Seasonal stream network expansion and contraction in Swiss headwater catchments
Abstract
It is well known that the flowing stream network expands in response to increasing catchment wetness conditions during rainfall events and contracts as the catchment dries out. However, still little is known about the occurrence and frequency of flow in different parts of the temporary stream network and connectivity of the temporary stream network to perennial streams. We, therefore, studied the changes in the occurrence of flow in the temporary stream network of eight small (0.12 - 0.68 km2) headwater catchments during the fall 2015 wetting up period to determine where flow occurs, how the flowing stream network expands and what the topographic characteristics are of the flowing stream sections. The studied catchments are located in two different pre-alpine areas in Switzerland and differ in terms of the mean annual precipitation and the degree of human influence on the channel network, particularly ditching and road related drainage features. The streams were mapped using repeated direct observations and classified into different flow types (flowing, weakly flowing, trickling, weakly trickling, standing water, dry). As the catchments wetted up in response to rainfall events after a dry summer, the flowing stream density increased up to five times, the connected stream density increased up to six times and the number of flowing stream heads increased up to ten times. Surface topography, particularly the upslope accumulated area and Topographic Wetness Index, and local storage areas could partly describe where flow occurred but stable channel heads at locations of springs, shallow soils and wetlands were common as well.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H23I1693V
- Keywords:
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- 0452 Instruments and techniques;
- BIOGEOSCIENCESDE: 1813 Eco-hydrology;
- HYDROLOGYDE: 1830 Groundwater/surface water interaction;
- HYDROLOGYDE: 1860 Streamflow;
- HYDROLOGY