| 02 Jan 2026
Citizen science as a long-term environmental baseline: assessing impacts of a small dam removal in Montana, USA
Abstract. As dam removals increase in frequency across the U.S., most research has focused on the impact of larger dam removals, despite the removal of small dams being much more common. There are hundreds of small dams in Montana, and this research investigates impact on stream ecology and morphology using citizen science data collected over eight years spanning before and after a 2020 small dam removal in Rattlesnake Creek. We analyzed pebble count grain size distributions and aquatic macroinvertebrate biotic indices from 2017 to 2024 to assess changes in sediment transport and macroinvertebrate population as well as evaluate the efficacy of citizen science for long-term stream monitoring. Our analysis includes comparisons of pre– and post–dam removal data collected from above and below the dam site. Our findings revealed no significant changes in grain size or macroinvertebrate index values between upstream and downstream reaches post–dam removal, suggesting that the removal of this small dam had minimal detectable impact on sediment transport and macroinvertebrate communities within the study period. Our study also demonstrates the capacity for citizen science programs to effectively collect robust and valuable datasets. This study underscores the importance of meticulous data management along with the potential for, and challenges of, citizen science for environmental research. We provide recommendations for "best practices" to improve future citizen science monitoring and informing decision-making for future dam removals, particularly for the nine dams further upstream within the Rattlesnake Creek watershed.
The focus of this manuscript is to explore the effectiveness of working with citizen scientists to collect long-term environmental data with support from a project team, specifically focused on the impact of a small dam removal. In its current form, the manuscript does not clearly align with the stated aims and scope of the journal, it would be more appropriate elsewhere, or requires substantial reworking with major revisions at least.
Below are line-by-line comments with further points that I hope that the authors find constructive.
L27 "Both species" - what species are you referring to?
L36 There are nine dams in the abstract, why are there now seven?
L53 "Local streams" - what are the size of these and location relevant to where the citizens are coming from?
L60 By "above-dam levels" do you mean upstream of the dam?
L66 What about research outside of the US? Such as in central Europe on check dam removal?
L78 9177 m is higher than Everest! Assume there is a typo here.
L88 Consider adding this information regarding the stream gauge to the Figure 1, alongside the actual data for the monitoring period as this will provide useful context for the rest of the manuscript.
L94 Seven dams again - please clarify whether this is correct or not and update the abstract accordingly.
L105-114 "This paragraph is a little confusing and needs restructuring. At the moment, it is presented as: "citizen science is good for spatiotemporal scales, yet data quality is potentially not robust. Research has found it to be non robust enough, but this is like comparing apples to oranges, so citizen science data is robust."
I think this needs unpicking more as you can compare citizen science data to that collected as standard, by using the standard data as a reference point. While citizen science has demonstrated value in many contexts, it is important to clearly articulate where it is appropriate and where limitations exist.
L125 How were these hours distributed across the study period? Were they equal, or did more monitoring occur in 2018, for example. How did this effect your results? How many people were engaged and how many were the same over the monitoring period?
L126-144 This information should all come in further up in my opinion when you are introducing the study site. This would then leave a dedicated section to discuss the citizen science objectives/protocol.
L157 This sentence doesn't make sense, please clarify/revise.
L162-163 How were these sites identified? Why only two upstream but eight downstream?
L171 More information is required regarding the width of the streams at the 10 monitoring sites, and why 20-50 intervals were chosen. Did you normalise the stream widths?
L230 "Winter season WEN" - this suggests that volunteers had different roles, please expand on this.
L230 Can you share the Excel sheet so that others with similar objectives can learn from your design?
L269-271 Why use the upstream sites as comparisons when you have three years of data before dam removal? This is the point of BACI. Furthermore, there might be changes upstream due to flow being no longer restricted.
L273-274 What about the data before/after then as this would give greater detail into how the river responded to the dam removal?
L275 How many observations? More detail required
L279 Why did you only calculate d50? If there are 100 measurements per sample site why not include the entire grain size distribution, including d16, d50 and d84 as stated in the methods?
L285 Figure 2 - I think that these figures would be better combined, showing the change throughout time based on the year. It is unclear where the error bars have originated from, why not use a percentile metric to calculate the 95% confidence intervals? See Eaton et al., 2019, ESurf, https://doi.org/10.5194/esurf-7-789-2019 for example.
L289 Figure 3 - similar comment to Figure 2, I don't think separating the data in this way is additive, therefore please think about combining the plots. Also it's unclear how the error bars were calculated.
L293-299 This paragraph would benefit from reframing, as it reads as if the citizen science data were effective in their collection, however a third of the data collected was not usable. Please consider how this is framed.
L301-305 This is not discussion as it doesn't link to the presented results as there was no significant change.
L307 "sediment flow" - you have not reported measuring sediment flow, rather grain size distributions and WAV. Please reword.
L308-312 This is results rather than discussion, why isn't this presented earlier in the results section? It contains important information that has not been presented.
L312 What irregular variation? More information is required.
L319-324 This is introduction to the area rather than discussion. Equally for the sluice gate statement, this should come earlier in the text.
L329-334 This is not discussion, it is introduction. Secondly, the results presented don't back up these claims as there's no evidence to support them. It's also not what the focus of the manuscript currently is. If you have anecdotal stories/evidence that would be more effective.
L336-339 Again this is introduction, not discussion.
L341-350 This raises a quality control issue that has not been addressed - why was all of this potentially fantastic data not quality controlled or checked regularly?