Spatial and Temporal Dynamics of Key Water Quality Parameters in a Thermal Stratified Lake Ecosystem: The Case Study of Lake Mead

Round 1

Reviewer 1 Report

I advise the authors to reconsider their choice of parameters. TDS and conductivity give the same interpretation, no relevant information will be provided in analyzing both of them.  

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors, dear Editor I carefully read the manuscript “Assessment of the Spatiotemporal Trends of Total Dissolved Solids, Electrical Conductivity, and Temperature in Lake Mead ”, written by Godson Ebenezer Adjovu, Haroon Stephen, and Sajjad Ahmad. I have to conclude that I cannot recommend the publication of the manuscript. There are minor issues but my main concern is the methodology and the short comes in the interpretation. I would expect additional data analysis and analysis of time series to be able to understand the dynamics of the system. Why did the authors not include important information in their analysis such as: the water level changes, the amount of influx and outflow, evaporation, and the anthropogenic input of treated wastewater into the lake? In conclusion, the manuscript's scientific importance is low and no interesting methods are developed or applied. Some other important issues are: Why do the authors include electrical conductivity (EC), and total dissolved solids (TDS) into their analysis? Both parameters should give nearly the same information on the variation in the mineralization of the water. If the variations are different please explain this difference. Figure 1: Map of Lake Mead modified from National Park Service [41] There is no scale, no indication of North direction, or coordinates on this very basic “map” (just the lake's contours). Please include a real map with the watersheds and the flow direction in the lake. Figure 4: Spatial Distribution of TDS Concentration How do the authors explain this difference in the mineralization and what is the flow direction? Is there no dynamic in the distribution of the TDS concentration? You show in Table 4 that the mineralization of the water has been lower in recent years although the water level fell, how can you explain this observation? Line 185-187 You state that TDS concentration is measured in the laboratory at the Clark County Wastewater facility using physical filtering (i.e., gravimetric) and drying methods, temperature, and EC measurements were performed using a YSI EXO data sonde. The frequency and measuring station are chosen based on background information, location, and relevance of these locations. Please explain more about the database for example missing values, quality of data, and so on. No information is given why the authors choose to include measurements at those sites and only between 2016 and 2021. Are these all stations or did you exclude stations and if, what was the reason Figure 5: Time Series variations of WQPs at the sampling locations Are these data from all stations in one figure? Line 22-24 You state: “The highest levels of TDS and EC were detected in the summer months owing to the increased rate of mineral dissolution and rate of evaporation with no significant difference among the values from month to month and year to year. “ This is contradictory. Please explain why there is no difference among the values from month to month if the highest levels of TDS and EC were detected in the summer months. Line 142-143 You state: “The lake experiences complete (top to bottom) mixing from late autumn to early spring and stratification from spring to autumn every other year cycle [35]”. What is the depth at which samples were taken? How is stratification reflected in the measurements and in the interpretation?

Author Response

Please see attached file for a reply to reviewer's comments 

Author Response File: Author Response.docx

Reviewer 3 Report

Dear Authors,

The manuscript "Assessment of the Spatiotemporal Trends of Total Dissolved Solids, Electrical Conductivity, and Temperature in Lake Mead" is well-written, engaging, and scientifically sound. However, the manuscript needs some formatting and extensive revision on the visualization, as elaborated below.

Line 175: The map must include latitude and longitude coordinates.

Line 199: The map must include latitude and longitude coordinates. The sampling locations and legends can be made clearer.

Line 270: The map must include latitude and longitude coordinates. The sampling locations and legends can be made clearer.

Line 290: The map must include latitude and longitude coordinates. Please indicate what the white color indicates on the map.

Line 310: Figure 5 consists of three plots. They must be individually labeled. Moreover, the labels' font size must be increased for readability.

Lines 353, 393, and 437: The visualization of Figures 6, 7, and 8 is poor and must be improved, including the label fonts, standard deviation, and the time series plot. The subplots must be individually labeled.

 

Lines 492, 494, 511, 529, 537, and 578: What does "Statistics" in the column heading refer to?

Author Response

Please see attached file for a reply to reviewer's comments 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The choice of parameters in the revised version is more explicit this time, I had the impression I am reading a totally new article with a new topic. The modifications done are interesting but the overall manuscript became too long and heavy to read. I suggest to summarize the parameters descriptions in section 2 : 'Material and Methods' and save the additional explanations to the third section : 'Results and discussion'. 

Author Response

Please see the attached reply to the reviewer's comments. 

Author Response File: Author Response.docx

Reviewer 2 Report

In this new version of the manuscript “Spatial and Temporal Dynamics of Key Water Quality Parameters in a Thermal Stratified Lake Ecosystem: The Case Study of Lake Mead“ a profound rewriting of the main parts is presented, where now the water level changes, the amount of influx and outflow, and evaporation are discussed. Further analysis of the impacts on hydrological variables (like outflows, evaporation, and storage) are discussed with respect to the water quality parameters in the lake).

 

The manuscript was significantly improved, but there are still flaws to be corrected. 

Many figures do not support the text and should be corrected; some may be deleted because they do not give sufficient information.

 

Table 1. Lake Mead Sampling Station: 

The stations 1 – 4 location is indicated as: “Movable”. Please explain what this means exactly and what coordinates they move within.

 

Figure 2. :

The map should include the exact coordinates. The colors (dark grey and black) are difficult to distinguish.

 

Figure 3. :

Time Series variations of the WQPs are given for all sampling locations together and should be given separately for each station and the correlations between each station and parameters should be discussed.

 

Figure 4. Spatial distribution of the overall WQPs along the study area:

What is the date the data were taken?

 

Figure 6. Seasonal variability of key WQPs in Lake Mead under the studied period: 

Size of the figures is too small.

 

Figure 7. Seasonal spatial distribution of key WQPs in Lake Mead under the studied period located at approximately 36° 3'45.27"N, 114°45'41.25"W: 

The title of the figure is wordy

The figure "TSS in winter" is strange, which interpolation method led to this result, please explain.

 

Figure 10. Impact on hydrological factors on TSS concentration in Lake Mead.:

What does the x-axis mean (why are there 5 times values of 5?). Please correct the figure or delete it.

 

Figure 13. Time series variations of key WQPs in changing depth in Lake Mead: 

There is something wrong with the y-axis, please correct it!

 

Please check the supplementary file with the version in Word, as there are many errors from the conversation 

 

Comments for author File: Comments.pdf

Author Response

Please see the attached reply to the reviewer's comments. 

Author Response File: Author Response.docx

Reviewer 3 Report

Accept in present form.

Author Response

Please see the attached reply to the reviewer's comments. 

Author Response File: Author Response.docx