the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
21 Jan 2021
21 Jan 2021
Taking theory to the field: streamflow generation mechanisms in an intermittent, Mediterranean catchment
- College of Science and Engineering, Flinders University, Adelaide, 5001, Australia
- College of Science and Engineering, Flinders University, Adelaide, 5001, Australia
Abstract. Understanding streamflow dynamics at the catchment scale remains an arduous task; this is especially true for non-perennial networks. While modelling tools offer important advantages to study streamflow dynamics, the highly nonlinear, unsaturated dynamics associated with the transitions between wetting and drying in non-perennial systems make modelling cumbersome. This has stifled previous modelling attempts and alludes to why there is still a knowledge gap. In this study, we first construct a conceptual model of the physical processes of streamflow generation in an intermittent river system in South Australia, based on the hypothesis that the vertical and longitudinal soil heterogeneity and topography in a basin control short-term (fast flows), seasonal (slow flow), and a mixture of these two. We then construct and parameterise a fully integrated surface-subsurface hydrologic model to examine patterns and mechanisms of streamflow generation within the catchment. A set of scenarios are explored to understand the influences of topography and soil heterogeneity across the catchment. The results showed distinct flow generation mechanisms develop in the three conceptualized areas with marked soil and topographic characteristics, and suggested that capturing the overall distribution of soil types across the catchment was more important than capturing the wide variability of soil hydraulic properties. This study augments our understanding of catchment scale streamflow generation processes, while also providing insight on the challenges of implementing physically-based, integrated surface-subsurface hydrological models in non-perennial stream catchments.
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Karina Y. Gutierrez-Jurado et al.
Status: final response (author comments only)
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RC1: 'Comment on hess-2020-659', Anonymous Referee #1, 23 Feb 2021
General comments
This study is a follow-up of a 2019 research paper by Gutierrez-Jurado et al. where an integrated surface-subsurface hydrological model (ISSHM) was applied to explore the processes that lead to the transition from a dry streambed to a flowing stream in non-perennial streams. Here an adapted version of this ISSHM was applied to the Pedler creek catchment. The authors consider different streamflow generating mechanisms for three catchment areas based on the catchment topography and six detailed soil profiles. They use Hydrogeosphere to simulate a set of eight scenarios (3 of these are discarded because of high computation times) with different hydraulic conductivity parameters and an (un)incised river network. The results show that different flow generating mechanisms ensue in different catchment areas, based on the soil properties (or topography).
I strongly recommend for the authors to improve the readability of their manuscript. The sometimes odd sentences make it hard for the reader to grasp the content.
Specific comments
The introduction needs to be thoroughly revised (see technical corrections). It would be interesting to include a compact review of past modeling efforts of non-perennial rivers as in l40 the authors touch on that only briefly. Also, in the paragraph on using numerical models for this purpose (l39-l50), the dis(advantages) of such models can be more broadly addressed. Although the goal of the study is mentioned, a hypothesis or research question is missing here and should be specified.
In Sections 2.2.1 to 2.2.3 the authors state the most dominant streamflow generating processes for the different topographical areas they consider. It is unclear however where these hypothesis originate from as no references to existing literature are made.
If I understand the modeling setup correctly, different hydraulic conductivity parameters were chosen for sand and loam. The authors should mention clearly how these parameters were obtained and what parts of the model were calibrated. Also, I’m questioning the suitability of using a numerical model to look at the impact of subsurface hydraulics to stream flow generation, as the authors indicate in the discussion (l422-424) a conceptual model might be a better fit.
Technical corrections
See attachment
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AC1: 'Reply on RC1 and RC2', Margaret Shanafield, 12 Apr 2021
We thank the two anonymous referees for their considerate and comprehensive comments. We are glad to see that both reviewers are broadly supportive of this manuscript and had no fundamental issues with the methodology or results.
Referee 1 has provided extensive edits to improve the readability of the manuscript. We appreciate the they have taken to not just suggest revision of the text, but to be specific in how to make this improvement. Given this level of detail, it should be no problem to meet the referee’s request. Moreover, we are happy to reformulate the objective as a research question, to add the requested background on parameter selection and model setup, and to include more lengthy discussion of how these results are useful in other catchments with different geology.
Finally, both referees noted that the use of a numerical model in unsaturated, very transient conditions along a stream network is not trivial; however, we seek to understand and separate the contributions of various physical processes in generating and sustaining this periodic flow; as explained in the introduction, separating these physical processes requires a process-based, integrated model. We will add more background detailing the past use of numerical models for understanding streamflow generation, so that the logical progression of complexity that led to this modelling effort is clearer.
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AC1: 'Reply on RC1 and RC2', Margaret Shanafield, 12 Apr 2021
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RC2: 'Comment on hess-2020-659', Anonymous Referee #2, 18 Mar 2021
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AC2: 'Reply on RC1 and RC2', Margaret Shanafield, 12 Apr 2021
We thank the two anonymous referees for their considerate and comprehensive comments. We are glad to see that both reviewers are broadly supportive of this manuscript and had no fundamental issues with the methodology or results.
Referee 1 has provided extensive edits to improve the readability of the manuscript. We appreciate the they have taken to not just suggest revision of the text, but to be specific in how to make this improvement. Given this level of detail, it should be no problem to meet the referee’s request. Moreover, we are happy to reformulate the objective as a research question, to add the requested background on parameter selection and model setup, and to include more lengthy discussion of how these results are useful in other catchments with different geology.
Finally, both referees noted that the use of a numerical model in unsaturated, very transient conditions along a stream network is not trivial; however, we seek to understand and separate the contributions of various physical processes in generating and sustaining this periodic flow; as explained in the introduction, separating these physical processes requires a process-based, integrated model. We will add more background detailing the past use of numerical models for understanding streamflow generation, so that the logical progression of complexity that led to this modelling effort is clearer.
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AC2: 'Reply on RC1 and RC2', Margaret Shanafield, 12 Apr 2021
Karina Y. Gutierrez-Jurado et al.
Karina Y. Gutierrez-Jurado et al.
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