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| Titel |
Continuous radon measurements to determine surface water / groundwater interactions in upper catchments |
| VerfasserIn |
Harald Hofmann, Ian Cartwright, Benjamin Gilfedder |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078916
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| Zusammenfassung |
| Perennial rivers flow all year, even during long periods of drought. From baseflow separation
analysis, it is known that approximately 10 to 40% of the total discharge during dry periods is
derived from the adjacent riverbanks and the regional groundwater in the lowland areas of
rivers. However, these amounts do not even constitute half of the total discharge. This
suggests that other reservoirs within the catchment hold water from wetter seasons
and release them slowly during the rest of the year. While the volume of small
alluvial deposits in mountain valleys and the groundwater can only account for a
fraction of the ‘missing’ discharge components, the soil cover has a large capacity
to store and release water, but is often neglected in traditional hydrogeological
studies.
Hydrogeochemical tracers are often used to determine the contributions from upper
catchment reservoirs; however, sampling intervals are often too large to show all of the
process involved in the stream flow generation process. 222Rn is a naturally produced
radioactive isotopic tracer that is commonly used to quantify groundwater discharge to
streams, rivers, and wetlands. Traditional sampling and analysis techniques are usually
confined to point measurements taken at a specific time. However, it is difficult to constrain
short- or medium-term processes occurring at the groundwater-surface water interface using
single measurements. We have developed a new technique to extract dissolved gases from
surface water, which allows continuous 222Rn and CO2 measurements. The technique is ideal
for determining the time scales of groundwater discharge and interflow to upper catchment
creeks.
The first results from the continuous measurement techniques in combination with
continuous electrical conductivity measurements and weekly sampling for major ion
chemistry, stable isotopes, DIC and Si in a small headwater catchment in Australia (Lyrebird
Creek Catchment, Victoria, Australia) show that direct continuous measurements capture
variations in runoff processes and related chemistry changes in short-time scales ( |
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