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| Titel |
From rainfall to rivers: A comparison of modelled and measured stable water isotopes in precipitation and river catchments at a global scale |
| VerfasserIn |
Janine Halder, Stefan Terzer, Leonard I. Wassenaar, Luis Araguas-Araguas, Pradeep K. Aggarwal |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110699
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| Publikation (Nr.) |
 EGU/EGU2015-10726.pdf |
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| Zusammenfassung |
| Rivers are a crucial link in the global hydrological cycle as they discharge precipitation,
groundwater, and water stored in snowpacks and glaciers back to the world oceans. However,
there are essential gaps in hydrological data between rainfall, infiltration, and river discharge
to the world oceans. Stable water isotopes are used to trace sources of precipitation and river
water, unravel hydrological processes, as well as to assess the water balance of watersheds.
With the widespread adoption of laser absorption spectroscopy for water isotope analysis,
there is growing potential for an improved integration and application of isotope methods,
combined with traditional quantitative and qualitative hydrological studies of large
rivers.
The Global Network of Isotopes in Rivers (GNIR) has been established a decade ago and
aims to fill the informational data gaps between rainfall and river discharge. Here we report
the results of a preliminary evaluation of the GNIR data holdings for about 250 river
catchments, using measured and modelled stable water isotope compositions. A regionalized,
cluster-based precipitation isotope model (RCWIP) was used to compare measured to
predicted isotope compositions of riverine catchments. The results help to identify knowledge
gaps and to improve the understanding of catchment scale processes of our world river
basins.
Our analysis suggests that the global GNIR river stations can be clustered into 6 different
groups, as a function of their seasonal variation in stable isotope composition. A sinusoidal
function reveals that there are periodic phases within each river grouping, which shows that,
despite different catchment effects (e.g. river length, width, or amount of baseflow
contribution), direct seasonal run-off (isotopic) patterns are preserved. The periodicity of
the isotopic run-off signal, however, is dependent on river catchment latitude and
snow or glacier meltwater-contributions. The importance of direct precipitation and
run-off to the river discharge is confirmed by the strong co- variation of the isotope
composition of precipitation and river water on a global scale. However, as most of the
world’s rivers are impacted to some degree by natural or man-made reservoirs, mixing
processes of different water sources and of precipitation from different seasons are
observed. The model predicted isotope composition of rivers correlates well with
measured river isotope composition, however, some rivers strongly deviate. These
deviations are located in arid regions that experience intense evaporation processes, or
watersheds having important contributions from glacier-meltwater or permafrost. |
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