Understanding Hydrological Responses to Land Use and Land Cover Change in the Belize River Watershed

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I had the pleasure of reading the manuscript “Understanding Hydrological Responses to Land Use and Land Cover Change in the Belize River Watershed”. This study investigates the effects of land-use and land-cover change on hydrological processes in the Belize River Watershed from 2000 to 2020 using a SWAT modeling framework. The results descibe the changes in hydrological balance components and demonstrate the importance of protected forests in regulating watershed hydrology.

This work is timely and relevant because widespread forest loss and agricultural expansion continue to reshape land use in Central America, making it critical to understand how these changes affect water resources amid growing pressures from climate change and development.

The Authors employed a comprehensive, multidisciplinary approach integrating remote‐sensing‐derived land‐cover maps, soil and elevation data, and in‐situ streamflow measurements with the SWAT model, to capture both spatial patterns and temporal dynamics.

The methodology and data are thoroughly described and the procedures are clearly outlined, making the study reproducible. The results are well presented using tables, text, and graphs, and the conclusions are consistent with the findings.

Overall, the manuscript offers valuable contributions to understanding how land‐use and land‐cover change (LULCC) alters watershed hydrology in tropical, data‐scarce regions. The manuscript is worth publishing and will undoubtedly attract a broad readership.

Please find some minor suggestions below.   

Line 94: Please use “dynamics” instead of “hydrodynamics.”

Line 128: Please add space before the bracket.

Lines 126-133: Please add soil depth information.

Lines 576-577: The Authors state that overestimating CANMX is responsible for underestimating percolation, but they do not explain why this occurs. I suggest adding a sentence explaining that a larger CANMX value increases canopy interception, thereby reducing the amount of rainfall that reaches the soil surface and causing SWAT to simulate less water infiltrating to the water table.

Lines 581-583: Please clarify whether the referenced Belize studies were based on hydrological modeling or employed non-SWAT approaches (e.g., empirical monitoring).

Line 585: Is this correlation numerical (e.g., R2, p) or just qualitative?

Lines 586-587: Please change into “infiltration capacity” if that keeps your meaning.

Lines 587-588: I suggest naming which hydrological changes can be mitigated by reforestation (e.g., reduced runoff and increased percolation).

Lines 588-589: This is an important observation! The inclusion of references that indicate that reforestation (or intact forest cover) in the main and/or upper watershed areas provides hydrological benefits would strengthen this statement.

Line 599 (tab. 13): How would the Authors explain the increased percolation after deforestation in subbasin 10 and what is the physical process behind it? Could it be a specific climate- or soil-related regularity?

Line 613: The term “extreme hydrological responses” is vague. Please specify whether this refers to flood peaks, drought severity, variability in baseflow, or another metric?

Lines 613-615: A 99.18 % decrease implies that sediment yield is nearly zero after reforestation. It is a very important observation. Can the Authors report an approximate baseline sediment yield? It is difficult to determine whether a 99.18% change is plausible or might be a modeling artifact.

Line 628: Soil data, elevation data, meteorological data” can be shortened to “soil, elevation, and meteorological data.

Line 629: What “ancillary datasets” the Authors meant? Please briefly list them (e.g., land-survey records, road and irrigation network etc.).

Lines 629-630: Please add exact fraction of forest loss.

Lines 634-636: Please clarify that 16.86 % is the modeled change between the 2000 baseline and 2020 scenario.

Line 638: Please use “an 11.58%”

Lines 639-641: “Capture water in surface and subsurface sinks” is a somewhat vague. Perhaps change into "retain water as soil moisture and groundwater recharge"?

Line 645: A typo, should be “data-scarce”

Line 648: A typo, should be “streamflow”

Line 651: A typo, should be “streamflow”

Lines 654-656: The word “improve” is redundant. Please replace one of the word “improve” with “enhance” or “refine.”

 

Author Response

Comment 1: Line 94: Please use “dynamics” instead of “hydrodynamics.”

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have changed the word “hydrodynamics” to “dynamics.” This change is reflected on page number 3, line 94.

 

Comment 2: Line 128: Please add space before the bracket.

Response 2: We agree. We have added the space before the bracket. This change is located on page 3, line 128.

 

Comment 3: Lines 126-133: Please add soil depth information.

Response 3: Thank you for pointing this out. We agree with this comment. Therefore, we have added the following text “..., which can have a variable depth that reaches 25 cm in thickness and…” in page 3, lines 127-128.

 

Comment 4: Lines 576-577: The Authors state that overestimating CANMX is responsible for underestimating percolation, but they do not explain why this occurs. I suggest adding a sentence explaining that a larger CANMX value increases canopy interception, thereby reducing the amount of rainfall that reaches the soil surface and causing SWAT to simulate less water infiltrating to the water table.

Response 4: Thank you for pointing this out. To address your suggestion, we have added the following sentence “More precipitation is intercepted by the forest canopy and less precipitation falls to the ground when CANMX is large; therefore, the model simulates less water infiltrating the soil and percolating through the subsurface.” This change is reflected on page number 24, lines 581-583.

 

Comment 5: Lines 581-583: Please clarify whether the referenced Belize studies were based on hydrological modeling or employed non-SWAT approaches (e.g., empirical monitoring).

Response 5: Agree. We have added the following text “...using empirical hydrological models to investigate LULCC impacts…” to address your suggestion in page 24, lines 586-587.

 

Comment 6: Line 585: Is this correlation numerical (e.g., R2, p) or just qualitative?

Response 6: Thank you for pointing this out. There is a general positive correlation between forest cover loss and increase in the runoff. Therefore, we have modified the sentence to the following “…, and the current study has found that regions experiencing increased forest cover loss have also experienced increased runoff and sediment yields.” This change is reflected on page 24, lines 590-592.

 

Comment 7: Lines 586-587: Please change into “infiltration capacity” if that keeps your meaning.

Response 7: Thank you for pointing this out. We agree with this comment and we have modified the sentence to the following “Results from this study suggest that the infiltration capacity of the BRW has been negatively impacted by LULCC.” This change is reflected on page 24, lines 594-595.

 

Comment 8: Lines 587-588: I suggest naming which hydrological changes can be mitigated by reforestation (e.g., reduced runoff and increased percolation).

Response 8: We agree. We have added the following text at the end of the sentence to address your comment “in the watershed by reducing surface runoff and water yield.” This text was added to page 24, lines 596-597.

 

Comment 9: Lines 588-589: This is an important observation! The inclusion of references that indicate that reforestation (or intact forest cover) in the main and/or upper watershed areas provides hydrological benefits would strengthen this statement.

Response 9: We agree with this observation. We have added three references (Hamilton, 1986; Miura et al. 2015; Teal & Peterson, 2005) which indicate that restoration and reforestation in upper watersheds provide increased mitigation of runoff and erosion. 

 

We have added the sentence to the following: “Various studies have indicated that reforestation and habitat restoration activities in upper watersheds help to mitigate runoff and associated eroded sediments [104-106].” The sentence and references have been added to page 25, lines 602 - 604.

Hamilton, L.S. 1986. Towards clarifying the appropriate mandate in forestry for watershed rehabilitation and management. East-West Environment and Policy Institute, Reprint No 94, East-West Center, Honolulu. 51 p. https://www.fao.org/4/ad085e/AD085e06.htm

Miura, S., Amacher, M., Hofer, T., San-Miguel-Ayanz, J., Ernawati, Thackway, R. 2015. Protective functions and ecosystem services of global forests in the past quarter-century. Forest Ecology and Management, 352: 35-46, doi: 10.1016/j.foreco.2015.03.03

Teal, J.M., Peterson, S. 2005. Restoration Benefits in a Watershed Context. Journal of Coastal Research, 40:132-140. https://www.jstor.org/stable/25736621

 

Comment 10: Line 599 (tab. 13): How would the Authors explain the increased percolation after deforestation in subbasin 10 and what is the physical process behind it? Could it be a specific climate- or soil-related regularity?

Response 10:  Thank you for pointing this out. We have added the following sentence to explain the physical process behind it “The relative percentage of percolation increases during this period as well, which may be attributed to loss of forest cover. Their removal likely causes less water to be removed via ET, leading to increased percolation. Furthermore, the composition of the soils of this subbasin is dominated by humic nitisols which have low runoff potential.” This sentence was added to page 25, lines 613-616. 

We found a similar trend in an earlier study by Ranjan et al. (2005) which documents an increase in groundwater recharge following deforestation because the removal of vegetation cover also meant that there was less evapotranspiration, leading to the increase in water entering the soil. Additional analysis of this specific subwatershed in Belize indicates that this specific area’s soil is dominated by humic nitisols, which have low runoff potential. 

Ranjan, S.P, Kasama, S., Sawamoto, M. Ranjan, S.P, Kasama, S., Sawamoto, M. 2005. Effects of climate change and land use changes on groundwater resources in coastal aquifers. Journal of Environmental Management. 80 (2005) : 25 - 35, doi: 10.1016/j.jenvman.2005.08.008.

 

Comment 11:Line 613: The term “extreme hydrological responses” is vague. Please specify whether this refers to flood peaks, drought severity, variability in baseflow, or another metric?

Response 11: We agree. We have modified the following sentence to address your comment “In addition, this scenario highlighted the role of maintaining protected area forests in mitigating runoff and sediment-generating soil erosion in response to excessive precipitation.” This text was added to page 25, line 627- 629.

 

Comment 12: Lines 613-615: A 99.18 % decrease implies that sediment yield is nearly zero after reforestation. It is a very important observation. Can the Authors report an approximate baseline sediment yield? It is difficult to determine whether a 99.18% change is plausible or might be a modeling artifact.

Response 12: Thank you for pointing this out. We agree with this comment. For clarity, we have revised the text to the following: “Sediment yield experienced the greatest relative change compared to the other modeled variables, decreasing by 99.18% from LC2020 when compared to the alternative land cover scenario (LC2020PA), falling from 29.29 tons/km2 annually to 0.24 tons/km2 annually (Table 15).” This sentence is located on page 25, line 630 - 633. 

 

Comment 13: Line 628: Soil data, elevation data, meteorological data” can be shortened to “soil, elevation, and meteorological data.

Response 13: Thank you for pointing this out. We have removed the redundant use of “data.” It now reads as follows: “ESA CCI datasets were used to determine LULCCs in the watershed, and these were combined with soil, elevation, meteorological data, and ancillary datasets…” This change is located on page 26, lines 645-647.

 

Comment 14: Line 629: What “ancillary datasets” the Authors meant? Please briefly list them (e.g., land-survey records, road and irrigation network etc.).

Response 14: Thank you for pointing this out. We have added the ancillary datasets used. The text now reads as follows “...as ancillary datasets for protected areas, stream networks, water bodies, and river stages to build the BRW SWAT model.” This text is located on page 26, lines 647-648.

 

Comment 15: Lines 629-630: Please add exact fraction of forest loss.

Response 15: Thank you for pointing this out. We agree with your comment. We have therefore added the fraction of forest loss in the following text “...which was attributed to 66.79%, or 626.59 km2, of total forest cover loss during the study period. This text is located on page 26, lines 649-650.

 

Comment 16: Lines 634-636: Please clarify that 16.86 % is the modeled change between the 2000 baseline and 2020 scenario.

Response 16: We agree. We have added the period of time to the following sentence “Due to LULCCs in the BRW, findings from this study suggest that monthly average streamflow has increased by 16.86% from LC2000 to LC2020.” The text is located on page 26, lines 654-655.

 

Comment 17: Line 638: Please use “an 11.58%”

Response 17: Thank you for pointing this out. We have added the “an” to the text. This text is located on page 26, line 658.

 

Comment 18: Lines 639-641: “Capture water in surface and subsurface sinks” is a somewhat vague. Perhaps change into "retain water as soil moisture and groundwater recharge"?

Response 18: Thank you for pointing this out. We agree to modify the text. Therefore, the sentence is modified to the following “These results suggest that LULCCs in the BRW have decreased the ability of the watershed to retain water as soil moisture and groundwater recharge.” This sentence is located on page 26, lines 659-660.

 

Comment 19: Line 645: A typo, should be “data-scarce”

Response 19: Thank you for pointing this out. We have corrected the typo to “data-scarce.” The change is located on page 26, line 665.

 

Comment 20: Line 648: A typo, should be “streamflow”

Response 20: Thank you for pointing this out. We have corrected the typo to “streamflow.” The change is located on page 26, line 668.

 

Comment 21: Line 651: A typo, should be “streamflow”

Response 21: Thank you for pointing this out. We have corrected the typo to “streamflow.” The change is located on page 26, line 671.

 

Comment 22: Lines 654-656: The word “improve” is redundant. Please replace one of the words “improve” with “enhance” or “refine.”

Response 22: We agree. We have changed the word “improve” to “refine.” The change is located on page 27, line 675.

Reviewer 2 Report

Comments and Suggestions for Authors

The article is an application of the SWAT model and does not add new knowledge. It is just an application of already recognized methodology to a new case. The model was prepared correctly, with all required steps—a generally very classical approach to find the impact of land use change on hydrology. The paper can be interesting on a local scale, so my suggestion is to publish it.

Please explain the calculation time step. Do you use daily hydrological data for the calibration period? In row 247, there is no information about the time step of the data you use. In row 412, the information is that you use monthly average streamflow data. For the SWAT application, if you have daily data, it is too big an assumption to use monthly average data.   

Author Response

Comment 1: Please explain the calculation time step. Do you use daily hydrological data for the calibration period? In row 247, there is no information about the time step of the data you use. 

Response 1: Thank you for pointing this out. We agree with your comment. We have modified the following sentence to address the time step: “Daily average streamflow data from two gauge stations at the monthly time step were used for calibration and validation of the SWAT model: Double Run (DR) and Benque Viejo (BV).” This sentence is located on page 9, lines 248-250.

 

Comment 2: In row 412, the information is that you use monthly average streamflow data. For the SWAT application, if you have daily data, it is too big an assumption to use monthly average data.  

Response 2: Thank you for pointing this out. We agree with your comment. We have added the following text to address the time step in the following sentence: “The calibration (2000 to 2006) was performed using daily average streamflow on the monthly time step.” This sentence is located on page 15, lines 413-414.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript "Understanding Hydrological Responses to Land Use and Land
Cover Change in the Belize River Watershed" led by Nina Copeland et al. presents an investigation of impact of land use and land cover change on the hydrological processes in the Belize River basin. By a comparison experiment conducted by the SWAT model, the authors demonstrate considerable changes of hydrological components due to land use and land cover change. This study will be very interesting to policy makers and peers focusing on similar questions.

 

This manuscript presents a well-structured study on the hydrological consequences of land use change in a transboundary watershed. The use of SWAT model, integration of multiple data sources, and consideration of both protected and unprotected areas make the findings highly relevant for both scientific and policy communities. Despite some limitations due to data scarcity, the study addresses them transparently and suggests clear paths forward for future research. Given its methodological rigor, regional significance, and valuable insights, I recommend accepting this manuscript for publication.

Author Response

Thank you very much for your feedback. There were no specific comments to respond to.