Stable isotopes in river waters in the Tajik Pamirs: regional and temporal characteristics

Abstract

The Gunt River catchment in the Central Pamirs is a representative of the headwater catchments of the Aral Sea Basin. It covers 14,000 km(2), spanning altitudes between 2000 and 6700 m a.s.l. In a monitoring network, water samples were taken at 30 sampling points every month and analysed for the stable water isotopes ((18)O and (2)H). Our first results show δ(2)H values in the range from-131.2 to-94.9 ‰ and δ(18)O values from-18.0 to-14.0 ‰. The stable isotope patterns in the catchment seem to follow a systematic way, dominated by an altitude effect with a mean Δ δ(2)H=-3.6 ‰/100 m. The observed seasonal variations can be explained by geographical aspects such as the influence of different wind systems as well as melting processes.

The Doubly Labeled Water Method Produces Highly Reproducible Longitudinal Results in Nutrition Studies

“…Because the reproducibility results were obtained using isotope ratio MS, the results might not be applicable to DLW studies carried out using other instrumentation such as cavity ring-down spectroscopy (57)(58)(59)(60) or Fourier transform infrared spectroscopy (61,62). The long-term reproducibility of the DLW method using these other instruments will need to be documented.…”

The Global Network of Isotopes in Rivers (GNIR): integration of water isotopes in watershed observation and riverine research

“…Rivers were then grouped by δ 18 O minima in late spring and summer due to delayed seasonal snow-and glacier melt at higher altitudes (e.g. Meier et al, 2013). A second grouping was clustered by higher latitudes (> 30 • latitude) and δ 18 O minima in the winter months during the lowest air temperature (Dansgaard, 1964).…”

“…Alpine or high-latitude rivers may be ephemeral, dominated mostly by isotopically depleted snowmelt events (e.g. Friedman et al, 1992;Meier et al, 2013). Seasonal isotopic variations in rivers, nevertheless, can mirror annual variations in precipitation (e.g.…”

Bridging Glaciological and Hydrological Trends in the Pamir Mountains, Central Asia

“…This glacio-nival dry climate is induced by westerlies-dominated moisture supply, which causes a precipitation gradient from high values in the North-West Pamir to the lowest values in the East Pamirs [42]. The arid South-East Pamirs (north of the Karakoram) are characterized by a precipitation maximum in summer, whose potential origin is the subject of controversial discussions [20,43,44]. Precipitation in the East Pamirs is said to increase (seen in Global Precipitation Climatology Project (GPCP) data [4]) and expected to trigger glacial mass gain from the West Kunlun Shan up to the Pamirs [20].…”

“…The Gunt River Basin lies within a transition zone of strengthening westerlies and another mostly unknown climatic driver, partly called an "anomaly" [20,37]. Regionally different precipitation sources have been figured out based on stable isotope signatures in water samples [44]. The eastern part of the River Gunt catchment spans over the dry plateau of the Tajik East Pamirs, adjacent to the above-mentioned "meteorological anomaly".…”