Simulation of Flow and Agricultural Non-Point Source Pollutant Transport in a Tibetan Plateau Irrigation District
Round 1
Reviewer 1 Report
In this study, the authors have investigated the agricultural non-point source pollution (ANPS) load discharged into rivers from an irrigation district in the Tibetan Plateau. Apart from conducting the experiment for two seasons, they have also simulated ANPS load using a distributed model that includes of flow calculation, and ANPS transport and transformation processes in the soil and rock. The study is technically sounds and warrants a publication in an international journal. However, there are few issues, which need to be resolved before accepting the manuscript for publication.
1) A major problem of the manuscript is the low quality discussion of the results under “results and discussion” section. The authors have only reported the results and there are no explanations or interpretations for almost all these observations, which made the manuscript more like a technical report instead of a scientific paper. Not a single citation appears under results and discussion section.
2) The manuscript also contains many grammatical errors. I have noted few errors below. Please have it edited by a fluent English user or a native speaker.
Other minor issues:
a) Page 1, Line 28-31: You have listed three statistical measures (NSE, RMSE and CD) for three variables (flow, ammonium and nitrate). I was expecting 9 numbers (3 NSE, 3 RMSE and 3 CD). However, you have listed just three numbers. What are the numbers you reported?
b) Page 2, line 40: The terminology “irrigation area” does not sound right. Please change it to “irrigated area” throughout the manuscript. Please change “Irrigation areas are the largest contributors to..” to “Irrigated areas are one of the largest contributors to….)
c) Page 2, line 55: “agricultural irrigation areas” should be “ irrigated areas”.
d) Page 2, line 71-76: Are these statements taken from a scientific report/paper? Please provide a citation to strengthen your statement.
e) Page 3, line 119: please use “hectare”, a more standard area unit.
f) Page 9: For Equations 8 and 9, please use S (or some other alphabet) to denote the slope instead of R to avoid confusion. You are using R for hydraulic radius already. My suggestion is to change S (unit flow) to q as well.
g) Page 12, lines 300-303: Please move second sentence (rainfall data) at the beginning of the paragraph for a better flow.
Author Response
In this study, the authors have investigated the agricultural non-point source pollution (ANPS) load discharged into rivers from an irrigation district in the Tibetan Plateau. Apart from conducting the experiment for two seasons, they have also simulated ANPS load using a distributed model that includes of flow calculation, and ANPS transport and transformation processes in the soil and rock. The study is technically sounds and warrants a publication in an international journal. However, there are few issues, which need to be resolved before accepting the manuscript for publication.
Response: We have carefully edited the manuscript. The manuscript has been revised according to the comments and suggestions of the reviewer.
1) A major problem of the manuscript is the low quality discussion of the results under “results and discussion” section. The authors have only reported the results and there are no explanations or interpretations for almost all these observations, which made the manuscript more like a technical report instead of a scientific paper. Not a single citation appears under results and discussion section.
Response: The manuscript has been revised according to the comments and suggestions of the reviewer. We organized the Results section to show the main results. The ANPS pollution loads in the Tibetan plateau irrigation district, limitations and advantages of the proposed model, and the parameter sensitivity were discussed in the discussion section (Page 21, line 275 to Page 22, Line 425)..
2) The manuscript also contains many grammatical errors. I have noted few errors below. Please have it edited by a fluent English user or a native speaker.
Response: The manuscript has been edited thoroughly by MDPI English Editing Service. The structure, grammar, and articulation have been significantly improved.
Other minor issues:
a) Page 1, Line 28-31: You have listed three statistical measures (NSE, RMSE and CD) for three variables (flow, ammonium and nitrate). I was expecting 9 numbers (3 NSE, 3 RMSE and 3 CD). However, you have listed just three numbers. What are the numbers you reported?
Response: The mean Nash–Sutcliffe coefficients value, which was close to 0.8, and the lowest values of root mean square errors, the fraction bias, and the fractional gross error indicated that the simulated flow rates and nitrogen concentrations using the proposed method were very accurate. (Page 1, Line 28-31)
b) Page 2, line 40: The terminology “irrigation area” does not sound right. Please change it to “irrigated area” throughout the manuscript. Please change “Irrigation areas are the largest contributors to..” to “Irrigated areas are one of the largest contributors to….)
Response: The use of fertilizers in irrigation districts is considered as one of the most common source of environmental pollution [1,2]. With low-fertilizer-recovery efficiency of nitrogen in the field, a major portion of applied fertilizers is lost with various processes [3]. (Page 2, Line 38-42)
c) Page 2, line 55: “agricultural irrigation areas” should be “ irrigated areas”.
Response: Modified.
d) Page 2, line 71-76: Are these statements taken from a scientific report/paper? Please provide a citation to strengthen your statement.
Response: For example, in the Nyingchi prefecture of Tibet, irrigation districts are often located in valley terraces, where the soil layer is commonly as thin as 40–60 cm and underlain by rock comprised of loose rubble and sand gravels. Because the soil layer is relatively thin and highly permeable, it is difficult to attain direct surface runoff into rivers during the periods of rainfall and irrigation [22]. (Pag 2, 63-67)
e) Page 3, line 119: please use “hectare”, a more standard area unit.
Response: Square kilometer (km2) was used in the manuscript.
f) Page 9: For Equations 8 and 9, please use S (or some other alphabet) to denote the slope instead of R to avoid confusion. You are using R for hydraulic radius already. My suggestion is to change S (unit flow) to q as well.
Response:
Formula (7) and (8) below cannot be shown correctly. Please see the revised manuscript.
(7)
(8)
where A is the area of the drainage canal cross-section; Q is the flow rate; q is the inflow during the calculation period (as determined using Equations. (4) and (6)); h is the depth of the drainage channel; n is the Manning roughness coefficient; R and i0 are the hydraulic radius and longitudinal slope of the drainage channel, respectively; and if is the friction slope. (Page 8, line 212-217)
g) Page 12, lines 300-303: Please move second sentence (rainfall data) at the beginning of the paragraph for a better flow.
Response; The total rainfall and irrigation were 712 mm and 863 mm for the growing period of highland barley in 2014 and 2015, respectively. Figures 4a and 4b show the measured concentrations of NH4+-N and NO3−-N, respectively, at different depths and during the highland barley growing period of 2014.
(page 11, line 272-279)
Author Response File: 
Author Response.doc
Reviewer 2 Report
The authors should carefully proofread and edit the manuscript for language and style (difficult to understand sentences, repetitions).
Detailed comments:
line 40-54 Please standardize the abbreviations NPS, ANPS, NSP.
Please use ha or km2 instead of hm2 (e.g. line 100 and 119).
Results and Discussion
There is no discussion section. Please compare your results with the findings from other studies or use the studies to support a claim. Discuss the limitations and advantages of your method. The purpose of the discussion is to interpret and describe the significance of your findings in light of what was already known about the research problem being investigated. The discussion section is a crucial part of the scientific paper. Without discussion, the reliability and significance of the results obtained can not be assessed.
Author Response
The authors should carefully proofread and edit the manuscript for language and style (difficult to understand sentences, repetitions).
Response: The manuscript has been edited thoroughly by MDPI English Editing Services. The structure, grammar, and articulation have been significantly improved.
Detailed comments:
line 40-54 Please standardize the abbreviations NPS, ANPS, NSP.
Response: Modified.
Please use ha or km2 instead of hm2 (e.g. line 100 and 119).
Response: Square kilometer (km2) was used in the manuscript.
Results and Discussion
There is no discussion section. Please compare your results with the findings from other studies or use the studies to support a claim. Discuss the limitations and advantages of your method. The purpose of the discussion is to interpret and describe the significance of your findings in light of what was already known about the research problem being investigated. The discussion section is a crucial part of the scientific paper. Without discussion, the reliability and significance of the results obtained can not be assessed.
Response: We organized the Results section to show the main results. The ANPS pollution loads in the Tibetan plateau irrigation district, limitations and advantages of the proposed model, and the parameter sensitivity were discussed in the discussion section (Page 21, line 275 to Page 22, Line 425).
Author Response File: Author Response.doc
Round 2
Reviewer 1 Report
The authors have made incorporated the suggested revisions. The revised version can be accepted for publication.
Reviewer 2 Report
The article has been improved according to the reviewer's comments. The authors should specify the word "flow". The word "flow" can refer to overland flow, subsurface flow, river flow, groundwater flow... The Authors should describe the type of flow.
