Stable isotope composition in precipitation and groundwater of Shwan Sub-Basin, Kirkuk governorate, northeast of Iraq

Abstract

Stable isotope composition of δ2H and δ18O were investigated in the water resources of the Shwan sub-Basin northeast of Iraq. The study objects conceived the possible factors that affect the stable isotopes’ composition in precipitation additionally to achieve information concerning recharge processes and estimate the groundwater recharge sources. In this study, four precipitation samples were collected at the study area for the 2020–2021 hydrological year. Thirty-two groundwater samples and one surface water sample from Lesser Zab River (LZR) were collected during the same period for two sampling seasons. The results of observed meteorological data show a very little amount of precipitation for the sampling year. This year is considered a dry hydrological year with total annual precipitation of 100.62 mm compared with the previous 40 hydrological years with total annual precipitation of 325.43 mm. The isotopic composition in precipitation was highly varied as it primarily depends on environmental conditions. The depleted values are recognized with the increasing precipitation amount, whereas the enriched values were the most affected by evaporation. Back trajectory analysis revealed that stable isotopes in precipitation are primarily influenced by air masses and moisture sources. The sources of the trajectory that came from the Mediterranean Sea, Arabian Gulf and the Red Sea would lead to variations in the values of precipitation stable isotope. Stable isotope values in groundwater showed that the samples for both periods are located between East Mediterranean Water Line (EMWL) and Global Meteoric Water Line (GMWL) close to the Local Meteoric Water Line (LMWL) indicating that the groundwater recharge is mainly through precipitation. Groundwater recharges by an indirect recharge mechanism from the LZR, based on stable isotope similarity between depleted stable isotopes in groundwater and river water. The estimated groundwater recharge based on weighted oxygen isotopes is about 9.2% of annual rainfall infers that the recharge during the sampling year was very low. The low recharge value experiences dry weather conditions from low precipitation amounts besides increasing evaporation during the current study.

Hydrogeochemical characteristics and evaluation of groundwater resources of Jilin Province, China

“…This may be due to the isotope imbalance between atmospheric precipitation and rocks, and the oxygen isotope exchange between water and rock minerals, resulting in the enrichment of heavy isotopes in groundwater (Strohmenger et al, 2022;Zhou et al, 2022a,b). Oxygen isotopes in Region 2 drift to the left of the precipitation line, indicating that the precipitation in the study area may have experienced certain evaporation before reaching the surface, resulting in light oxygen isotope values (Ren et al, 2018;Al-Gburi et al, 2022;Su et al, 2022). The oxygen isotope values in volcanic areas are obviously biased and are distributed in the upper right of the precipitation line.…”

Analysis of Stable Isotopes ¹⁸O and ²H and Sodium Adsorption Ratio (SAR) for Groundwater Studies in Coastal Area in Semarang City, Central Java Province Indonesia

“…Stable isotopes have been widely used as tracers in groundwater studies [8]. By leveraging isotope hydrogeology, this method provides valuable insights into the composition of stable isotopes found in precipitation obtained from fractionation during seawater evaporation [9]. Studies on deep-water isotopes have also been used to determine the origin of groundwater and its association with rainwater.…”