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: open (until 27 Mar 2021)
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RC1: 'Comment on hess-2020-659', Anonymous Referee #1, 23 Feb 2021
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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
Karina Y. Gutierrez-Jurado et al.
Karina Y. Gutierrez-Jurado et al.
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