Water Quality Index (WQI) Analysis as an Indicator of Ecosystem Health in an Urban River Basin on Borneo Island

Round 1

Reviewer 1 Report

I have issues with the first sentence in the abstract. The health of a river system is also characterized by its ecosystem health, not just what services it can provide for humans.

In the abstract and later in results, you state that the river's health is currently moderate, but the trend shows it is improving. Elaborate on this? Have specific actions been taken to improve water quality?

On line 86, what is P67?

In the introduction, lines 116-121, you give information on two different WQI models that give a numerical value to describe water quality. For these models, what are the different categories of water quality and what numerical values are associated with each category. Without knowing this, the numbers reported are meaningless. I recommend creating a table.

Also in the Introduction, lines 145-148, you mention the DOE model, but you don't mention what water quality parameters it assesses. You mention this later in the paper (lines 188-193). I would recommend that you re-write the intro and consolidate information. There is a lot of repetition. Only mention using the DOE model and exactly what its parameters are once.

Figure 1 dies not adequately show what is referred to in the text, lines 164-176 and 188-200. Either add a second figure and/or make the first more detailed. Also, indicate the level of urbanization across these areas.

In the Methods section, lines 224-225, discuss how the sub-index value that determines the importance of different parameters is obtained? What defines "importance" with respect to parameters measured.

In the equations, lines 257-258, define all terms; n, tp.

 

Have the paper proofread by an English writer. Some sentence structure is very poor. For example, lines 71-72 is not a complete sentence.

Author Response

I have issues with the first sentence in the abstract. The health of a river system is also characterized by its ecosystem health, not just what services it can provide for humans.

Ans: Thank you. We have revised it. Please refer to the text

In the abstract and later in results, you state that the river's health is currently moderate, but the trend shows it is improving. Elaborate on this? Have specific actions been taken to improve water quality? On line 86, what is P67?

Ans: Thank you for the comments. We overlooked the typing error P (67). And we have fixed it accordingly.

In the introduction, lines 116-121, you give information on two different WQI models that give a numerical value to describe water quality. For these models, what are the different categories of water quality and what numerical values are associated with each category. Without knowing this, the numbers reported are meaningless. I recommend creating a table.

Ans: Thank you very much for your feedback. We have relocated all DOE-WQI model parameters to the method section.

Also in the Introduction, lines 145-148, you mention the DOE model, but you don't mention what water quality parameters it assesses. You mention this later in the paper (lines 188-193). I would recommend that you re-write the intro and consolidate information. There is a lot of repetition. Only mention using the DOE model and exactly what its parameters are once.

Ans: Thank you very much for your feedback. We have relocated all DOE-WQI model parameters to the method section.

Figure 1 does not adequately show what is referred to in the text, lines 164-176 and 188-200. Either add a second figure and/or make the first more detailed. Also, indicate the level of urbanization across these areas.

Ans: Thank you very much for the comments. The figure to illustrate the land use status in the study has been added to illustrate the level of urbanization. Please refer Figure 1.

In the Methods section, lines 224-225, discuss how the sub-index value that determines the importance of different parameters is obtained? What defines "importance" with respect to parameters measured.

Ans: We have revised it accordingly. We inserted this into the text. “importance” based on an opinion-poll formula where a panel of experts is consulted on the choice of parameters and on the weightage to each parameter (DOE 1985)

In the equations, lines 257-258, define all terms; n, tp.

Ans: done.

Reviewer 2 Report

I think this research manuscript (MS) is interesting, but requires considerable revision to be publishable. In my view it needs a major revision, and possibly an outright rejection.

The references are all out of order, and need to appear in numerical sequence in the MS. 

The description of the catchment, rivers and human features (slums, settlements, sewerage discharges, cleared land etc) is inadequate. The conclusion explains the importance of sewage and slums - yet this is not identified in the methods section or on the map (Figure 1).

Figure 1 is a good start - but it needs to have landuses (natural vegetation, agriculture, urban areas) included.

The methods provide some detail on the source of the water quality data - but the sampling frequency was not explained. Also some data sets were from 2014-2018 and others from 1999-2019. I would add further details to make this clear. I suggest that a table is included for each of the seven sampling locations and that the number of samples, and the time periods from which they were collected, is provided.

I remain unconvinced that the six water quality variables are justifiable for a water quality index. I would like to see the authors include a more substantial justification for this. Please remember to consider the conclusion, where conclusions about 'raw water for domestic use' and 'recreational use and navigation' are made. For these uses, faecal bacteria would be very relevant, if available. And blue-green algae?

The construction of the water quality index appears in a code formula. I would like to see this explained in clear text. Also, I do expect to see water quality guidelines that support the ratings (from very good to very bad). As this is an international journal, it is important to compare to the international literature.

The results of the water quality index are very general. I would like to see the results for each sampling site for each water quality attribute provided in a table in a summary format. This should include (1) the time period of sampling; (2) the sampling interval; (3) the minimum; (4) the maximum; (5) the mean; (6) the median. The guideline values for each - as used in the WQI should also be made available at this point. 

It looks to me that the sampling sites are mostly included in pairs. This seems to be very important. Is this upstream compared to downstream? Can the reader infer a change in water quality due to the this? Perhaps upstream is clean and undisturbed and downstream is below a town, or a sewage outfall?

Is one of the sites in this research a control reference site? That would be very helpful for comparison with the other sites. 

This is very interesting research, but in my view needs to be totally revised, in light of my comments. 

 

The MS does require further editing.

Author Response

I think this research manuscript (MS) is interesting, but requires considerable revision to be publishable. In my view it needs a major revision, and possibly an outright rejection.

The references are all out of order, and need to appear in numerical sequence in the MS. 

Ans: We have fixed it.

The description of the catchment, rivers and human features (slums, settlements, sewerage discharges, cleared land etc) is inadequate. The conclusion explains the importance of sewage and slums - yet this is not identified in the methods section or on the map (Figure 1).

Ans: Thank you very much for the suggestion. We have included the suggestion in discussion. See Figure 1

Figure 1 is a good start - but it needs to have landuses (natural vegetation, agriculture, urban areas) included.

Ans: Thank you. We have included it in the manuscript. See Figure 1

The methods provide some detail on the source of the water quality data - but the sampling frequency was not explained. Also some data sets were from 2014-2018 and others from 1999-2019. I would add further details to make this clear. I suggest that a table is included for each of the seven sampling locations and that the number of samples, and the time periods from which they were collected, is provided.

Ans: Thank you. We have done it. See Table 1

I remain unconvinced that the six water quality variables are justifiable for a water quality index. I would like to see the authors include a more substantial justification for this. Please remember to consider the conclusion, where conclusions about 'raw water for domestic use' and 'recreational use and navigation' are made. For these uses, faecal bacteria would be very relevant, if available. And blue-green algae?

Ans: The 6 parameters have been officially used by the Malaysian government through the Department of Environment (DOE) to measure the cleanliness level of rivers in Malaysia. This model has been widely adopted by numerous researchers, as evidenced by the work of Naubi et al. (2016). Therefore, we assume that there is no need for further discussion regarding this model. We have improvised and added new discussion in the method section.

The construction of the water quality index appears in a code formula. I would like to see this explained in clear text. Also, I do expect to see water quality guidelines that support the ratings (from very good to very bad). As this is an international journal, it is important to compare to the international literature.

Ans: The ‘very good to bad rating’ is based on the water quality index categorization that has been commonly used by the Department of Environment in Malaysia. Therefore, in our opinion it does not need to be described in text because it would be redundant with the method used by the DOE.

 

This has been added to the text.

“Based on twenty-one different WQI models review by Uddin et al, DoE-WQI is one of the eight major WQI model in the world [90]”

 

WQ guideline base Malaysian WQ as shown at Table 2.

The results of the water quality index are very general. I would like to see the results for each sampling site for each water quality attribute provided in a table in a summary format. This should include (1) the time period of sampling; (2) the sampling interval; (3) the minimum; (4) the maximum; (5) the mean; (6) the median. The guideline values for each - as used in the WQI should also be made available at this point. 

Ans: Number 1 and 2 have been indicated in Table 1. Numbers 3 to 6: Stated in Table 3, 4, 5, 6. Guidelines based on the Malaysian DoE classification are indicated at the bottom after the respective tables.

It looks to me that the sampling sites are mostly included in pairs. This seems to be very important. Is this upstream compared to downstream? Can the reader infer a change in water quality due to the this? Perhaps upstream is clean and undisturbed and downstream is below a town, or a sewage outfall?

Ans: As this data is obtained entirely from the authoritative source, namely the Department of Environment (DoE) Malaysia, the sampling stations are determined according to the locations specified by DoE.

Is one of the sites in this research a control reference site? That would be very helpful for comparison with the other sites. 

Ans: It is quite difficult to find a control station. Therefore, the classification as shown in Table 2 is used as a control reference.

This is very interesting research, but in my view needs to be totally revised, in light of my comments. 

 

Reviewer 3 Report

The manuscript is interesting, but must be significantly improved since it lacks consistency. The following are the main remarks:

Throughout the text, reference numbers must be rendered from 1 to 104 instead of the alphabetical order.

Methods: the description of the Water Quality Index must be clearcut, and all relevant information rendered into one consequent text instead of being scattered throughout the Introduction, Methods and 3.1 Pattern of Water Quality Index.

Lines 46-48. References are necessary to prove these two statements: “By that time, nearly 7 out of 10 people will be living in urban areas. Water quality poses as one of the primary challenges societies will encounter in the 21st century.”

Lines 76-79. References are necessary to prove this statement: “In residential areas, the morning period 76 exhibits the lowest dissolved oxygen (DO) concentrations and the highest values of total 77 solids (TS), turbidity, biochemical oxygen demand (BOD), total phosphorus (TP), total 78 nitrogen (TN), and E. coli.”

Lines 137-147: To make the main original message of the authors clearer, the description of the Water Quality Index must be moved to the Methods section, while trivial statements like “A healthy river basin ecosystem is important to ensure the integrity of biodiversity in order to be productive and provide beneficial services to humans”, etc. should be deleted from the Introduction.

Lines 160-162: geographical parameters (longitude, latitude, degrees °C) must be written correctly.

Lines 184-186: Figure 1 must be moved to the beginning of the description of the Study Area.

Lines 382-383 must be moved to the Introduction.

Lines 414-421 must be moved to the Introduction.

Lines 425-428 must be moved to the Introduction.

Lines 430-431: trivial statement must be deleted.

Lines 450: trivial statement must be deleted.

There are quite a few typos, which must be corrected.

Author Response

The manuscript is interesting, but must be significantly improved since it lacks consistency. The following are the main remarks:

Throughout the text, reference numbers must be rendered from 1 to 104 instead of the alphabetical order.

 

Ans: Thank you. We have fixed it

 

Methods: the description of the Water Quality Index must be clearcut, and all relevant information rendered into one consequent text instead of being scattered throughout the Introduction, Methods and 3.1 Pattern of Water Quality Index.

 

Ans: Thank you. We have included this suggestion in the text.

 

Lines 46-48. References are necessary to prove these two statements: “By that time, nearly 7 out of 10 people will be living in urban areas. Water quality poses as one of the primary challenges societies will encounter in the 21st century.”

 

Ans: Thank you. We have inserted the reference. Please refer the manuscript

 

Lines 76-79. References are necessary to prove this statement: “In residential areas, the morning period 76 exhibits the lowest dissolved oxygen (DO) concentrations and the highest values of total 77 solids (TS), turbidity, biochemical oxygen demand (BOD), total phosphorus (TP), total 78 nitrogen (TN), and E. coli.”

 

Ans: Thank you. We have inserted the reference. Please refer the manuscript

 

 

Lines 137-147: To make the main original message of the authors clearer, the description of the Water Quality Index must be moved to the Methods section, while trivial statements like “A healthy river basin ecosystem is important to ensure the integrity of biodiversity in order to be productive and provide beneficial services to humans”, etc. should be deleted from the Introduction.

 

Ans: Thank you. We have moved it to the methods section. We have deleted the trivial statement.

Lines 160-162: geographical parameters (longitude, latitude, degrees °C) must be written correctly.

Ans: Thank you very much. We have fixed it accordingly.

Lines 184-186: Figure 1 must be moved to the beginning of the description of the Study Area.

 

Ans: Thank you. We have done it accordingly. Please refer the text.

 

Lines 382-383 must be moved to the Introduction.

 

Ans: done

 

 

Lines 414-421 must be moved to the Introduction.

 

Ans: Thank you. Ok. This finding is used to support the argument of high NH3-N levels in the study area.

 

Lines 425-428 must be moved to the Introduction.

 

Ans: done

 

Lines 430-431: trivial statement must be deleted.

 

Ans: done

 

Lines 450: trivial statement must be deleted.

 

Ans: done

 

 

Round 2

Reviewer 3 Report

The manuscript was substantially improved and suitable for publishing. No further remarks.