21 Jan 2022
21 Jan 2022
Status: this preprint is currently under review for the journal HESS.

Predicting soil moisture across a heterogeneous boreal catchment using terrain indices

Johannes Larson, William Lidberg, Anneli M. Ågren, and Hjalmar Laudon Johannes Larson et al.
  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, 901 83, Sweden

Abstract. Soil moisture has important implications for drought and flooding forecasting, forest fire prediction and water supply management. However, mapping soil moisture has remained a scientific challenge due to forest canopy cover and small-scale variations in soil moisture conditions. Digital terrain analysis has been suggested as a way forward to model soil moisture variability across landscapes, and multiple digital terrain indices have been developed. However, the performance of these terrain indices depends on the resolution of the digital elevation models used and, in many cases, user-defined index-specific thresholds. In this study, we compared soil moisture predictions using nine different terrain indices and available soil wetness maps, at varying resolutions and user-defined thresholds, with a field dataset of soil moisture registered in five classes from a forest survey covering a boreal landscape. We found that topography could explain the spatial variation in soil moisture conditions but the effects of changing DEM resolution and user-defined thresholds severely affected the performance of the soil moisture modelling. These results demonstrate that modelled soil moisture conditions need to be validated, as selecting unsuitable DEM resolution or user-defined threshold can give ambiguous and even incorrect results. Challenges caused by heterogeneous soil types within the study area highlight the need for local knowledge when interpreting the modelled results.

Johannes Larson et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-560', Anonymous Referee #1, 17 Feb 2022 reply
    • CC1: 'Reply on RC1', Jose Gutierrez Lopez, 23 Feb 2022 reply

Johannes Larson et al.

Johannes Larson et al.


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Short summary
Terrain indices constitute a good candidate for modeling the spatial variation of soil moisture conditions in many landscapes. In this study, we evaluate 9 terrain indices on varying DEM resolution and user-defined thresholds with validation using an extensive field soil moisture class inventory. We demonstrate the importance of field validation for selecting the appropriate DEM resolution and user-defined thresholds and that failing to do so can result in ambiguous and incorrect results.