Chemistry of the Karst Sarabkalan Spring, Iran, and Controls of PDO and ENSO Climate Indices on It

Abstract

The Sarabkalan Spring serves as a primary water supply to irrigation and domestic use in the Sirvan Region, Iran. As it has a highly variable discharge, understanding its teleconnections with large‐scale climate variability is crucial. In this study, we first characterize the springshed and its corresponding karst aquifer system using genetic algorithm analysis on the spring discharge, water balance calculations, temporal variations of physicochemical parameters, and stable isotopes along with considering its geological settings. Then, the large‐scale climate indices teleconnections with precipitation and spring discharge are studied using wavelet analysis. Results reveal that the springshed contains two karst subaquifers resulting from geological and morphological settings. Unlike most developed karst systems in Zagros, which show one peak, the spring has two principal flow peaks over most hydrological years where the second peak occurs over the dry season. It takes ∼99 d (from lag correlation over 2008‐2019) and ∼145 d (from δ18O measurements over 2018‐2019) for rain water to reach the Sarabkalan Spring. Moreover, intense precipitations would result in an increase in discharge and a decrease in electrical conductivity, Ca + Mg, HCO3, SO4, Cl, ionic strength, and δ18O of the spring because of the developed karst conduit(s). It is further found that a positive Pacific Decadal Oscillation phase coupled with El Niño causes an increase in both the precipitation and spring discharge, signifying the influence of the atmospheric circulations of the Pacific Ocean on the spring behavior.

Large-scale climate variability footprint in water levels of alluvial aquifers across Iran

“…In that study, we found that the Pacific-based climate oscillations (PDO and, to lesser magnitude, ENSO) have a more powerful influence than the Atlantic-based oscillations (NAO and AMO) on the variability in the groundwater levels. Moreover, Rezaei (2020) explored the teleconnection between ENSO and PDO climate indices and a karst Sarabkalan Spring's discharge in the southwest of Iran with a fast-slow flow system. In this work, evidence is presented which shows a positive PDO phase coupled with El Nino increased both the precipitation and spring discharge.…”