Spatial distribution and controlling factors of surface water stable isotope values (δ18O and δ2H) across Kazakhstan, Central Asia

Huawu Wu; Jinglu Wu; Fan Song; Jilili Abuduwaili; A S Saparov; Xi Chen; Beibei Shen

doi:10.1016/j.scitotenv.2019.03.389

Spatial distribution and controlling factors of surface water stable isotope values (δ¹⁸O and δ²H) across Kazakhstan, Central Asia

Sci Total Environ. 2019 Aug 15:678:53-61. doi: 10.1016/j.scitotenv.2019.03.389. Epub 2019 Apr 18.

Authors

Huawu Wu¹, Jinglu Wu², Fan Song³, Jilili Abuduwaili⁴, A S Saparov⁵, Xi Chen⁴, Beibei Shen¹

Affiliations

¹ State Key Laboratory of Lake Science and Environment Research, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Ecology and Environment of Central Asia, Chinese Academy of Sciences, Urumqi 830011, China.
² State Key Laboratory of Lake Science and Environment Research, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Ecology and Environment of Central Asia, Chinese Academy of Sciences, Urumqi 830011, China. Electronic address: w.jinglu@niglas.ac.cn.
³ Information Center (Hydrology and Water Resources Monitoring and Forecasting Center), The Ministry of Water Resources of the People's Republic of China, Beijing 100053, China.
⁴ State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
⁵ Institute of Soil Science, Kazakhstan Ministry of Agriculture, Almaty 050060, Kazakhstan.

PMID: 31075603
DOI: 10.1016/j.scitotenv.2019.03.389

Abstract

Climate change is expected to alter hydrological and biogeochemical processes in Central Asia (CA), and surface water stable isotope values (δ¹⁸O and δ²H) can be used to examine these changes. Spatially extensive stable isotope data, however, are sparse, which constrains the understanding of hydrological processes in transboundary rivers across Kazakhstan. Therefore, we conducted a survey of surface water stable isotopes across the region. River and lake water isotope values exhibit spatial variability that was closely associated with isotope values of precipitation, physiographic factors, landscape characteristics, and local hydrological processes, e.g., evaporation and mixing of waters from different sources. River water was characterized by lower δ¹⁸O and δ²H values and higher d-excess relative to lake water, suggesting evaporative enrichment of lake water. Analysis of δ¹⁸O versus δ²H for rivers and lakes yielded distinct regressions, (river [RWL], δ²H = 6.08δ¹⁸O - 16.7, r² = 0.837, p < 0.001) and (lake [LWL], δ²H = 6.23δ¹⁸O - 22.1, r² = 0.924, p < 0.001). The slope and intercept of the RWL and LWL were slightly lower than the local meteoric water line [LMWL] (δ²H = 6.96 δ¹⁸O - 1.0, r² = 0.942, p < 0.001). River water δ¹⁸O showed a significant negative correlation with elevation and longitude, but not with latitude. The spatial distributions of δ¹⁸O and d-excess values showed a remarkable gradient from west to east across Kazakhstan that was associated with moisture moving from the Mediterranean region to Kazakhstan. We also found generally higher δ¹⁸O values and lower d-excess values in low-elevation areas because of high evaporation rate in Kazakhstan. These baseline data will be useful for documenting the effects of climate change on the hydrological cycle in Central Asia.

Keywords: Evaporative enrichment; Stable water isotopes; Tianshan Mountains; Transboundary river; d-excess.