Study on Spatiotemporal Transport Characteristics of Soil Moisture in Layered Heterogeneous Vadose Zone Based on HYDRAS-3D
Round 1
Reviewer 1 Report
Dear Author,
The manuscript is devoted to study on spatiotemporal transport characteristics of soil moisture in vadose zone applying HYDRAS-3D software. As far as I can see the paper is too "technical", thus I have some suggestions and comments for involving research context relating to other science issues on characterizing soil moisture using remote sensing satellite observations and in situ measurements.
Generally, the explanations you advocate for some of your findings are often devoid of sufficient literature references (either supporting or contrasting) to properly contextualize them.
Introduction:
I think you should add a paragraph concerning actual programms and research studies on monitoring soil moisture using Earth Observation data and provide the limitations of using them. As far as we all know Earth observation satellites are valuable tools for monitoring various environmental parameters, including soil moisture transport. Soil moisture transport refers to the movement of water within the soil, and it plays a critical role in various ecological and agricultural processes. Several satellites and satellite-based sensors provide data that can be used to study soil moisture transport at different spatial and temporal scales. Here are some key satellites and sensors used for this purpose with some references that are required to add: NASA's Soil Moisture Active Passive SMAP Mission (https://www.sciencedirect.com/science/article/pii/S0022169421007484), European Space Agency's Soil Moisture and Ocean Salinity (SMOS) Mission (https://www.mdpi.com/2072-4292/14/6/1419), Sentinel-1 Radar Satellites (https://www.mdpi.com/2072-4292/8/9/756), MODIS Moderate Resolution Imaging Spectroradiometer (https://www.researchgate.net/publication/264610479_Continuous_soil_moisture_mapping_using_MODIS_NDVI_and_LST_products), GRACE Gravity Recovery and Climate Experiment (https://disc.gsfc.nasa.gov/datasets/GRACEDADM_CLSM0125US_7D_4.0/summary)
What about using the L-band from Japanese ALOS-L (https://www.mdpi.com/2072-4292/6/2/1605)? Exploiting L-band of the electromagnetic spectrum for soil moisture measurement is advantageous because it allows for the penetration of microwave radiation through vegetation and the soil surface. This capability is particularly valuable in areas with dense vegetation cover, where other microwave frequencies might be obstructed. L-band sensors measure microwave radiation interactions with soil, which depend on its dielectric properties influenced by soil moisture, enabling accurate estimation of soil moisture content. This technology is crucial for applications in agriculture, hydrology, and environmental monitoring, as it provides insights into root zone soil moisture and is less affected by atmospheric interference and various weather conditions.
Methods and Results
I think the sections are written properly and figures are presented well. I can see you have done study work via comparing and analyzing the simulated and measured values in the HYDRUS-3D model, and that they showed good consistency, via verifying the accuracy and reliability of the model, and indicating that the model can be well applied in experiments. (In my opinion good work).
Discussion:
I would just suggest to add paragraph summarizing your methods and results and mentioning on applicability of machine learning techniques for simulating soil moisture transport and other variables concerning relations vegetation-soil moisture as well the impact of the vadose zone on vegetation condition. XGBoost remains a top choice in machine learning due to its efficiency, speed, and scalability, particularly with GPU support and improved tree pruning techniques. It offers robust solutions for handling missing data and categorical variables, along with enhanced model interpretability. Its active development and integration with other libraries ensure its continued relevance and usefulness in various applications. Here you can find on applicability of XGBoost at area with high water level fluctuations that we monitor regarding soil moisture and other vegetation parameters: https://www.mdpi.com/2072-4292/15/9/2392.
Best whishes
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions.[The revisions have been marked in red].
Comments 1: Should add a paragraph concerning actual programms and research studies on monitoring soil moisture using Earth Observation data and provide the limitations of using them.
Response 1: Agree. After reading several of the literature you recommended.I have add a paragraph concerning actual programms and research studies on monitoring soil moisture using Earth Observation data and provide the limitations of using them. And relevant references were added at the end of the paper.
[where in the revised manuscript this change can be found –Page 1 and 2, lines 39-47; Page 3, lines 113-114; page 21, lines 509-517.]
Comments 2: Add paragraph summarizing your methods and results and mentioning on applicability of machine learning techniques for simulating soil moisture transport and other variables concerning relations vegetation-soil moisture as well the impact of the vadose zone on vegetation condition.
Response 2: Agree. I have completed the corresponding modifications. I have added a discussion section and mentioned the applicability of machine learning technology in simulating soil moisture transport. I have proposed the idea of comparing and analyzing the simulation results of XGBoost and HYDRAS in future research to improve the accuracy of soil moisture transport models. I also added relevant references at the end. Thank you for your suggestion
[where in the revised manuscript this change can be found –Page 20, lines 456-474; Page 22, lines 579-590.]
Author Response File: 
Author Response.docx
Reviewer 2 Report
In this study, in situ experiments were conducted at the Ningxia Water and Environment Field Scientific Observation and Research Station to examine water transport in heterogeneous media. Revealed the spatiotemporal patterns of soil moisture lateral transport in the plane under the change of soil water potential at the soil layer interface. The research content is informative. However, some clarification is needed on the following comments:
1. The abstract does not highlight the research innovation.
2. The research background in the introduction does not explain what the existing problems are, and the research significance is not clear.
3. The classification basis of soil texture should be added in the materials and methods.
4. The monitoring of soil data is only monitored by soil temperature and humidity sensors, and is not verified by other methods.
5. In the conclusion part, we should point out the shortcomings of the thesis and show the limitations of the thesis.
6. Some descriptions of the language in the whole article are not standard and need to be carefully checked and revised.
Comments for author File: 
Comments.pdf
No
Author Response
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions.[The revisions have been marked in red].
Comments 1: The abstract does not highlight the research innovation.
Response 1: Thank you for pointing this out. I agree with this comment. Therefore, I added the innovation of this article in the first sentence of the abstract: The heterogeneity of layered soils affects the transport processes of water in the vadose zone; however, The mechanism of soil moisture transport in the vadose zone under heterogeneous media conditions, especially the three-dimensional transport mechanism, is a frontier problem to be studied.
[where in the revised manuscript this change can be found –page 1, Lines 10-13.]
Comments 2: The research background in the introduction does not explain what the existing problems are, and the research significance is not clear.
Response 2: Agree. I have completed the corresponding modifications. I have added issues from previous studies to my research background and explained the significance of this study.
[where in the revised manuscript this change can be found –Page 3, lines 105-110 and 119-122.]
Comments 3: The classification basis of soil texture should be added in the materials and methods.
Response 3: Agree. I have added a classification basis for soil texture in the materials and methods. The lithology of the vadose zone is complex, and the lithology of the vadose zone in the area where human agricultural production and economic activities are most frequent has been generalized. The strata within 10 meters are mainly composed of three lithological structures: (1) silty soil, silty sand, and fine sand, (2) silty soil and fine sand, (3) fine sand, silty clay, and fine sand.
[where in the revised manuscript this change can be found –Page 3, lines 134-138.]
Comments 4: The monitoring of soil data is only monitored by soil temperature and humidity sensors, and is not verified by other methods.
Response 4: Thank you for the teacher's suggestion. This in-situ test lasted for a long time, mainly by embedding soil temperature and humidity sensors in the test soil column to monitor data. In future experimental studies, other monitoring methods will be added to verify the data from multiple perspectives. I have pointed out this limitation in the conclusion section.
[where in the revised manuscript this change can be found –Page 21, lines 511-516.]
Comments 5: In the conclusion part, we should point out the shortcomings of the thesis and show the limitations of the thesis.
Response 5: Thank you for your suggestion. I have pointed out the shortcomings of the paper in the conclusion section. This article only uses soil temperature and humidity sensors as a monitoring method in the moisture monitoring of the vadose zone, and is limited to analyzing the water transport situation in heterogeneous media and constructing a three-dimensional model. The vadose zone is a three-phase structure of gas liquid solid, and multiple methods can be used to verify the monitoring data in future research, And further improve the research on gas movement in the vadose zone of heteroge-neous media.
[where in the revised manuscript this change can be found –Page 21, lines 511-516.]
Comments 6: Some descriptions of the language in the whole article are not standard and need to be carefully checked and revised.
Response 6: Thank you for your suggestion I have checked and corrected some incorrect English language in the paper. If there are still some non-standard areas, please provide suggestions again. Thank you very much.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Authors
Thank you for your replies and hard work on improving the manuscript.
Kind regards
