Balancing Physical Channel Stability and Aquatic Ecological Function through River Restoration
Round 1
Reviewer 1 Report
The manuscript presents an interesting study. The research topic is relevant. The article is well formatted. The conclusions are justified. Research methods are reliable. I am sure that the manuscript can be published.
Author Response
Thanks for the encouraging review.
Reviewer 2 Report
Manuscript ID: water-2372545
Title: Balancing physical channel stability and aquatic ecological function through river restoration.
OVERVIEW
This paper presents a sequence of modified vortex rock weirs (VRW) in a small-scale watercourse in southern Ontario, Canada, to assess the fish passage suitability and identify best practices for VRW design and construction.
GENERAL COMMENTS
The subject matter is actual, interesting and within the scope of the Journal Water.
The manuscript complies with the journal template.
The title is adequate.
The English spelling and grammar are fine.
The manuscript is original, and plagiarism was not detected.
The objectives are clearly stated.
The manuscript provides information on its replicability and reproducibility.
The analyses are appropriate and well-described.
The tables and figures are fine.
The interpretation and results are supported by the data.
The conclusions report the major findings of the study.
The strengths and limitations of the study are reported.
The manuscript structure, flow and writing are fine.
The manuscript addresses a well-known problem but provides detailed information for the application of bibliographic data to a real-world case study.
In conclusion, I believe this manuscript is interesting and worthy of publication as it is.
Author Response
Thanks for your review.
Reviewer 3 Report
In this research, the authors investigate how the design and construction of vortex rock weirs (VRWs) can be modified (in terms of gradient, width, keystone-size, and pool-length) to permit an optimum fish passage suitability and population management strategies (in terms of water level and temperature conditions, and channel geometries and stability), with an application in a watershed in southern Ontario (Canada). I much enjoyed reading this work, and in my opinion, it contains several innovations regarding the existing literature, in terms of the design components for small-bodied fish passages without risking the channel stability from the impact of the VWRs. Please see some minor comments and suggestions I have gathered while reading this interesting work:
1) It is mentioned that "During site visits, there were incidental observations of small-bodied fish species in the pools and moving upstream through the VRWs.". In these visits were any difficulties for the fish passages detected? Was any of the locations determined to be better or worst in terms of the fish passage? Were there any trap locations for fish when the depth was too low or preferred passages when the depth was high? I think it would be beneficial for the readers to share (maybe in an appendix) the experience from these visits to highlight the necessity of in-field research before suggesting any design criteria.
2) It is mentioned that "over 530 velocity measurements were collected to identify the range of velocities at each pool feature". Please specify whether the surface velocity was recorded or the whole velocity vertical profile and at what location related to the VWRs location (this also plays role in the determination of the river discharge estimated from the weir empirical expressions or from the surface velocity; e.g., see discussion in a recent work by Koussis et al., 2022). Do you think the vertical profile or the surface velocity plays a more significant role in fish passability? How do fish correspond to different velocity profiles?
, Discharge estimation from surface-velocity observations by a maximum-entropy based method, Hydrological Sciences Journal, 67:3, 451-461, 2022.
3) In this work, it seems that only the mean velocity plays an important role to the fish passages. Do you think that also turbulence (e.g., variability of the water velocity and depth) due to the VRW and energy dissipation would have any impact on the fish passages (e.g., see discussion in Hockley et al., 2014)?
Hockley, F. A., Wilson, C. A. M., Brew, A., & Cable, J. (2014). Fish responses to flow velocity and turbulence in relation to size, sex and parasite load. Journal of the Royal Society Interface, 11(91). https://doi.org/10.1098/rsif.2013.0814
4) The investigation is more focused on fish passability under low, intermediate, and high water level conditions; how about showing the results with low, intermediate, and high velocities (e.g., see Fuentes et al., 2021)? Is there any connection between depth-velocity-temperature in terms of the fish passability for the specific river?
Fuentes-Pérez JF, García-Vega A, Bravo-Córdoba FJ, Sanz-Ronda FJ. A Step to Smart Fishways: An Autonomous Obstruction Detection System Using Hydraulic Modeling and Sensor Networks. Sensors. 2021; 21(20):6909. https://doi.org/10.3390/s21206909
5) Regarding the conclusions of this study, can they be applied in other rivers/locations? What are the characteristics that need to be similar in other rivers/locations for the proposed practices to be applied, for example, similar channel geometrical characteristics such as width and depth, etc.? Please see a similar study for the design of obstacles to assist fish passability by Miranda et al. (2021).
Miranda FC, Cassan L, Laurens P, Tran TD. Study of a Rock-Ramp Fish Pass with Staggered Emergent Square Obstacles. Water. 2021; 13(9):1175. https://doi.org/10.3390/w13091175
6) If possible, it would be very interesting to discuss how fish would correspond not only to water temperature and depth absolute values but also to their seasonality (i.e., change between seasons or even during the day), and any strong trends or high long-term variability (which is a common phenomenon in all key hydrological-cycle processes such as temperature, water depth and discharge; e.g., see discussion in a global-scale analysis by Dimitriadis et al., 2021). Is there any work in the literature dealing with this issue?
Dimitriadis, P., D. Koutsoyiannis, T. Iliopoulou, and P. Papanicolaou, A global-scale investigation of stochastic similarities in marginal distribution and dependence structure of key hydrological-cycle processes, Hydrology, 8 (2), 59, doi:10.3390/hydrology8020059, 2021.
Author Response
Thank you for the thought-provoking and detailed review, it is much appreciated.
Below is our response, our number correspond to the numbered points in the review:
1 - We have added a short description of fish observations into Supplementary Material (referenced in the text at line 144) as suggested by the reviewer. We did not use traps, and we did not physically handle fish to assess potential health. We did not observe any physical distress.
2 - Velocity was measured at 60% of the total depth (line 109-118) in the pools at the cross-sections identified in Fig 4. As we do not have a full velocity profile, we are not able to address this question/comment.
3 - No doubt turbulence is important, but we do not have data to discuss this. The geometries are small (gap widths ~less than 10 cm) it is challenging to get the ADV into these spaces. We’ve kept our discussion to mean velocity as this is responsible use of the data in hand. Based on underwater camera footage and incidental observations of small-bodied fish species in Weslie Creek, and the presence of fish near in-stream vegetation and rock/boulder clusters (similar to Hockley et al., 2014 findings), it is assumed that turbulence does play an important role in fish passage, we do not have data to support a more in-depth discussion. For sure something to consider for future work.
4 - This is an interesting point. Given the size of the VRW flow pathways (particularly gaps) in Weslie Creek, it would be challenging to understand depth-velocity-temperature connections using in-situ equipment (e.g., ADV). This is an interesting concept but may be more appropriate for larger river systems or as a modelling exercise with in-field verification at suitably sized flow pathways.
5 - It is anticipated that the key design parameters in this study could be scaled up or down to be applied in other rivers/locations, as described and discussed in section 5.1 of our article. For example, varying keystone shapes and sizes must be hydraulically sound to withstand target flows in the subject river. Further, the number of keystones spanning the cross-sectional width is variable and shall be determined based on the width of the subject river. One important consideration may be the slope of the subject river – where an increased VRW gradient may not be feasible for rivers with already gentle slopes.
In terms of the study completed by Miranda et al., 2021, the uniform and square obstacles are less representative of the fishways constructed in a nature-like manner to increase fish attraction. However, combining keystones (with varying shapes and sizes) with square obstacles (made of natural and porous materials, as shown in Miranda et al., 2021), may increase complexity and fish passage suitability through VRWs on a large scale. In small river systems, such as Weslie Creek, there is the risk that additional porous materials in the VRW may result in clogging orifices and thereby reducing potential flow pathways for small-bodied fish species.
6 - In recent research conducted by Romao et al., 2018, the fish passage performance of a potamodromous cyprinid was evaluated during spring and fall (reproductive vs non-reproductive seasons) to understand whether fish passability studies yield different results depending on seasonality. In terms of fish passability, no significant differences were detected, and it was determined that for potamodromous cyprinids in particular, the evaluation of fish passage performance does not need to be restricted to a particular season. Despite these results, it was recommended that the operational regime of fishways should follow biologically meaningful seasons in a year, and the physiological state of target species should be considered.
Specific to small-scale river systems (e.g., Weslie Creek), VRWs should be constructed to allow for fish passage under high water level conditions (during the spring and fall), as well as low water level conditions (most frequent, and during the summer) to account for all life stages. By following the key design parameters outlined in this study, and ensuring complexity through the VRWs, different flow pathways (orifice, gap, and over-weir) are activated based on these seasonal water level conditions.
Romão, F.; Santos, J.M.; Katopodis, C.; Pinheiro, A.N.; Branco, P. How Does Season Affect Passage Performance and Fatigue of Potamodromous Cyprinids? An Experimental Approach in a Vertical Slot Fishway. Water 2018, 10, 395. https://doi.org/10.3390/w10040395
