BayCEER Workshop 2016

Run-off response to spring snowmelt of an alpine catchment in the Italian Dolomites

P 3.3 in Water and the environment: From biosphere to geosphere

Introduction

Water supply of alpine environments strongly depends on the reservoir provided by spring snowmelt. Hydrological tracers can be used to identify and quantify the proportions of snowmelt and other sources of a catchments runoff. Thereby they may help to better understand the processes behind the response of the catchment to, e.g. climate change. The objectives of this study were i) to distinguish between the different hydrological end-members of runoff, ii) to quantify the contribution of snowmelt to streamflow, and iii) to get more detailed information about the role of groundwater.

Material & Methods

During a field work campaign, a high resolution snowmelt-event sampling was conducted. The research area, a small alpine catchment, is located at the Dolomites. Over 500 samples of streamwater, soilwater, shallow and deep groundwater and snowmelt were collected. The samples were analyzed for major anions, cations and water isotopes ²H/¹⁸O. In addition, measurements of pH, EC, groundwater level and streamflow completed the dataset. To investigate deep groundwater influence in more detail, ²²²Rn concentrations were measured continuously.

Results & Conclusions

Time series analysis of different tracers in comparison to streamflow suggested, that catchment runoff is dominated by water with higher tracer concentrations prior to and after the snowmelt event. During the event these concentrations decreased with increasing outflow suggesting a higher impact of eventwater (surface/upper soil horizons). End-member mixing analysis suggested, that deep and shallow groundwaters play the most important role in the composition of the streamwater. In contrast, snowmelt and soilwater don’t seem to play a major role. Analysis of continuous ²²²Rn measurements revealed a negative correlation between streamflow and ²²²Rn concentration, showing that peak streamflow during snowmelt is mainly influenced by ²²²Rn depleted water and not by increased groundwater inflow.

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Keywords: Alpine catchment, catchment hydrology, water stable isotopes, hydrograph separation, end-member mixing analysis, radon detection