Preprints
https://doi.org/10.5194/hess-2022-102
https://doi.org/10.5194/hess-2022-102
 
18 May 2022
18 May 2022
Status: this preprint is currently under review for the journal HESS.

Assessing runoff sensitivity of North American Prairie Pothole Region basins to wetland drainage using a basin classification–based virtual modeling approach

Christopher Spence1, Zhihua He2, Kevin Shook2, John Pomeroy2, Colin Whitfield3, and Jared Wolfe4 Christopher Spence et al.
  • 1Environment and Climate Change Canada, Saskatoon, Saskatchewan, Canada
  • 2Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
  • 3School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
  • 4Natural Resources Canada, Ottawa, Ontario, Canada

Abstract. Wetland drainage has been pervasive in the North American Prairie Pothole Region. There is strong evidence that this drainage increases hydrological connectivity of previously isolated wetlands and, in turn, streamflow response to precipitation. It can be hard to disentangle the role of climate from the influence of wetland drainage in observed streamflow records. In this study, a basin classification-based virtual modelling approach is described that can isolate these effects on runoff regimes. Three knowledge gaps were addressed. First, it was determined that the spatial pattern in which wetlands are drained has little influence on how much the runoff regime was altered. Second, no threshold could be identified below which wetland drainage has no effect on the streamflow regime, with drainage thresholds as low as 10 % by area were evaluated. Third, wetter regions were less sensitive to drainage as they tend to be better hydrologically connected even in the absence of drainage. Low flows were the least affected by drainage. During extremely wet years, runoff depths could double as the result of complete wetland removal. Simulated median annual runoff depths were the most responsive, potentially tripling under typical conditions with the high rates of wetland drainage. As storage capacity is removed from the landscape through wetland drainage, the size of the storage deficit of median years begins to decrease and to converge on those of the extreme wet years. Model simulations of flood frequency suggest that because of these changes in antecedent conditions, precipitation that once could generate a median event with wetland drainage can generate what would have been a maximum event without wetland drainage. The advantage of the basin classification-based virtual modelling approach employed here is that it simulated a long period that included a wide variety of precipitation and antecedent storage conditions across a diversity of wetland complexes. This has allowed seemingly disparate results of past research to be put into context and finds that conflicting results are often only because of differences in spatial scale and temporal scope of investigation. A conceptual framework is provided that shows, in general, how annual runoff in different climatic and drainage situations will likely respond to wetland drainage in the Prairie Pothole Region.

Christopher Spence et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2022-102', Anonymous Referee #1, 10 Jun 2022
    • AC1: 'Reply on RC1', Christopher Spence, 08 Aug 2022
  • RC2: 'Comment on hess-2022-102', Anonymous Referee #2, 22 Jun 2022
    • AC2: 'Reply on RC2', Christopher Spence, 08 Aug 2022

Christopher Spence et al.

Christopher Spence et al.

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Short summary
We learned how streamflow from small creeks could be altered by wetland removal in the Canadian Prairie, where this practice is pervasive. Every creek basin in the region was placed into one of seven groups. We selected one of these groups, and used its traits to simulate streamflow. The model worked well enough that we could trust the results even if we removed the wetlands. Wetland drainage did not change low flow amounts very much, but it doubled high flow and tripled average flow.