563 m above sea level. Sampling was conducted in monthly time resolution from August 2011 to July 2012. All samples were analysed for hydro-chemical parameters (pH, electrical conductivity, and major ions) and stable isotopes (deuterium, oxygen-18). Isotope values of precipitation indicate a local meteoric water line (Zagros MWL δ²H=6.8 δ¹⁸O+10.1; R²=0.99) situated between the Mediterranean MWL and Global MWL. Spring and river water isotope values vary between−7.1 and−4.1 ‰, and−38 and−25 ‰ for δ¹⁸O and δ²H, respectively, responding to winter snowmelt and evaporation. This work implements stable isotopes and hydro-chemical information of springs and river water to understand hydrological and hydro-geological interrelations in karstic semi-arid areas and helps to improve the current water resources management practices of western Iran.

Keywords:

• evaporation
• hydrogen-2
• Iran
• karst
• oxygen-18
• river water
• spring water
• upper Karkheh Basin

Acknowledgements

The authors also appreciate the help of Kamran Sohrabi, Afshar Bahrami, Komail Safaniya, Sajad Almasi, Shahin Heydari, Kazem Ghalkhanbaz, Kaveh Jarareh, and Osman Mohammadi during the field campaigns.

Funding

The authors gratefully acknowledge financial support from German-Iran Alumni network (GIAN) and German Academic Exchange Service (DAAD) for field visits to Iran for PK. The Ministry of Science, Research and Technology of Iran was paying a six-month visiting stipend to BGR for KO.