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| Titel |
Isotopic and hydrochemical characterisation of a (semi)-arid catchment in the Tajik Pamirs |
| VerfasserIn |
C. Ebert, M. Knoche, S. Geyer, T. Rödiger, W. Busch, R. Gloaguen, E. Pohl, K. Osenbrück, J. Baidulloeva, S. M. Weise |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068443
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| Zusammenfassung |
| In the (semi)-arid Central Asian mountains large rivers such as the Panj and Amu-Darya,
whose water is excessively exploited for irrigation purposes, are mainly fed from snow- and
glacial melt occurring in the Pamir and Tien Shan mountains (elevations over 5000 m). The
Pamir mountains receive their precipitation as snow in winter and spring due to westerly
winds originating in the Atlantic.
To understand the current and future key hydrological processes in an exemplary
drainage system in the Tajik Pamir we use a combination of isotope-hydrological and
hydrochemical methods, remote sensing techniques and enhanced hydrological simulation
models.
Investigations focus on the Gunt catchment (ca. 14,000 km2) in the (semi)-arid Tajik
Pamir, which is representative for the entire region. Almost in the middle of the catchment the
Gunt river crosses a naturally dammed reservoir, lake Yashikul with an extend of ca. 20
km.
As a first step towards estimation of the origin, interaction and dynamics of stream and
subsurface water components, samples for hydrochemical and isotopical analyses are and
will be taken monthly from river water and groundwater. Groundwater recharge and
discharge, streamflow components as well as water residence times will be characterised and
quantified by hydrochemical information (e.g. anions and cations) and stable and radioactive
environmental isotopes (e.g. 2H, 3H, 18O).
In several field campaigns beginning in August 2011 we sampled both water of the
stream, of selected tributaries and groundwater. Among others the stable water isotopes (δ2H
and δ18O) of the samples were analysed. Though results of the first Tritium screening of
selected sampling points show almost no distinctive features, stable isotopes highlight
variations between the different end members.
The isotopic data show that with an increasing flow length the Gunt water is enriched by
heavier stable water isotopes. One reason might be an altitude effect - from the sources to the
mouth it is an altitude range of about 4500Â m.
In comparison of the stream water, the tributaries and the groundwater there are
significant differences between these runoff components in their isotopical (2H and 18O)
signature. The data show that the isotopic composition of the Gunt below the lake reservoir
must be a result of a mixture of lake water and water from the following tributaries. The
different tributaries itself show an isotopic signal which leads to a possible distinction
between northern and southern tributaries.
Therefore the stable-isotopes data could be used to give an information about the altitude
of the different subbasins and their exposition to the westerlies.
The mineralization of the Gunt is higher than the concentrations of anions and cations in
the tributaries. This leads to the next notice, that the stream water, which is primarly marked
by the water of the lake Yashikul, is, with an increasing flow length, thinned out by the
tributaries’ water.
By using the hydrochemical data it should be possible to quantify the inflow contributions
of the different runoff components. |
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