Overview of the (Smart) Stormwater Management around the Baltic Sea

Round 1

Reviewer 1 Report (Previous Reviewer 1)

The authors accepted the reviewer’s comments and suggestions. All the sections are somewhat reorganized, numerous sentences rewritten, new citations included, and English language and style improved…  The Abstract is rewritten, Reference section revised and extended, several paragraphs reorganized, and the figures are clear and legible. The entire manuscript sounds more serious and cogent.

Thereby, I am convinced that the revised manuscript should be accepted for publication in Waters.

Author Response

Answer: Thank you for the positive feedback, the authors did put in a lot of effort in revamping the article.

Reviewer 2 Report (New Reviewer)

see  atttached comments

Comments for author File: Comments.pdf

Author Response

Reviewer: A very long paper..but well written

Authors: The reviewer's helpful criticism is appreciated, and the authors are thankful for it.

Reviewer: Focuses on the value of measurement with almost no reference to modelling ..eg MUSIC

Answer: Modelling is a completely different domain and it was touched upon only as much as seemed necessary (e.g., the utility of measurements for improving model was occasionally brought out). In general, the authors agree that good data is necessary for both calibration and validation.

Reviewer: Design & efficiency of green stormwater treatment systems has been reviewed by others …many times

Answer: Many others have reviewed the design and efficiency of green infrastructure on multiple occasions. However, the purpose of this article was not to conduct another review of green stormwater infrastructure, but to look into the types of smart stormwater solutions that have been implemented and make a case for increasing the proportion of green infrastructure that have been augmented. There have been a few articles that do this, but we differentiated ourselves by providing a roadmap in the form of a decision support matrix.

Reviewer: Has under quoted the extensive work undertaken in Australia by Monash Uni ( Fletcher/Deletic etc….see Google Scholar web links) over the last 2 decades. No mention of Water Sensitive Cities- CRC ( https://watersensitivecities.org.au/ ) nor the WSUD book (https://www.elsevier.com/books/approaches-to-water-sensitive-urbandesign/sharma/978-0-12-812843-5)

Answer: The authors have quoted both Fletcher and Deletic in numerous places in the article (6/4). We believe that the mix of authors referenced is sufficiently balanced. The concept of WSUD is mentioned among other approaches for other parts of the world, e.g. sponge cities, nbs, etc. (lines 225-230)

Reviewer: Suggest that each treatment technology be accompanied by a graphic that shows its method of operation ( eg rain garden)

Answer: Such illustrations describing the operation of a green infrastructure have been done numerous times and are included in nearly all handbooks of such solutions. Given the scope and length of the work, the authors felt that this was an unnecessary addition.

Reviewer: Quantitative efficiency of each treatment technology should be reported in Tables…preferably in concentration ( mg/L) & load reduction ( %)

Answer: Quantitative efficiencies are reported in the referenced papers at certain circumstances and highlighted in various manuals (e.g., ref 135, 178). Previously, these values were included in the manuscript, but due to the request of other reviewers, these have been removed. Currently it is possible to see the efficiency qualitatively in the Figure 7.

Reviewer: Need to discuss the importance of load reduction vs concentration reduction on receiving water impact

Answer: The authors have not differentiated within the manuscript concentration and load reduction. Thus, adding additional discussion into the already long manuscript is deemed unnecessary.

Reviewer: Argues real time monitoring allows real time control…no example give how a treatment train could be manipulated during a runoff event. Rather monitoring allows redesign of a more effective treatment train…which is still a good outcome

Answer: The point was not to explicitly suggest a way to manipulate a treatment train, but rather to suggest that e-monitoring and control may lead to improved performance of the system. Manipulating a treatment train would require a more technical article, but as an example it was given that hydraulic retention time could be manipulated to reduce TSS and sensors could be added to control the concentration of pollutants (additional criteria).

Reviewer: Suggest paper structure follows this order

Introduction

Water Quality Standards

Sewerage & Stormwater infrastructure in the Baltic states

Contaminants of concern

Technological solutions

Water Quality monitoring methods

Application of technologies & monitoring to assess treatment train efficacy

Conclusions

Answer: The authors are grateful for the suggestion, but do not wish to once again restructure the whole work. It has already been restructured as a response to previous reviewers’ remarks.

Reviewer: Table 2…Surrogates …needs some quantitative data….ie graphical form of the relationship & R2 of the regression equation

Answer: The r2 and equations were previously included in the manuscript. However, according to the previous reviewers’ recommendations these were omitted. It was pointed out that this does not provide sufficiently valuable information in this form.

Reviewer: Needs to better argue the value of e-monitoring using EC, pH, Turbidity, DO, etc...as real time data does not result in real time control of treatment train operation

Answer: The authors agree that the data by itself does not result in real time control, however, it is the requirement upon which real time control could be set up. The text in the manuscript (before Table 2) has been ammended to emphasize this.

Reviewer: Needs to discuss the fraction of catchment needed to be allocated to treatment technologies in order to achieve desired reduction in load or concentration. Eg bioretention basins need to occupy about 2 % of urban catchment in Australia

Answer: Discussion on the catchment allocation is an interesting one, but out of the scope of the given manuscript. There exist many published articles that cover this topic.

Reviewer: Need to discuss rainfall characteristics ….eg a <= 10mm rainfall event may capture say 80% of the annual rainfall events…hence treatment technology does not need to be sized on the biggest storms to be effective

Answer: Discussion on the rainfall characteristics is an interesting one, but out of the scope of the given manuscript. There exist many published articles that cover this topic.

Reviewer: Modelling provides the ability to design a stormwater treatment train in a given climate & mixture of land uses. It allows the design to cope with the variation in antecedent soil moisture & rainfall events between years. MUSIC model is used extensively for this purpose in Australia.

Answer: Modelling is also out of the scope of the article. The importance of it has been outlined in relevant parts of the manuscript.

Reviewer: Figure 6 is a very informative Decision Tree….the weakness is sizing the treatment train…seems to rely a lot on trial & error to get the right size !

Answer: Thank you for the comment on the decision tree. The authors were  not interested in going into the technical specifics of how to size the treatment train, that could be a new article and there are plenty of materials on this out there. However, we are showing a roadmap to implementing green infrastructure at a catchment. Each stage should be carefully investigated, but preliminarily it is possible to select the suitable solutions and to brainstorm about the options of optimizing their footprint (e.g., it is possible to minimize the size of detention ponds through implementing stormwater control measures). Lots of work has been done on that, although still not too many practical examples. Another option is to try to improve water quality through increasing hydraulic retention time or monitoring parameters directly as surrogate measurements. The point is that in general a green infrastructure is built, it takes a few years to start functioning properly, then there is some periodic monitoring, but the actual performance is difficult to evaluate (and it decreases over time). At least by implementing smart solutions it is possible to control the conditions in the system, e.g., water level, flow and attempt to manipulate the water quality.

Reviewer: I think the monitoring approach is sound to assess treatment train efficacy…but it is not needed on ALL installations. Once the modelled behaviour is confirmed by measured behaviour of field installations , surely the need for extensive monitoring is removed.

Answer: The authors agree that monitoring each distributed green infrastructure is economically unfeasible, but there are places where this approach could be used. We simply provided an overview of the solutions that have been implemented to make green infrastructure smarter (even if only for one project). The placement of these smart solutions should however be considered in key locations within the catchment, where storage could be possible. Although if the sensors become cheaper it might be possible also to expand the network to some representative green infrastructures (within the catchment).

Reviewer: There is a wide selection of WSUD /LID/SUDS design publications in Australia ( eg MW and Water by Design web links ) and the UK ( eg SUDS Manual- www.ciria.org ).

Answer: In this articles the authors were not concerned with how to properly design the solution, but rather with proposing a rationale for improving existing or constructing new green infrastructure. We have referred to a catalog of available solutions, but many other similar solutions can be plugged in.

Suggest you refer to them more in your review.

https://scholar.google.com.au/scholar?hl=en&as_sdt=0%2C5&q=tim+fletcher&btnG=

https://scholar.google.com.au/scholar?hl=en&as_sdt=0%2C5&q=ana+deletic&btnG=

https://www.melbournewater.com.au/building-and-works/developer-guides-andresources/guidelines-drawings-and-checklists/guidelines

https://waterbydesign.com.au/download-category/water-sensitive-urban-design

Answers: Thank you for the comment, the manuscript already contains 178 references and some of them are from the same authors that you have suggested. The authors believe that the mix of authors have a sufficiently representative spread (more than 5% of the articles referenced are already written by these mentioned authors).

Overall, the authors appreciate the reviewer's efforts in highlighting the various aspects that go into sizing and developing a green stormwater solution. However, the goal of the present review article is to provide interested parties with a high-level overview of stormwater management’s current state. This is attained by facilitating the development and uptake of "smarter" and more resilient urban stormwater infrastructure and proposing a decision-support matrix for developing smarter stormwater infrastructures. The authors believe that by strategically distributing these smart solutions across a watershed, it is possible to optimize stormwater infrastructure investments, get closer to a natural water cycle, and protect the environment. Because data collection is a pre-requisite for making sound decisions, including real-time control and fulfilling the need of data across various domains, efforts should be increased to collect high frequency data.

Reviewer 3 Report (New Reviewer)

The authors propose a review article focused on stormwater quality management in the Baltic Sea region. They indicate the implementation of monitoring (large-scale data collection) in the analysed systems as a useful tool for improving the quality and management of rainwater and reducing the environmental damage induced by human activities. To this end, they propose decision support tables and matrices for implementing increasingly effective (smart) solutions for rainwater management.

The present reviewer asks the authors to evaluate the following points:

Authors deal with an interesting and current issue. The aim of the work seems mainly to provide decision support tools, and I think it should be highlighted more. The aspects related to monitoring and green infrastructures are much discussed, sometimes creating confusion.

I recommend defining the goal clearly and concisely from the beginning of the work. To argue it in a flat way also in the introduction. Furthermore, the text is very reasoned, becoming dispersive in some points. So, I recommend supporting it with more graphs and images that lighten the reading and make the concepts covered clearer.

line 100-103: the definition of smart system should be reformulated to better introduce the following solutions.

line 159-162: in some parts of the text, it seems that monitoring, and therefore data collection, is the solution to many problems affecting the systems analysed. In reality, data is the basis for integrating effective systems management strategies.

Author Response

Reviewer: The authors propose a review article focused on stormwater quality management in the Baltic Sea region. They indicate the implementation of monitoring (large-scale data collection) in the analysed systems as a useful tool for improving the quality and management of rainwater and reducing the environmental damage induced by human activities. To this end, they propose decision support tables and matrices for implementing increasingly effective (smart) solutions for rainwater management.

The present reviewer asks the authors to evaluate the following points:

Authors deal with an interesting and current issue. The aim of the work seems mainly to provide decision support tools, and I think it should be highlighted more. The aspects related to monitoring and green infrastructures are much discussed, sometimes creating confusion.

Answer: The aim was not to only provide decision support tools, but instead it was to highlight the enablers and disablers of smart stormwater management in the Baltic Sea region and beyond. The article made a case for the need of smarter stormwater management as there are significant benefits that could be attained through its implementiation. The developed decision support tool is merely a roadmap for this.

Reviewer: I recommend defining the goal clearly and concisely from the beginning of the work. To argue it in a flat way also in the introduction. Furthermore, the text is very reasoned, becoming dispersive in some points. So, I recommend supporting it with more graphs and images that lighten the reading and make the concepts covered clearer.

Answer: Introduction section has ammended accordingly (line 169-177). The authors have added some illustrations for concluding certain sections and to lighten the reading (Figure 3, 5, 6).

line 100-103: the definition of smart system should be reformulated to better introduce the following solutions.

Answer: In response to the feedback, the definition of a smart stormwater system has also been revised.

line 159-162: in some parts of the text, it seems that monitoring, and therefore data collection, is the solution to many problems affecting the systems analysed. In reality, data is the basis for integrating effective systems management strategies.

Answer: The authors agree that data is the foundation upon which effective systems management strategies are established. It has been highlighted in the manuscript (line 167-171).

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Page 5, line 217 (Figure 2.): The TSS meaning remain unexplained (the term "total suspended solids” is mentioned in the text at page 6, line 277, for the first time!). I believe that this should be included in the Figure caption.

Page 6, lines 267-271: The sentence "According to Vikander et al. (2019) and Larm et al. (2010), … " should be changed in order to omit the publication years as the literature citations are given at the end of the sentence ("[53, 54]"). E.g. "According to published papers of Vikander and coworkers as well as Larm et al. …"

Page 9, line 369: The entire line "Table 2 Water" is confusing - there is no any table provided!?

Page 30, line 722; page 31, line 734, and page 32, line 767: It is (almost) impossible to read anything from the Figures 4, 5 & 6.  It should be corrected and presented clearly.

Page 34, lines 876-877: Supplementary Materials (www.mdpi.com/xxx/s1, Figure S1: title; Table S1: title; Video S1: title) is unavailable (possibly those materials doesn’t exist, and the journal templet contains this lines by default).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

See attached comments

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

In general, I found this paper to be very interesting. I found the first part of the paper, which was an overview of the topic, to be informative.  Other parts of the paper were more cumbersome to read (e.g. some of the tables were too long, some of the graphics had text that was not readable.).  These things need to be fixed.  In particular, the tables were big and difficult to read.  They did not serve as a way to quickly synthesize information.

I suggest that you eliminate the larger tables and use careful organization of text in paragraphs to replace the material in the large tables.  Some of the material in the last table is repeated in the figures that use a coding system (symbols, colors) to illustrate the different types of systems and regulations that are used in different countries-- but these figure need to be clearer.

specific text suggestions (in addition to integrating several of the tables into the text):

line 236-239 refer to  --"natural areas", which  suggests to me that these regions are not agricultural fields or fertilized lawns.  If so, they would not contribute significant amounts of nutrients (e.g., phosphorus and nitrogen).  So be specific, divide non-urban areas into appropriate land-use categories:  agricultural, natural (meaning not human-influenced)-- e.g forest or grasslands.

line 389 is a sentence fragment  There is no table 2 at this location.

line 469  to end of paragraph.  Be more specific.  Are the methods inaccurate or are the samples an incomplete representation of the water quality variations (these are two different things).  The diagram associated with this discussion is blurry and could be replaced with a more complete description of issues involved with collecting representative samples, the  time period required for analysis etc.,

Table 3:  (There is no table 2--it seems to be part of table 1).  This table with bullets is hard to read and it repeats the points made in the text.  I suggest that this table be deleted.

Table 4:  This table provides little detailed information, major relationships could reported in the literature could be presented and explained better in text form.  These somewhat generic comments are not particularly useful.

Table 5:  This table is so long (10 pages) that it defeats the purpose of a table, which is to summarize important facts, concepts, or data concisely.  Again, better to use paragraphs with headings and parallel arrangement of topics within the text.

It looks like many of the diagrams might have been developed initially as power point slides.  Below are some comments on the  figures.

Fig. 1:  This figure is a graphical representation of the previous paragraph.  It is not really needed.

Fig. 3:  This graphic is poor-quality.  The writing is blurry and difficult to read. It should be bigger and clearer-- or omit the figure.

Fig. 4:  This diagram could replace many aspects of the 10-page table if it was clearer.  I think the little scale at the top can be extended across the bottom, this would allow you to widen the whole diagram and make the text in the diagram large enough to read.

Fig. 5:  This diagram had text that was too small and too blurry to read.  If the diagram was flipped 90 degrees, you could widen the diagram and increase the font size of the text.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf