Preprints
https://doi.org/10.5194/hess-2021-355
https://doi.org/10.5194/hess-2021-355
08 Jul 2021
 | 08 Jul 2021
Status: this discussion paper is a preprint. It has been under review for the journal Hydrology and Earth System Sciences (HESS). The manuscript was not accepted for further review after discussion.

Tandem use of transit time distribution and fraction of young water reveals the dynamic flow paths supporting streamflow at a mountain headwater catchment

Ravindra Dwivedi, Christopher Eastoe, John F. Knowles, Jennifer McIntosh, Thomas Meixner, Ty P. A. Ferre, Rebecca Minor, Greg Barron-Gafford, Nathan Abramson, Michael Stanley, and Jon Chorover

Abstract. Current understanding of the dynamic flow paths and subsurface water storages that support streamflow in mountain catchments is inhibited by the lack of long-term hydrologic data and the frequent use of single age tracers that are not applicable to older groundwater reservoirs. To address this, the current study used both multiple metrics and tracers to characterize the transient nature of flow paths with respect to change in catchment storage at Marshall Gulch, a sub-humid headwater catchment in the Santa Catalina Mountains, Arizona, USA. The fraction of streamflow that was untraceable using stable water isotope tracers was also estimated. A Gamma-type transit time distribution (TTD) was appropriate for deep groundwater analysis, but there were errors in the TTD shape parameters arising from the short record length of 3H in deep groundwater and stream water, and inconsistent seasonal cyclicity of the precipitation 3H time series data. Overall, the mean transit time calculated from 3H data was more than two decades greater than the mean transit time based on δ18O at the same site. The fraction of young water (Fyw) in shallow groundwater was estimated from δ18O time series data using weighted wavelet transform (WWT), iteratively re-weighted least squares (IRLS), and TTD-based methods. Estimates of Fyw depended on sampling frequency, the method of estimation, bedrock geology, hydroclimate, and factors affecting streamflow generation processes. The coupled use of Fyw and discharge sensitivity indicated highly dynamic flow paths that reorganized with changes in shallow catchment storage. The utility of 3H to determining Fyw in deeper groundwater was limited by data quality. Given that Fyw, discharge sensitivity, and mean transit time all yield unique information, this work demonstrates how co-application of multiple methods can yield a more complete understanding of the transient flow paths and observable storage volumes that contribute to streamflow in mountain headwater catchments.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Ravindra Dwivedi, Christopher Eastoe, John F. Knowles, Jennifer McIntosh, Thomas Meixner, Ty P. A. Ferre, Rebecca Minor, Greg Barron-Gafford, Nathan Abramson, Michael Stanley, and Jon Chorover

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-355', Anonymous Referee #1, 14 Oct 2021
    • AC3: 'Reply on RC1', Ravindra Dwivedi, 27 Oct 2021
  • RC2: 'Comment on hess-2021-355', Anonymous Referee #2, 15 Oct 2021
    • AC2: 'Reply on RC2', Ravindra Dwivedi, 27 Oct 2021
  • RC3: 'Comment on hess-2021-355, Anonymous Referee #', Anonymous Referee #3, 17 Oct 2021
    • AC1: 'Reply on RC3', Ravindra Dwivedi, 27 Oct 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-355', Anonymous Referee #1, 14 Oct 2021
    • AC3: 'Reply on RC1', Ravindra Dwivedi, 27 Oct 2021
  • RC2: 'Comment on hess-2021-355', Anonymous Referee #2, 15 Oct 2021
    • AC2: 'Reply on RC2', Ravindra Dwivedi, 27 Oct 2021
  • RC3: 'Comment on hess-2021-355, Anonymous Referee #', Anonymous Referee #3, 17 Oct 2021
    • AC1: 'Reply on RC3', Ravindra Dwivedi, 27 Oct 2021
Ravindra Dwivedi, Christopher Eastoe, John F. Knowles, Jennifer McIntosh, Thomas Meixner, Ty P. A. Ferre, Rebecca Minor, Greg Barron-Gafford, Nathan Abramson, Michael Stanley, and Jon Chorover
Ravindra Dwivedi, Christopher Eastoe, John F. Knowles, Jennifer McIntosh, Thomas Meixner, Ty P. A. Ferre, Rebecca Minor, Greg Barron-Gafford, Nathan Abramson, Michael Stanley, and Jon Chorover

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Short summary
This study applies multiple metrics including the fraction of young water and its discharge sensitivity and mean transit time using young as well as old groundwater age tracers to improve understanding of the dynamic nature of hydrologic flow paths at a sub-humid mountainous site. The results show that the aforementioned metrics yield unique information and they are helpful in understanding the nature of transient flow paths and observable storage volumes that contribute to streamflow.