 |
| Titel |
Hydrological functioning of the mountainous peatlands - oxygen isotopes study |
| VerfasserIn |
Martin Sanda, Michal Dohnal, Milena Cislerova |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053484
|
|
|
|
|
|
| Zusammenfassung |
| Mountainous peatlands are important hydrological component of the headwater catchments
in Jizera Mountains, The Czech Republic. The hillslopes of experimental catchments
UhlíÅská (1.78 km2) and the Nature Reserve of Mires of Jizera (1.3 km2) are formed on
paleozolic crystalline bedrock overlaid by shallow highly permeable Cambisols and Podzols,
whereas the thick saturated alluvial deposits in the valley are overlaid by Histosols. Standard
meteorological and hydrological monitoring at these test sites is supplemented by
measurements of soil moisture, soil pore water suction, and the water table fluctuation in the
saturated riparian zone of the streams. Since 2006, the water sampling to detect the 18O and
2H isotopes is performed throughout the catchments on hourly to monthly time
basis.
The detailed dataset of water quantity (precipitation, outflow, soil suction, soil moisture,
groundwater table) linked to environmental tracers (oxygen isotopes, pH, electrolytic
conductivity, UV absorbance 254 nm for organic matter and silica content in waters) gathered
since then, enables to seek answers to frequently posed questions: What are the sources and
flowpaths of water in wetlands? What is the water residence time of water in the catchment or
its subsections? How the water bodies interact? Conservative nature of the stable isotopes
enables to balance water masses in the wetlands as a binding element of streamflow and
groundwater.
Multiple methods have been applied: simple plotting of data with high time resolution,
cross-plots linking e.g. streamflow with tracer data, or two tracer datasets comparison (e.g.
oxygen isotopes and silica). Simple and advanced modeling tools were used: the linear
reservoir model and FLOWPC model to estimate the catchment water residence time;
Advanced tools as the S1D numerical code based on Richards’ equation to simulate the
vertical 1D soil water flow and the advection-dispersion transport of stable oxygen isotope
18O; the groundwater flow models MODFLOW/MODPATH/MT3D have been used to test
posed hypotheses.
Based on the data analysis, the water regime features can be summarized:
The examined peatlands are primarily groundwater driven fens, with the secondary
precipitation impact via infiltration. Baseflow is dominantly controlled by the groundwater
discharge. During rainfall–runoff episodes, water is conducted in the weathered zone
of mineral soils on the upslopes along the slope, percolates into the aquifer and
discharges into the peatlands on its lower interface with the sedimentary aquifer. The
pre-event water, stored in the valley wetlands, the upslope saturated areas or the
sedimentary aquifer, is replaced/pushed into the stream due to the pressure gradients
mobilized by the water infiltrating on the hillslopes. The mean residence time of
water in the catchment examined by simple linear reservoir model is in the range of
7 months, while the application of FLOWPC model finds two pools of water of
approximately similar volume (groundwater, and weathered soil mantle of the upslopes
together with wetlands in the valley). The isotopic separation proves 50-75% of
pre-event water in the flood flow. The S1D simulations of flow and transport in
Cambisols and Histosols demonstrate intensive mixing even when preferential flow
occuring in Cambisols is included. The groundwater flow models employing the stable
isotopes data show that even the shallow layer of the aquifer water masses are well
mixed.
This study is a part of IAEA Coordinate Research “Isotopic Techniques for Assessment
of Hydrological Processes in Wetlands”, comprising 14 countries on 6 continents, where
further questions regarding element cycling, chemical processes and biophysical indicators
with the support of isotopic tools are targeted as well. The research is supported by
IAEA research contract 14007 and by the Czech Science Foundation projects No.
205/09/0831, No. 205/08/1174, Czech Ministry of Environment No. SP/2e7/229/07. |
|
|
|
|
|
|