Nutrient Pollutants in Surface Water—Assessing Trends in Drinking Water Resource Quality for a Regional City in Central Europe
Jonathan Miller
Round 1
Reviewer 1 Report
The paper falls within the Aims and Scope of the Journal. The manuscript has correct structure and up-to-date references. The methods are adequately described. Conclusions are sufficiently supported by data. The used data resources and methods permit replication of experimental work by other researchers.
I hope that the drawings (charts) in the final version of the work will be in good resolution.
Fig. 4 a - please change comas for dots (0,40 for 0.40).
Author Response
Authors' Responses to Reviewer's Comments (Reviewer 1)
The authors would like to thank Reviewer 1 for the thorough review of our manuscript and for providing us with their comments and suggestions on how to improve the quality and clarity of the manuscript.
Please find a list of all the answers to the Reviewer's comments below.
Reviewer #1 wrote: I hope that the drawings (charts) in the final version of the work will be in good resolution.
Our response: The quality of all charts has been improved (600 dpi).
Reviewer #1 wrote: Fig. 4 a - please change comas for dots (0,40 for 0.40).
Our response: The comment has been taken into consideration . Figure 4 has been corrected.
Reviewer 2 Report
This study looked at water quality trends in the Wislok River near Rzeszow, Poland. Mann-Kendall statistical analysis was used to detect temporal trends in water quality. The UMann-Whitney test was then used to compare winter/summer values. Finally, the paper concludes by talking about the level of water quality in the Wislok River now and the implications for water treatment processes for withdrawn water.
Major Revisions: There are three major points that I feel need major revisions in order for this manuscript to be publishable. The first has to do with the writing structure. Often, the topic sentences of paragraphs are buried inside the paragraph while a relatively minor point is presented first. The Results/Discussion section is also very long and not easy to get through. More organization would help in this section. Second, analysis of the statistical results was not very detailed or exact, and additional avenues of analysis were not presented. For example, the author states that nitrite is the only water quality indice that is increasing and then says several sentences later that it has an insignificant trend. This confusion could be made clearer by more editing. As it is presented, it does not make much sense. Additional seasonal analysis would also be nice to add. Finally, though your trend analysis is ok based on the distribution of the data, why not also do a linear regression (maybe with a log transformation) to compare results. It seems as if you did this in Fig 3 (though these graphs are unclear), but you did not compare and contrast these results to the non-parametric analysis. I think this would help add to your method section, since they are not particularly novel. A parametric approach might also help you make short-term predictions for the next 5-10 years.
Introduction. Material/Methods- Well written and understandable. I think there is too much detail at times though. A few words might be expressed differently: “Throughput (discharge)”, Anthropopressure (Anthropogenic factors),” “area pollution” (non-point source pollution) etc. for a broader audience.
Scope of Research- This section needs more work particularly on its organization and sentence structure (at times).
Results/Discussion- This section is very long. It might be good to split it up into subsections in order to present and discuss the material in a more organized way.
Conclusions- This section is very short. Only practical implications for water treatment were discussed. It would be more interesting if you discuss conclusions of the analysis for seasonal differences as well and whether your methods seemed to work. You could also discuss alternative methods as well.
Specific comments:
Line 85- unclear language about the point.
Lines 90-95- These are all per year also right?
Line 113-114 – Unclear and confusing sentence.
Lines 124-136- Too much detail. If not mentioned later as important, then cut.
Lines 140-144- 1st paragraph is out of place. Line 143 should be the 1st paragraph probably.
Line 188 – “show evidence”
Line 195-198- Why only winter and summer. Your graphs farther on show that maybe Fall or Spring are important as well.
Line 208-210- Need to edit this sentence. Confusing.
Line 227-229 – Unneeded I think.
Line 253-260- This paragraph begins saying nitrite is increasing and ends saying it is insignificant. I think the topic sentence is not saying the most important point.
Fig. 2 is too much for the manuscript. Maybe it should be in SI or reduced in some way?
Fig.3 – Hard to see. Make a clearer background and larger points maybe.
Line 285- What does .0005 mg dm3 per month really mean for water quality? Does it mean anything? It might be significant, but so small that it has little long term effect on the river.
Fig 4- Nice graphs. Thank you for including them. I think these imply you need to use 4 seasons, not just two. Make sure you discuss the reasons why these seasonal effects are important.
Line 351- 9.3, not 8.3%
Line 390-91- This sentence seems out of place and unsupported by the rest of the results.
Line 403-407- Expand on this more particularly if using more seasons.
Line 407- end- Good to connect the water quality to management implications. Try to be more clear about what Class I classification might mean. Also, you got this based on just one year. Is that justified? There are no results showing data from only that year. Maybe it was just a good year. Do you expect this to continue or rise again and why?
Author Response
Authors' Responses to Reviewer's Comments (Reviewer 2)
The authors would like to thank Reviewer 2 for the thorough review of our manuscript and for providing us with their comments and suggestions on how to improve the quality and clarity of the manuscript.
Please find a list of all the answers to the Reviewer's comments below.
Reviewer #2 wrote: Introduction. Material/Methods - Well written and understandable. I think there is too much detail at times though. A few words might be expressed differently: “Throughput (discharge)”, Anthropopressure (Anthropogenic factors),” “area pollution” (non-point source pollution) etc. for a broader audience.
Our response: The comment has been taken into account.
Reviewer #2 wrote: Scope of Research - This section needs more work particularly on its organization and sentence structure (at times).
Our response: The comment has been taken into consideration. The text has been corrected concerning the organization and sentence structure of the section. (Where necessary).
Reviewer #2 wrote: Results/Discussion- This section is very long. It might be good to split it up into subsections in order to present and discuss the material in a more organized way.
Our response: The comment has been taken into account. The text has been split into subsections, as suggested.
Reviewer #2 wrote: Conclusions- This section is very short. Only practical implications for water treatment were discussed. It would be more interesting if you discuss conclusions of the analysis for seasonal differences as well and whether your methods seemed to work. You could also discuss alternative methods as well.
Our response: We have conducted a comparative analysis for both the winter and summer half-year, although it might have not been clear from the paper.
Reviewer #2 wrote: Line 85 - unclear language about the point.
Our response: The following correction was made to clarify the location of the measuring-control point - A measuring-control point was situated at 67.9 km of the Wisłok River in the Rzeszów-Zwięczyca quarter, at the mouth of the river to the Rzeszów Reservoir (Figure 1).
Reviewer #2 wrote: Lines 90-95- These are all per year also right?
Our response: Yes, the data refer to specific years (2004 and 2013). The aim was to compare the changes over 10 years.
Reviewer #2 wrote: Line 113-114 – Unclear and confusing sentence.
Our response: Typology of surface waters has been developed for the needs of water management. It has been included in the Framework Water Directive.
Reviewer #2 wrote: Lines 124-136- Too much detail. If not mentioned later as important, then cut.
Our response: The comment has been taken into account.
Reviewer #2 wrote: Lines 140-144- 1st paragraph is out of place. Line 143 should be the 1st paragraph probably.
Our response: The comment has been taken into consideration.
Reviewer #2 wrote: Line 188 – “show evidence”
Our response: The values of Z statistics were presented in Table 2.
Reviewer #2 wrote: Line 195-198- Why only winter and summer. Your graphs farther on show that maybe Fall or Spring are important as well.
Our response: The Authors considered the winter and summer half-years because of the year division into vegetation and non-vegetation period.
Reviewer #2 wrote: Line 208-210- Need to edit this sentence. Confusing.
Our response: the introductory paragraph about drinking water assessment has been corrected.
Reviewer #2 wrote: Line 227-229 – Unneeded I think.
Our response: The comment has been taken into account.
Reviewer #2 wrote: Line 253-260- This paragraph begins saying nitrite is increasing and ends saying it is insignificant. I think the topic sentence is not saying the most important point.
Our response: The comment has been taken into account.
Reviewer #2 wrote: Fig. 2 is too much for the manuscript. Maybe it should be in SI or reduced in some way?
Our response: The comment has been taken into account. Figure 2 confirms a lack of normality of the analyzed indices distribution. Therefore we had to apply Kendall’s tau non-parametric test for the trend analysis.
Reviewer #2 wrote: Fig.3 – Hard to see. Make a clearer background and larger points maybe.
Our response: The comment has been taken into account.
Reviewer #2 wrote: Line 285- What does .0005 mg dm3 per month really mean for water quality? Does it mean anything? It might be significant, but so small that it has little long term effect on the river.
Our response: This is a monthly decrease in PO4 concentrations.The decline over 10 years reached 0.06 mg·dm-3.
Reviewer #2 wrote: Fig 4- Nice graphs. Thank you for including them. I think these imply you need to use 4 seasons, not just two. Make sure you discuss the reasons why these seasonal effects are important.
Our response: Only winter and summer half- years have been discussed in the paper, because its main subject is the trend of changes of water quality indices values over 10 years.
Reviewer #2 wrote: Line 351- 9.3, not 8.3%
Our response: The comment has been taken into account.
Reviewer #2 wrote: Line 390-91- This sentence seems out of place and unsupported by the rest of the results.
Our response: The comment has been taken into account.
Reviewer #2 wrote: Line 407- end- Good to connect the water quality to management implications. Try to be more clear about what Class I classification might mean. Also, you got this based on just one year. Is that justified? There are no results showing data from only that year. Maybe it was just a good year. Do you expect this to continue or rise again and why?
Our response: Average value of total Kjeldahl nitrogen in 2013 was below 1mg ·dm3, which allows to classify the water as class I, i.e. the maximum (best) potential. Also the trend of changes indicates the water quality improvement over 10 years and the decrease is constant, therefore it may be predicted that over the following years the water will also be in the first class.
Reviewer 3 Report
The paper is descriptive and has no scientific merit. It just reports some data with no comments, no tentative to explain the values. Most of the information are well known and do not have any originality.
Author Response
Authors' Responses to Reviewer's Comments (Reviewer 3)
The authors would like to thank Reviewer 3 for the thorough review of our manuscript and for providing us with their comments and suggestions on how to improve the quality and clarity of the manuscript.
Please find a list of all the answers to the Reviewer's comments below.
Reviewer #1 wrote: The paper is descriptive and has no scientific merit. It just reports some data with no comments, no tentative to explain the values. Most of the information are well known and do not have any originality.
Our response: Non-standard statistical methods used in the paper are original research methods. The manuscript is a valuable research material for persons responsible for water management in a catchment. It is a case study for further discussion.
Reviewer 4 Report
Dear Authors,
The work is interesting and well described, but I did not understand how this work is related with sustainability.
The introduction is burdened by a huge number of citations, more citation from 2017-2018 are necessary.
The text is relatively easy to understand by scientists in other disciplines.
Materials and Methods clearly described.
The results and discussion is clear and detail described.
Conclusion can be written like suggestion for companies which will use the Wisłok River for water treatment.
Author Response
Authors' Responses to Reviewer's Comments (Reviewer 4)
The authors would like to thank Reviewer 4 for the thorough review of our manuscript and for providing us with their comments and suggestions on how to improve the quality and clarity of the manuscript.
Please find a list of all the answers to the Reviewer's comments below.
Reviewer #1 wrote: The work is interesting and well described, but I did not understand how this work is related with sustainability. The introduction is burdened by a huge number of citations, more citation from 2017-2018 are necessary. The text is relatively easy to understand by scientists in other disciplines. Materials and Methods clearly described. The results and discussion is clear and detail described. Conclusion can be written like suggestion for companies which will use the Wisłok River for water treatment.
Our response: Our research results from the implementation of the Framework Water Directive. FWD lays down basic rules of the sustainable water policy. On this basis social, environmental and economic issues are addressed in view of sustainability. Improvement of water quality is essential to accomplish the goal of sustainable development.
A majority of cited references were published over the last three years. Some older positions on the list contain the source data providing the basis for presented research methodology.
Round 2
Reviewer 2 Report
Thank you for addressing the majority of my comments. I think your work is interesting and hope you continue expanding it.
Author Response
We would like to thank Reviewer 2 for the thoughtful and comprehensive review of our manuscript. We believe that the comments have identified important areas which required improvement. After completion of the suggested edits/modifications, the revised manuscript has benefitted from an improvement in the overall presentation and clarity.
Reviewer 3 Report
I'm not convinced
Author Response
As a response to the review (Round 1):
Originality of the methods:
The authors of the paper proposed an original methodology for data processing. The applied statistical methods concerning the trends are not used in standard water quality evaluation for the purposes of monitoring. Moreover, the methodology does not imitate the solutions provided in other publications. The analyses of trends in the variability of nutrient content in a 10-year period were conducted with use of the non-parametric Mann-Kendall test at a level of significance α = 0.05 (p-value). It consists in verifying the hypothesis on the absence of a trend in data based on a non-parametric correlation coefficient. The non-parametric equivalent of the correlation coefficient used in the Mann-Kendall test is the rank correlation coefficient of the data series and the series of their corresponding time points, also known as the Kendall tau coefficient. The changes of the analysed trends in time were described using the β slope expressed by the Theil-Sen estimator computed including all i < j (i = 1, 2, ..., n–1 and j= 2, 3, ..., n). The seasonal variability of the concentration of nutrients in the analysed period was determined based on their average monthly values in the summer and winter seasons. The material was analysed in the hydrological seasons: winter (November1 – April 30) and summer (May 1 – October 31). Statistical inference regarding the significance of any differences was conducted using the U Mann-Whitney test at the significance level α = 0.05 to check whether the parameter concentration values differed between the seasons. The measures of location: first quartile (Q1), the second (median) and third quartile (Q3) were computed for each parameter. Moreover, the methods used to assess the seasonal variability are not a standard water quality evaluation procedure, either. Our approach is different from the methodologies used by other authors, e.g. by Dąbrowska et al. [2016a and 2016b - reference 8 and 20] for waterbodies in the analysed climatic zone. The scope of our research is much wider in qualitative and quantitative terms and it differs significantly from other studies, e.g. with respect to the analysis of seasonal variability and considering the approach to the utility values of waters. Each of the applied specific statistical methods was enriched, which broadens the scope of analysis and the possibilities of result interpretation. This provides an opportunity to discuss the results with other authors, although it is certainly not a repetition of already published methods. The applied tests and methods are not elements of the statistics provided in the academic publications referred to in our paper. They were published in renowned journals and they are a scientific approach to processing water quality data.
The water cleanliness classes and limit values of specific parameters as provided in the Regulation of the Minister of Environment dated 22 October 2014 were used only to point out the scope of changes with respect to the analysed parameters and to refer them to objectively determined threshold values as well as to consider the possibility to apply standard treatment processes.
Originality of the hypothesis and results:
Many European waterbodies are qualified with a bad ecological status. In the last few years the status of European waters has improved by only 10%. The case presented in our paper is significantly different from most catchment areas, where such improvement was not noted (as we pointed out in the Discussion section). The paper also contains newly reported data from the first stage of WFD implementation. The next stage will end in 2021. The analysed period covers years, in which important changes were introduced to legislation with respect to the protection of water resources in Poland, as a result of the implementation of European laws and the accession of Poland to the EU. The aim of the common European water policy, based on a transparent, efficient and consistent legislatory framework is to improve water protection and to provide reasonable protection and use of water resources, in compliance with the principle of sustainable development and in order to satisfy the demand for water in the whole population, agriculture and industry. The results of such evaluation are particularly valuable in water management. They are the basis for the adaptive approach (management compliant with the most recent trends) that is based on drawing conclusions from the implemented measures and procedures. Adaptive management is defined as a systematic process for improving management policies and practices by learning from the outcomes of implemented management strategies.
Researchers and policy-makers all over the world are seeking for case studies that would show good examples of catchment management that result in an improved quality of natural water bodies, high quality and reliably delivered water for human use. Such cases are much less frequent than those that report lack of changes or the deterioration of water quality. The use of numerous parameters, the application of a combination of methods available in statistical software packages (to show the whole spectrum of data variability) as well as referring the changes to commonly known standards facilitates analysing the case study and comparing the obtained results with those from research in other catchments. In our opinion the citation count is the main way to measure the impact or importance of research. The possibility to reproduce part of our research or to refer other authors’ studies to our methodology is high, even more so, as the problem presented in our paper is global, it is an important current issue and it is widely discussed in literature.
The authors would like to thank Reviewer 3 for the thorough review of our manuscript and for providing us with their comments and suggestions on how to improve the quality and clarity of the manuscript.
