Abstract

It is generally assumed that, in humid climates, the groundwater table is a subdued copy of the surface topography. However, the general groundwater table is unlikely to be affected by the microtopography as seen in high-resolution Digital Elevation Models (DEMs). So far, there has been little guidance on the best resolution DEM to use to determine the shape of the water table or the direction of shallow groundwater flow in headwater catchments. We, therefore, looked at the effects of DEM-smoothing and -aggregation on the calculated flow directions and derived catchment boundaries, and identified areas and landscape features for which the calculated flow directions are particularly sensitive to DEM smoothing or aggregation. For > 40 % of the area of the Krycklan study catchment, the calculated flow directions depend strongly on the degree of smoothing or aggregation of the DEM. The four main landscape features for which DEM smoothing or aggregation strongly affected the calculated flow directions were: local slopes in the opposite direction of the general slope, flat areas, ridges, and incised streambanks. To determine the effects of the changing flow directions on the derived catchment boundaries for the smoothed and aggregated DEMs, we calculated the drainage area for 40 locations, representing the outlets of catchments of varying sizes. The shape and size of the catchments of first-order streams were most affected by the processing of the DEM. These streams were often almost completely smoothed out during the DEM preprocessing steps. These shifts in catchment boundaries and drainage area would have a large effect on the water balance. This study thus highlights the need to carefully consider the effects of DEM smoothing or -aggregation on the calculated flow directions and drainage areas.

Keywords

Terrain analysis; DEM resolution; Groundwater table; Flow directions; Catchment hydrology; Boreal catchment

Published in

Journal of Hydrology
2021, Volume: 602, article number: 126717
Publisher: ELSEVIER

SLU Authors

• Bishop, Kevin

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

• Seibert, Jan

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    
  • University of Zürich

Associated SLU-program

Lakes and watercourses


UKÄ Subject classification

Oceanography, Hydrology, Water Resources


Publication identifier

DOI: https://doi.org/10.1016/j.jhydrol.2021.126717

Permanent link to this page (URI)

https://res.slu.se/id/publ/114249