How Can We Represent Seasonal Land Use Dynamics in SWAT and SWAT+ Models for African Cultivated Catchments?

Round 1

Reviewer 1 Report

Review of

“How can we represent seasonal land use dynamics in SWAT and SWAT+ models for African cultivated catchments?” by Nkwasa et al.

1. 2 Input Data (Line 120)

Please give more explanation of the following questions; how can you decide to resolve the March and August maps by overlaying the three maps and replacing the unclassified pixels with corresponding pixels from one in October? Did you consider any seasonal difference between three months’ maps?

2. 4 Land use trajectory (Line 158)

Please explain how you distinguished the unrealistic trajectories which were excluded.

3. 5 Model Configuration

I think it would be better to add three seasonal land use maps for March, August and October to show the seasonal difference of land uses.

4. 2 Leaf Area Index Comparison

Please add the description of R-square and p-value with equations and the criteria for scoring the performance.

5. 2.1 Rainfed maize to irrigated mixed crops to irrigated mixed crops trajectory (Line 332)

Please give detailed explanation of the increased correlation. And what does the LAI dropped to zero highlight?

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Despite the title of the study which gives emphasis to seasonal “land use dynamic” in the SWAT model, the study has been focused only on incorporating dynamic “LAI” into the model rather than “land use” changes. Incorporating land use changes into the SWAT model means being able to capture the dynamic of land surface associated with “different land use attributes” (e.g., agriculture, urban areas, water, rock, road, etc.), both “spatially” and “temporally”. This has been clearly presented by Wagner et al. (2019) [https://doi.org/10.1016/j.envsoft.2017.06.023], and Kumar et al. (2020) [https://doi.org/10.3390/w12020410]. Wagner et al., (2019) investigated the effects of dynamic versus static representations of land use change in hydrologic impact assessments. Kumar et al. (2020) used multiple land use layers which were incorporated in the SWAT model by activating land use change (LUC) module/land use update (lup.dat) using the SWAT LUC tool (available at https://saraswat-swat.rcac.purdue.edu/). Therefore, authors should either modify the whole text (and clearly mention that the focus of the study is being only on “incorporating seasonal LAI dynamics”), or modify the methodology to incorporate the spatial and temporal land-use/cover changes in the SWAT model.

Specific comments:

• P6L181: What would be the uncertainties associated with the inbuilt weather generator (to generate the climate parameters)?
• P6L184: Yes, the Penman-Monteith method uses all the climate parameters, but are these climate parameters/data available for this study? The study uses the SWAT weather generator, since it does not have access to wind speed, solar radiation and humidity data. Why not a simple temperature-based method instead, e.g., the Hargreaves–Samani method?
• P6L200: LAI plays an important role in the hydrological cycle. Please elaborate how ignoring the calibration procedure doesn’t affect the LAI simulations in the SWAT model?
• P11L301 : What remote sensing data have been used to generate the LAI values at a 1 km resolution? What is the temporal resolution of the remote sensing data?
• Farjad et al. (2017) [https://doi.org/10.3390/w9100767] stated that “…the SWAT model uses empirical equations that were developed for the US climate conditions, which may not be suitable when applied in different climates...”. How this SWAT limitation can be addressed considering the study area of this research? Discuss this modelling limitation, along with other literatures mentioned above [Wagner et al., (2019) and Kumar et al. (2020)] in the introduction section.
• Does the SWAT model consider the root depth parameter as well ̶  or its spatial/temporal dynamics?

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

it is ready to be published 

Reviewer 2 Report

No additional comments.