Examination of an Electrified Bar Rack Fish Guidance Device for Hydropower Turbines

Round 1

Reviewer 1 Report

In this interesting work, the authors investigated the potential of the “Center Sender” in reducing mortality caused by the passage of fish in the hydroelectric turbines. The authors propose that the device is mounted within the intake of a turbine, guiding  downstream-passing fish towards the center of the turbine where blade velocities are lower and  blades are thicker, likely reducing the potential for fish to be injured.

The manuscript has quality to be published. I believe, however, that there are some aspects that can be improved and that I indicate below:

Line 68 to 70 – This text seems more appropriate for the “Materials and Methods” chapter

Line 150 - the characterization of the electrical stimulus must include the amperage

Line 156 - What is the main reason for using this species. The biological and ecological aspects of the species relevant to the experience should be identified (life cycle, migrations, spawning, etc.)

Line 200 - Make it clear if the fish were not used in more than one test

Line 354 – (Discussion) The discussion consists mainly in reinforcing  arguments favorable to the system. The constraints regarding aspects related to the downstream migrations of the fish selected for the tests, such as season of the year, day/night period, water temperature, should be more evident. Differences in fish size in electric field effects are well identified in the text.

Author Response

Line 68 to 70 – This text seems more appropriate for the “Materials and Methods” chapter 

This is describing a similar, previously used electrical barrier and therefore we believe that this is suitable to remain in the introduction as this is a statement of prior research.  

Line 150 - the characterization of the electrical stimulus must include the amperage 

Amperage was added: The necessary amperage need for fish guidance depends on several factors including the used voltage, surface area of electrodes, number of electrodes, conductivity of the water etc. In the performed experiments, the maximum amperage varied between 35-40 mA. 

Line 156 - What is the main reason for using this species. The biological and ecological aspects of the species relevant to the experience should be identified (life cycle, migrations, spawning, etc.) 

Added the following sentences: Rainbow trout were selected for our study for several reasons including their representation of salmonids which many populations are threatened and migrate making them susceptible to encountering hydropower facilities and other water infrastructure. Additionally, rainbow trout are easily obtainable and have been extensively studied in previous research. 

Line 200 - Make it clear if the fish were not used in more than one test 

Edited text to the following: After the 48 hour evaluation, the fish were euthanized. Each fish was an independent sample and was not used in additional trials. 

Line 354 – (Discussion) The discussion consists mainly in reinforcing arguments favorable to the system. The constraints regarding aspects related to the downstream migrations of the fish selected for the tests, such as season of the year, day/night period, water temperature, should be more evident. Differences in fish size in electric field effects are well identified in the text. 

Added: and may also be influenced by water temperature, water chemistry, and time of day or season. 

Reviewer 2 Report

Water – 2354955 Examination of electrified bar track rack guidance device for turbines

This manuscript is the best well-written manuscript I have reviewed in quite some time. I just have a few suggestions later in this review. The intent is clear, the methodology seems good, the results are clear, and the discussion is relatively straightforward. I recommend it be published with minor revisions.

11.     Line 244. I did not see ADV prior to this line, so please write out here (with ADV in parentheses afterwards).

2.2     Table 6. Why did you use so many fish for scenario 1 (n = 70) and the other Bar = none (n = 80)? Was this explained? Only one rate of passage approach was quite weak (2.3%), which occurred at 0.4 m/s. The only other one in this 0.4 grouping with a lost percentage was 25.4% and 20.0%. s there some way to rank-order these trials so that the best combinations appear at top, and the worst appear below? It is not easy to pick out the trends.

33.     In Table 6, it appears that trial information was combined. I would be nice to have a “mean number of approaches per fish” plus or minus the SD, and number of passages per trial for that combination. There is no way to determine variability.

44.     Figure 4. The grey bars are difficult to see. Outline both grey and pink bars. The X axis is “Flume lane number”.  The text should say, “Number of fish?” or “Number of attempts”? of fish.  Not clear. How many trials per each histogram? I think it would be better if grey and pink bars were all on the Y axis, and maybe showing those that are significantly different marking them from results of a rank-order test?

55.     Same issues with Figure 5.

66.     I did not see any mention of an Animal Care and Use protocol approved by the funding agency or the university. There was no description of a protocol with the exception of a bucket, net, and 2 week holding time.

Author Response

Water – 2354955 Examination of electrified bar track rack guidance device for turbines

This manuscript is the best well-written manuscript I have reviewed in quite some time. I just have a few suggestions later in this review. The intent is clear, the methodology seems good, the results are clear, and the discussion is relatively straightforward. I recommend it be published with minor revisions.

11. Line 244. I did not see ADV prior to this line, so please write out here (with ADV in parentheses afterwards).

ADV is defined in line 119

“The actual velocity distribution in the reduced flume section at the two operating velocities was measured with acoustic doppler velocimetry (ADV) using a SonTek FlowTracker2 handheld Acoustic Doppler Velocimeter.”

2.2     Table 6. Why did you use so many fish for scenario 1 (n = 70) and the other Bar = none (n = 80)? Was this explained? Only one rate of passage approach was quite weak (2.3%), which occurred at 0.4 m/s. The only other one in this 0.4 grouping with a lost percentage was 25.4% and 20.0%. Is there some way to rank-order these trials so that the best combinations appear at top, and the worst appear below? It is not easy to pick out the trends.

The 2 scenarios conducted without bars installed were regarded as controls and were used to conduct an additional analysis of behavior between days which required additional samples. The additional trials also provided control tests distributed throughout testing to help ensure any conflicting variables might be identified.  Results were presented in a logical order based on the experimental variables and the authors prefer to have it remain this way and allow the figures to highlight the trends.

33. In Table 6, it appears that trial information was combined. I would be nice to have a “mean number of approaches per fish” plus or minus the SD, and number of passages per trial for that combination. There is no way to determine variability.

Because fish were not individually identified, and some fish were able to pass multiple times, we were only able to quantify approaches at trial level therefore SE would be based a trial level which for most tests was only 2 trials, therefore it would not be appropriate to report SE in this case.

33. Figure 4. The grey bars are difficult to see. Outline both grey and pink bars. The X axis is “Flume lane number”.  The text should say, “Number of fish?” or “Number of attempts”? of fish.  Not clear. How many trials per each histogram? I think it would be better if grey and pink bars were all on the Y axis, and maybe showing those that are significantly different marking them from results of a rank-order test?

This appears to have been an issue with the version received or if printed the printer? We are happy to work with the editors to ensure these images are suitable for the production version.

55. Same issues with Figure 5.

                  Same response as for Figure 4

66. I did not see any mention of an Animal Care and Use protocol approved by the funding agency or the university. There was no description of a protocol with the exception of a bucket, net, and 2 week holding time.

This is located at the end of the document in the Institutional Review Board Statement

Reviewer 3 Report

General comments

-          The article is a very well-presented research article from a relevant and important research field. To avoid fish in hydropower is a prerequisite for continuation of hydropower operation and development.

-          The objective, the research itself, and the findings are clear and cannot be misunderstood. The conclusions are convincing, both from the findings in the research and from similar experience from other sites.

-          Some statistical analysis can be presented in a shorter way, it’s mainly interesting for those interested in statistical analysis. Please see if it can be reduced and please avoid duplicated information.

-          The use of numbers or text for number <10 is inconsequent in the article. Please do a revision through the article, use of text (one-two-three-four-…..) is preferable for number <10.

-          The article should be published after minor review.

 

Detailed comments

12           There are several places in the article presented ‘turbine’ as a general item. Pelton, Francis, Kaplan, Turgo, Crossflow, Bulb turbines, Propellers, are all turbines. It is not found in the article which kind of turbine this research is developed for. I guess the authors may have the Kaplan turbine in mind when writing this (due to the ‘hub’ in line 79), but please be clear to avoid any costly and violent misunderstanding. This comment is valid several places in the text.

28           From my experience electric fish barriers are more common in outlets from hydropower than inlets. Please mention outlets in the text.

85           Water velocities in ‘turbine intakes’ are discussed. It is not clear what a ‘turbine intake’ is? Is it the intake in the river or is it the inlet to the turbine itself? Intakes in rivers are never mentioned as ‘Turbine intakes’. The velocities described (1 – 4 m/s) seems far too low to represent the velocities in the inlet of the turbine? Please make the location clear.

85           Regions upstream? What do you mean? This is not accurate.

90           A velocity of 0,4 m/s relevant for a turbine. I very much doubt on this. Velocities around 9,5 m/s are normally found in the intake in the river for rather small hydropower plants.

101         Where is the flume located? In PNN Lab in WA, USA?

101         Painted? Sounds like unnecessary information.

135         Table 1. How can you measure the diameter of a bar? Diameter is relevant for a rod, not a bar. Please replace all ‘bar’s with ‘rod’s if it is rods you have used in the experiment. I agree that bars are more commonly used in racks for hydropower, but please be accurate here.

157         Here, Rainbow trout are measured and reported with mm accuracy, with three digits. This is not relevant, neither possible. The mean value is even presented with four digits. This is not possible for live species and this will differ from the way you are doing the measurements. I think the numbers should be reduced to two digits, specially the mean value.

160         Here, 300 gallon (one digit) seems to be converted to 1136 l (four digits)? This is serious misleading.  Please be consistent to the accuracy.

168         Temperatures like 12 – 13⁰C? What do they represent? Winter or summer conditions. Are the temperatures relevant for the migration studied? Please give a brief description?

180         Here a new notation appears; [m s-1]? Please use the [m/s] used earlier in the article and please be consistent. The notation m/s is most relevant for applied science.

186         Please specify early in the text whether each fish is used only once? It seems to be like that later in the article but please specify.

195         Dipnet? I am not familiar with this phrase, please describe.

195         Too many spaces.

200         Is the fish released back to the river or are they sent one more turn into the experiment? Or eaten?

216         In Figure 3 the photos are in different scale, which make direct comparison confusing. There is a yellow dotted line outside the photos and even between the photos. What does this mean?

235         With module angle 0^o, does it mean that the module is placed in longitudinal direction with the flume close to the sidewall? From Table 6 it may be understood that there are no bars?

239         F-tests are just known to those who know what a F-test is?

248         Please include [m/s] as the unit somewhere in the Table.

262         Table 6. The column ‘Bar Incline Angle’? Is 0^o equal to N/A?

262         The codes used in the column ‘Bars’ is not known or found elsewhere. T&B? Top and bottom? I am just guessing.

300         It is appreciated that the authors are honest on reporting fish which are moving upstream in the flume. This disturbs the statistics a lot. It is proven before that fish learn very quickly and fish going through the system twice or more will not be representative for ‘natural’ fish coming through the system.

316         A velocity is not slow, it is low. Incl line 319.

327         The information in Table 8 and Figure 7/8 is more a proof than useful information. Could this be given in a more ‘interesting’ way. Or deleted? Or just described?

360         Why is this information useful just for ‘Turbine intakes’? Why not ordinary intakes? I can’t see this.

376         This ‘Turbine intake’ things sound still weird? Yes, water velocity in a turbine is much higher than 0,4 m/s.

389         Still exclusive for Turbine intakes?

None

Author Response

General comments

-          The article is a very well-presented research article from a relevant and important research field. To avoid fish in hydropower is a prerequisite for continuation of hydropower operation and development.

-          The objective, the research itself, and the findings are clear and cannot be misunderstood. The conclusions are convincing, both from the findings in the research and from similar experience from other sites.

-          Some statistical analysis can be presented in a shorter way, it’s mainly interesting for those interested in statistical analysis. Please see if it can be reduced and please avoid duplicated information.

-          The use of numbers or text for number <10 is inconsequent in the article. Please do a revision through the article, use of text (one-two-three-four-…..) is preferable for number <10.

-          The article should be published after minor review.

Detailed comments

12         There are several places in the article presented ‘turbine’ as a general item. Pelton, Francis, Kaplan, Turgo, Crossflow, Bulb turbines, Propellers, are all turbines. It is not found in the article which kind of turbine this research is developed for. I guess the authors may have the Kaplan turbine in mind when writing this (due to the ‘hub’ in line 79), but please be clear to avoid any costly and violent misunderstanding. This comment is valid several places in the text.

Turbine is presented as a general because the tested device has the potential to beneficial to many turbine types. The text was edited to clarify that propeller type turbines might be the most applicable.

28           From my experience electric fish barriers are more common in outlets from hydropower than inlets. Please mention outlets in the text.

Added: The application of electricity has mostly been used as a deterrent, forming behavioral barriers to keep invasive fish species out of certain areas such as hydropower outlets [10,13,14].

85           Water velocities in ‘turbine intakes’ are discussed. It is not clear what a ‘turbine intake’ is? Is it the intake in the river or is it the inlet to the turbine itself? Intakes in rivers are never mentioned as ‘Turbine intakes’. The velocities described (1 – 4 m/s) seems far too low to represent the velocities in the inlet of the turbine? Please make the location clear.

The intake to a hydropower facility is a common term used in the field of hydropower and understood by those familiar with the industry. The intake refers to the structure or opening in the dam or reservoir that allows water to flow into the turbine where the energy is extracted from the water to generate electricity. After the turbine intake, the water flows through a penstock (which I assume the commenter is reffering to when mentioning the turbine inlet), which is a large pipe that carries the water from the intake to the turbine. Water velocities in the penstock will almost always exceed the velocity in the intake.

We believe that these terms are widely understood in the field of hydropower and find it unnecessary to further define in the text beyond what was originally written, though we will defer to the editor’s suggestions if these further details are needed.

To clarify regions upstream, (i.e., reservoir, headwaters, etc.) was following the use of the term.

85           Regions upstream? What do you mean? This is not accurate.

          Changed to: regions further upstream (i.e., reservoir, headwaters, etc.),

90           A velocity of 0,4 m/s relevant for a turbine. I very much doubt on this. Velocities around 9,5 m/s are normally found in the intake in the river for rather small hydropower plants.

Edited to specify as a generality: Turbine intakes have substantially higher velocities (generally between 1 and 4 m s^-1)

101         Where is the flume located? In PNN Lab in WA, USA?

Added: The test flume was built at the Natel Energy facility in Alameda, California.

101         Painted? Sounds like unnecessary information.

Painted was removed

135         Table 1. How can you measure the diameter of a bar? Diameter is relevant for a rod, not a bar. Please replace all ‘bar’s with ‘rod’s if it is rods you have used in the experiment. I agree that bars are more commonly used in racks for hydropower, but please be accurate here.

Stainless steel round bar was used, which seems to be used interchangeably with rod in many cases.

157         Here, Rainbow trout are measured and reported with mm accuracy, with three digits. This is not relevant, neither possible. The mean value is even presented with four digits. This is not possible for live species and this will differ from the way you are doing the measurements. I think the numbers should be reduced to two digits, specially the mean value.

Fish were anesthetized and it was possible to measure to mm accuracy. – removed decimal from mean.

160         Here, 300 gallon (one digit) seems to be converted to 1136 l (four digits)? This is serious misleading.  Please be consistent to the accuracy.

The conversion was conducted using a conversion factor of 3.785 l per gal. That is why 4 digits are used. We think it would be more misleading to say that the tank is 1000 liters which does not account for 136 liters.

168         Temperatures like 12 – 13⁰C? What do they represent? Winter or summer conditions. Are the temperatures relevant for the migration studied? Please give a brief description?

Added: “During testing, temperatures within the flume were on average 13.0 °C and averaged 12.2 °C within the holding tanks, representative of summer river conditions for rainbow trout native habitat (Table 2). Water conductivity within the flume ranged from 201 to 320 µs cm-1 during testing, representing a common range observed in freshwater rivers within the United States [30]. “

180         Here a new notation appears; [m s-1]? Please use the [m/s] used earlier in the article and please be consistent. The notation m/s is most relevant for applied science.

Changed all to m s-1

186         Please specify early in the text whether each fish is used only once? It seems to be like that later in the article but please specify.

Added: “Each fish was an independent sample and was not used in additional trials.”

195         Dipnet? I am not familiar with this phrase, please describe.

Dipnet is a standard term and commonly used in fisheries and aquatic research.

195         Too many spaces.

Fixed

200         Is the fish released back to the river or are they sent one more turn into the experiment? Or eaten?

Added: ‘After the 48 hour evaluation, the fish were euthanized.’

216         In Figure 3 the photos are in different scale, which make direct comparison confusing. There is a yellow dotted line outside the photos and even between the photos. What does this mean?

Figure was updated to address these concerns.

235         With module angle 0^o, does it mean that the module is placed in longitudinal direction with the flume close to the sidewall? From Table 6 it may be understood that there are no bars?

0° was changed to N/A which is considered the control test.

239         F-tests are just known to those who know what a F-test is?

F-test is a standard statistical test

248         Please include [m/s] as the unit somewhere in the Table.

0.4 m/s is in the heading row

262         Table 6. The column ‘Bar Incline Angle’? Is 0^o equal to N/A?

Changed to N/A

262         The codes used in the column ‘Bars’ is not known or found elsewhere. T&B? Top and bottom? I am just guessing.

Text was added to clarify this in the table caption.                                

300         It is appreciated that the authors are honest on reporting fish which are moving upstream in the flume. This disturbs the statistics a lot. It is proven before that fish learn very quickly and fish going through the system twice or more will not be representative for ‘natural’ fish coming through the system.

         Agreed, though it is not clear if this needs to be further explained.

316         A velocity is not slow, it is low. Incl line 319.

Added: “At the lower velocity...”

327         The information in Table 8 and Figure 7/8 is more a proof than useful information. Could this be given in a more ‘interesting’ way. Or deleted? Or just described?

The authors belive that table 8 and and figures 7 & 8 are necessary to convey the variables that influence lane movement and the trends that were observed for each.

360         Why is this information useful just for ‘Turbine intakes’? Why not ordinary intakes? I can’t see this.

Added: or within other water infrastructure

376         This ‘Turbine intake’ things sound still weird? Yes, water velocity in a turbine is much higher than 0,4 m/s.

Addressed in previous comment.

389         Still exclusive for Turbine intakes?

Added: and other water infrastructure

Reviewer 4 Report

This manuscript is a worthy contribution to the field – mortality in fishes migrating through turbines is a pertinent issue, and the new technology tested here (electrifying the infrastructure) is interesting. The experimental approach used is valid; the statistical analysis is fine (but see below – it would benefit with a bit of restructuring), and the manuscript is well written. There are two small issues:

1) The presentation of the statistics could be slightly improved

·       L221-231. The Methods section presents Shapiro-Wilk, Levene and Mann-Whitney-Wilcoxon tests, but these are not reported in the Results. Additionally, I couldn’t find any text before this referring to the experiment day, so these tests for the effect of day don’t seem to have any context. Can the authors include the experiment dates?

·       L279: I suggest changing to “the difference between passage lane and entrance lane (i.e. lane movement)…” That is, insert “lane movement” to set up the next paragraph.

·       L291: The authors use the term “ANCOVA”. The first model they present (results shown in Figure 6) looks like it only uses categorical variables as predictors, so surely it is not an ANCOVA? Maybe they could just use the term “linear model” for both models?

·       The authors present 2 models (that shown in Figure 6, where they do not include approach lane; and that shown in Figure 7 and 8, where they include approach lane). Can this be stated more explicitly in the Methods? In particular, L303-312, describing the modelling approach where lane is included, could be moved to the Methods.

2) The authors are describing a new and complex experimental layout. This would actually benefit from a photo – it’s a bit difficult to visualize this from the description alone. Note: it is not necessary to do this – this is just a suggestion. Also, if I am not mistaken, the ADV measurements in Figure 1, are shown by gray squares, not “x” symbols; this should be changed in the caption.

Author Response

1) The presentation of the statistics could be slightly improved 

Edits were completed for the statistics following the specific suggestions below.

 L221-231. The Methods section presents Shapiro-Wilk, Levene and Mann-Whitney-Wilcoxon tests, but these are not reported in the Results. Additionally, I couldn’t find any text before this referring to the experiment day, so these tests for the effect of day don’t seem to have any context. Can the authors include the experiment dates? 

Added the following to the results: Passage positions of control fish were not normally distributed on 3 of 4 days (not sure if you want to present P-values here but for the 3 that deviated from normality Shapiro-Wilk P<=0.032 and for the 1 that was normal S-W P = 0.185). Variances were not homogeneous (Levene’s P=0.017). Passage positions were similar (Welch’s P = 0.154). 

L279: I suggest changing to “the difference between passage lane and entrance lane (i.e. lane movement)…” That is, insert “lane movement” to set up the next paragraph.

Added: (i.e., lane movement) 

L291: The authors use the term “ANCOVA”. The first model they present (results shown in Figure 6) looks like it only uses categorical variables as predictors, so surely it is not an ANCOVA? Maybe they could just use the term “linear model” for both models?

Analysis of covariance is a combination of an ANOVA and a regression analysis. It is a method for comparing sets of data that consist of a treatment (velocity, angle, bars, voltage) and an effect (lane movement) when a third variable (entrance lane [the covariate]) exists that can be measured but not controlled that has an effect on the variable of interest (lane movement).  

The authors present 2 models (that shown in Figure 6, where they do not include approach lane; and that shown in Figure 7 and 8, where they include approach lane). Can this be stated more explicitly in the Methods? In particular, L303-312, describing the modelling approach where lane is included, could be moved to the Methods.

The approach lane is included as the x-axis in figures 6, 7, & 8.  

2) The authors are describing a new and complex experimental layout. This would actually benefit from a photo – it’s a bit difficult to visualize this from the description alone. Note: it is not necessary to do this – this is just a suggestion. Also, if I am not mistaken, the ADV measurements in Figure 1, are shown by gray squares, not “x” symbols; this should be changed in the caption. 

The ADV measurements are denoted by an encircled “x” however depending on the resolution they can look like gray squares. Authors are happy work with the journal to ensure this is clear in the final version of the article.