Monitoring Surface Water Dynamics in Mining Areas Using Remote Sensing Indices: A Review and Cross-Case Analysis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Specific Comments

• MODIS spatial resolution

The manuscript refers to MODIS as providing high-resolution imagery. This is incorrect. MODIS is a moderate-resolution sensor (250 m, 500 m, and 1 km, depending on the band). Please revise this wording accordingly.

• Landsat description

Ensure consistent descriptions of Landsat resolution. Landsat multispectral bands have a 30 m resolution (except for the panchromatic band, which has a 15 m resolution, and the thermal bands, which have a 60–120 m resolution, resampled to 30 m). If the manuscript mentions “10 m resolution” for Landsat, that would be inaccurate—it applies to Sentinel-2, not Landsat.

• Remote sensing indices

NDWI, MNDWI, and other water indices are mentioned, but some descriptions are vague. For instance, NDWI (McFeeters, 1996) and MNDWI (Xu, 2006) serve different purposes (general water detection vs. suppressing built-up land noise). It would improve clarity if the paper distinguished them.

• Use of terminology

At some places, the term “ground truth” is used loosely. A more precise phrasing would be “in-situ data” or “field measurements.”

• Reference updates

While the review cites some classic sources, more recent studies (past 5 years) on high-resolution commercial satellites (e.g., PlanetScope, WorldView) and UAV-based approaches could be added to strengthen the review.

• Unclear statement on machine learning

The section discussing “machine learning for water classification” is somewhat general and does not clearly separate supervised vs. unsupervised approaches. A short clarification could avoid confusion for readers less familiar with the field.

• Typographical and formatting issues

A few inconsistencies in citation style (e.g., “et al” vs. “et al.”). Please check the manuscript against the journal’s reference style.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript focuses on the monitoring of surface water dynamics in mining areas. The author evaluates the application of three spectral water indices through specific case studies. The topic is of scientific interest, and the manuscript provides a detailed analysis. The current version still presents some issues that need to be addressed before publication. My specific comments are listed below.

 

1. Introduction: There are two subsections both labeled 1.1 (“1 Water in mining” and “1.1 Research gap and aim of the study”). The second paragraph emphasizes the general importance of water resources, which seems unnecessary. Furthermore, the Introduction is fragmented, with two subsections and multiple short paragraphs that make it challenging for readers to follow the narrative. To address this, I recommend removing the subsections and combing related content.
2. Lines 136–139: It has already been discussed in the introduction and should be removed to avoid redundancy.
3. In Section 3.4.1, the description of data selection (Lines 482–485) should be presented at the beginning of the subsection for better logical flow.
4. In Section 3.4.3, the author discusses threshold selection of spectral water indices to differentiate surface water from other land cover types and cites multiple references with different threshold values. However, the study does not clearly explain the criteria for threshold selection in the case studies presented in this manuscript. This should be clarified.
5. The description in Lines 653–654 regarding the spatial distribution of water pixels is not directly related to Figure 13. I suggest moving this part to the following paragraph.
6. The manuscript structure requires significant improvement. There are too many short paragraphs, and figures often separate closely related information, which makes the structure appear fragmented. For example, the content in Lines 552–558 and 561–566 both refer to Figure 5, yet they are separated, while Lines 566–568, which introduce Figure 6, are separated with Lines 571– Similar issues occur throughout the manuscript. I recommend reorganizing and merging related paragraphs to enhance the overall coherence.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

• Surface water is water that exists on the surface of the Earth's crust and is exposed to the atmosphere. It is a general term for four types of water bodies: rivers, glaciers, lakes, and swamps. Surface water refers to the general term for dynamic and static water on the surface of land, including various liquid and solid water bodies. The main research object of this manuscript is liquid surface water. The remote sensing indices used are mainly used for liquid surface water. How to use remote sensing technology to monitor solid surface water?
• Surface water dynamics is the discipline that studies the motion laws of surface water, as well as their interactions with boundaries. Surface water dynamics is different from surface water. Remote sensing mainly identifies and detects the range and area of surface water. How to monitor surface water dynamics with RS indices?
• What is the impact of remote sensing data, which has errors and resolutions, on the results of surface water detection?
• The mining area is generally limited in scope, making it difficult to form a complete watershed. The study of surface hydrodynamics in this mining area has caused certain difficulties with RS technology.
• The manuscript provides three mining area cases that are relatively close to each other. They may have similar hydrological characteristics and dynamic laws. More cases with different characteristics should be provided.
• There are multiple RS indices. The applicability analysis of RS indices should be strengthened in combination with the natural environment of the mining area.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The development of the mining industry leads to significant and sometimes irreversible environmental impacts. Therefore, environmental monitoring is one of the key measures for its protection. In recent decades, remote sensing methods for obtaining spatial data have been increasingly advanced. This review focuses on the use of remote sensing indices for monitoring surface water dynamics in mining areas. The authors evaluated the effectiveness of selected spectral indices for water detection and change analysis, providing recommendations for their application. One critical conclusion is that none of the spectral indices (NDVI, NDWI, MNDWI) is universally optimal for water detection in mining regions. Their accuracy depends on landscape type, mining stage, and waterbody characteristics. This finding contradicts many previous studies that often propose a single “optimal” index for water monitoring. The authors very successfully presented an overview of spectral indexes in the form of a table, revealing their benefits and limitations.

However, in our opinion, the manuscript cannot be classified as a "Review" type, since the data in the "Results" section, apparently, had not been published before. It is better to classify the manuscript as an "Article" type.

There are some comments to the drawings. It is necessary to increase the font size of the text in Fig. 3; 6 b, c, d; and 9 b, c, D. The name of Figure 11 must be aligned with the text (lines 629-630).

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

All of my previous concerns have been adequately addressed in the revised manuscript. The authors have made the necessary clarifications and improvements. I recommend the manuscript be accepted for publication after small adjustment.

1. Keywords: the phrases "post-mining" and "post-mining lakes", one of them is recommended to be deleted.
2. Please delete "1.1. Research gap and aim of the study".

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed all comments and proposals.

Author Response

Dear Reviewer,

Thank you for the positive feedback and inspiring specific comments.