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Revisiting Michael Bonell’s humid tropical rainforest catchments: isotope tracers reveal seasonal and inter-annual shifts in catchment hydrology
  • Hanshe Lim,
  • Niels Munksgaard,
  • Michael Bird
Hanshe Lim
James Cook University College of Science and Engineering

Corresponding Author:[email protected]

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Niels Munksgaard
James Cook University
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Michael Bird
James Cook University
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It has been almost 50 years since Mike Bonell’s foundational work in the humid tropics, kickstarting the field of tropical hydrology. In order to expand on this work and build a more generalized hydrological understanding of steep rainforest catchments, we studied the seasonal and inter-annual evolution of hydrological response from two catchments with similar characteristics to those studied by Bonell. Both hydrometric and water stable isotope data were collected at relatively high frequencies during one wet season (Thompson Creek) and a three-year period (Atika Creek). The longer dataset spans a wide range of environmental conditions experienced in the humid tropics, including events that cover the wetting-up transitional period of the wet season, ENSO events and tropical cyclones. Both catchments displayed fast streamflow response to rainfall with the shallow upper soil profile responding quickly to rainfall at Atika Creek. New findings from this study include the importance of pre-event water (>50%) for overall event flows, especially when the catchment was wet. Rainfall, surface runoff and groundwater isotope compositions varied between rainfall events with the most complex mixing plots observed for multi-peak events that occurred at the start of the wet season and after a dry period within the wet season. Inter-annual variability in catchment hydrology reflected changing ENSO conditions and the 2020-21 La Ninã wet season was characterized by several tropical cyclone events which generated the most 18O-depleted rainfall and streamflow isotope values. Our findings highlight the requirement for high frequency multi-source sampling to accurately interpret catchment behavior. We propose a conceptual model to describe the seasonal evolution of streamflow response in steep rainforest catchments.
28 Jan 2022Submitted to Hydrological Processes
29 Jan 2022Submission Checks Completed
29 Jan 2022Assigned to Editor
29 Jan 2022Reviewer(s) Assigned
30 Mar 2022Review(s) Completed, Editorial Evaluation Pending
31 Mar 2022Editorial Decision: Revise Major
05 Jun 20221st Revision Received
06 Jun 2022Submission Checks Completed
06 Jun 2022Assigned to Editor
06 Jun 2022Reviewer(s) Assigned
06 Sep 2022Review(s) Completed, Editorial Evaluation Pending
07 Sep 2022Editorial Decision: Revise Minor
27 Sep 20222nd Revision Received
27 Sep 2022Assigned to Editor
27 Sep 2022Submission Checks Completed
27 Sep 2022Reviewer(s) Assigned
28 Sep 2022Review(s) Completed, Editorial Evaluation Pending
28 Sep 2022Editorial Decision: Accept