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Flow processes in headwater catchment using a combined hydrological, hydrochemical and isotopic approach

Martin Šanda1, Tomáš Vitvar1, Milena Císlerová1, Tomáš Vogel1, Jakub Jankovec1
1 Faculty of Civil Engineering, Czech Technical University in Prague

O 6.2 in Grundwasser-, Boden- und Oberflächenwasser-Interaktionen

30.05.2014, 11:20-11:40, H19, NW II

 

The subsurface water contribution to streamflow in small mountainous catchments dominated by rapid discharge variations is still poorly understood. To-date it has been attributed to a more or less delayed baseflow transmitted through preferential flow pathways. Combined hydrochemical and isotopic approach is tested to evaluate the sources of the groundwater in these catchments distinguishing its presumably younger and older components in stream runoff (Šanda et al., 2013).

In the catchment Uhlířská (1.78  km2) and in other nearby catchments in the Jizera Mountains, northern Czech Republic, the measurements of DOC, silica, stable hydrogen and oxygen isotopes, tritium, noble gases and CFC were conducted over the last five years in a set of sampling points. Samples in precipitation streamflow, baseflow, eventflow, soil lysimeters, subsurface soil trench and perennial groundwater boreholes down to 30 m depth were taken.

The results of analyses show that the baseflow contributes at about 67% to the streamflow and has a mean residence time of 12.3 months. Approximately 150-300 mm (10-20%) of annual precipitation were attributed to deep percolation. The baseflow is formed by soil water drainage in weathered layers on hillslopes during rainfall and snowmelt periods, in combination with the groundwater discharge from the valley deluviofluvial granitic sediments where the prevailing source is the infiltration of snowmelt water. Analysis of 20 runoff events and their hysteretic patterns demonstrated that the stormflow water has the residence time of about 4 months and is generated by the preferential flow on hillslopes together with the soil matrix drainage. The stormflow and snowmelt water flowing via preferential pathways of upslope mineral soils pushes the pre-event groundwater through the pathways in wetlands in direction to the stream, and the wetland can be therefore considered as groundwater-supplied. The groundwater apparent age obtained from 3He/3H and CFC data seems to result as a combination of the 70% admixture of a linear-piston flow pattern of about 80 years old, and the 30% admixture of exponentially distributed flow pattern with the mean residence time of about 4 years. This mechanism seems to be typical for groundwater-supplied headwater catchments of the Jizera Mountains. The isotopic and hydrochemical patterns of the headwaters are observed along the main stream course through the lowland. The multi-tracer approach allowed distinguishing different origins of groundwater. It demonstrated its importance on the runoff formation regarding mass transport.

The research is supported by Czech Science Foundation 205/09/0831, International Atomic Energy Agency, CRP contract no. 16335, and the EU program Ziel3/Cíl3 no. 100114993.



Šanda, M. & Vitvar, T. & Kulasová, A. & Jankovec, J. & Císlerová, M. 2013. Runoff formation in a humid, temperate headwater catchment using a combined hydrological, hydrochemical and isotopic approach (Jizera Mountains, Czech Republic). Hydrological Processes. DOI: 10.1002/hyp.9847



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Letzte Änderung 01.11.2013