2. Motivation
Estimation of travel time of water molecules (Transit-Time Distribution) from Rainfall to Outlet needs gauged river location for effective precipitation estimation
Transit-Time Distribution is a lumped characteristic of the catchment
Hypothesis
Use one gauged river location to derive effective precipitation
Assume a constant effective precipitation in a small catchment
Use this effective precipitation time series for ungauged river locations with tracer time series (d18O, d2H) to derive Transit-Time Distributions
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3. TRANSEP Isotopes Precipitation MEASURED RESULT
(actually a
calibration)
Transit Time Distributions (TTD)
Weiler et. al (2003), How does rainfall become runoff? A combined tracer and runoff transfer function approach, Water Resources Research
Isotopes & hydrograph
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4. TERENO Test-Site: Wüstebach (38 ha)
Outlet (gauged)
Points 1 – 16: Isotope tracer data
Assumption: peff = spatially invariable
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5. Hydrograph Simulation
Simulation of whole hydrograph time series
Qobs
Qsim
Summer: Overestimation
Winter: Underestimation
Precipitation
Time of Isotope Sampling
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6. Riparian Zone – Hillslope Hypothesis
Winter
Summer
Rosenbaum et. al (2012), Seasonal and event dynamics of spatial soil moisture patterns at the small catchment scale, Water Resources Research
SoilNet - Nodes
grafik machen mit SWC-abfluss (so wie PENNA)
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7. Soil Water Content – Runoff Relationship
Penna et. al (2011), The influence of soil moisture on threshold runoff generation processes in an alpine headwater catchment, Hydrology and Earth System Sciences
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8. Hydrograph Simulation
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9. Riparian Zone – Hillslope Hypothesis
Hydrologically-Active Residual Area (HARA)
peff
RMSE
RMSE low plateau
peff start of decline
Area 4-5 ha
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10. Response Time Distributions
Mean Response Time [days]
Summer 2009 (9) & 2010 (6)
Winter 2009/10 (21) & 2010/11 (19)
Summer 2011 (81)
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11. TRANSEP – Isotope Simulation
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12. Isotope Simulation
d18O Obs
d18O Sim
d18O Rain
peff
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13. Conclusions
Hydrograph simulation with TRANSEP indicates that the runoff active-catchment area changes with season
During Winter months the full catchment (38 ha) is active, whereas during Summer only appr. 13% (4-5 ha) of the catchment remains active
Due to this change in runoff active-catchment area, the slow runoff component reacts faster to precipitation in Summer than in Winter
Taking these points into account allows for succesful modelling of non-event isotope tracer time series and determination of Transit-Time Distrubtions
Next step: Modelling of all ungauged isotope tracer sampling locations and spatial analysis
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14. Thank you for your attention.
Terrestrial Environmental Observatories
Eifel/Niederrheinische Bucht
More information and data at
TR 32 – Subproject C1
Acknowledgements to Transregional Collaborative Research Centre 32 (TR32)
More information at
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