Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper is overall solid and quite detailed. The idea of testing a simplified P model (SimplyP) in two contrasting Irish catchments is definitely useful, and I like the way the authors compare model behavior in surface-runoff versus groundwater-driven systems. The dataset is great, the methods are well described, and the writing is mostly clear. That said, it still feels a bit too descriptive and long, and the discussion doesn’t really “pop” — it reads more like a project report than a paper that draws out broader lessons for other researchers.

 

Comments:

 

The introduction is thorough but honestly too heavy. There’s a lot of textbook-level background on P transport and modeling frameworks (INCA-P, SWAT, etc.) that most readers already know. You could trim quite a bit and focus more sharply on what gap SimplyP is filling and why this specific comparison (surface vs. groundwater catchments) matters.

 

The methods are generally strong and well written, but some parts are over-explained while others are glossed over. For example, the description of parameter ranges and calibration steps is super detailed (almost to the point of overwhelming), while the reasoning for certain model choices (like fixing groundwater TRP at 0.03 mg/L) could use more justification. A simple schematic of the calibration process might help more than another paragraph of text.

 

The results section is solid but very descriptive — you often just say “the model underestimates X” or “overestimates Y” without digging into why. The interesting part is why these misfits happen (e.g., missing point sources, structural limits). Bringing those insights earlier would make it more engaging.

 

The discussion gets long and repetitive. You repeat the model’s good vs. bad performance multiple times instead of condensing and then expanding on what it means for future applications. I’d really like to see a tighter section focusing on: what SimplyP can do well right now；what structural limitations are obvious, and what specific tweaks could make it more generalizable (like including groundwater TRP decay).

 

Figures are fine, though quite a few could be simplified. There are a lot of time series that look similar — maybe combine or move some to supplementary material.

 

Language-wise, the paper is well written, but some sentences are very long and overly formal. A lighter, more direct style would make it easier to read.

 

The conclusion is okay but kind of safe — it doesn’t leave a strong message. You could be bolder in stating that SimplyP works well in surface-runoff systems but not yet in groundwater-dominated ones, and that this distinction should guide model use going forward.

Author Response

We thank the reviewer for their assessment of the manuscript and for the suggestions provided. A point-by-point response to all comments is outlined in the attached document.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

 

The review of the manuscript number water-3906577 should be discussed in details.

The opening statement of the introduction should begin with ‘Pollution control is of utmost significance for the preservation of surface water and ground water quality’. Here are references: Liu, Y., Li, B., Lei, X., Liu, S., Zhu, H., Ding, E., Ning, P. (2022). Novel method for high-performance simultaneous removal of NOx and SO2 by coupling yellow phosphorus emulsion with red mud. Chemical Engineering Journal, 428, 131991. doi: https://doi.org/10.1016/j.cej.2021.131991

Liu, R., Ji, W., Wang, W., Li, Y., Yin, L., Song, Y., He, G. (2025). Innovative amorphous calcium carbonate for superior anionic dye adsorption towards near-zero discharge. Separation and Purification Technology, 361, 131349. doi: https://doi.org/10.1016/j.seppur.2024.131349

Nasir et al. / Malaysian Journal of Fundamental and Applied Sciences Vol. 15, No. 6 (2019) 862-866

Discuss comparatively hydrologic models used for understanding, quantifying, and predicting how a particular catchment will respond under alternative scenarios.

The significance of the study as a derivative of a novelty statement should be reinforced.

Discuss about the strength and the limitations of e SimplyP model.

The result has presented in Fig 4 should be represented with error to reduce the variability of the data.

Beyond the representation of KGE performance, the result should be discussed comprehensively.

 

 

Author Response

We thank the reviewer for their assessment of the manuscript and for the suggestions provided. A point-by-point response to all comments is outlined in the attached document.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

It is ok for me.

Author Response

Thanks again for your reivew, it was very helpful.

Reviewer 2 Report

Comments and Suggestions for Authors

The review of the manuscript number water-3906577 needs to address the concern below

The introduction needs to be strengthened to reinforce the application of hydrological models.

Here are references: Zhao, Y., Wang, H., Song, B., Xue, P., Zhang, W., Peth, S.,... Horn, R. (2023). Characterizing uncertainty in process-based hydraulic modeling, exemplified in a semiarid Inner Mongolia steppe. Geoderma, 440, 116713. doi: https://doi.org/10.1016/j.geoderma.2023.116713

Li, F., Lu, H., Wang, G., & Qiu, J. (2024). Long-Term Capturability of Atmospheric Water on a Global Scale. Water Resources Research, 60(12), e2023WR034757. doi: https://doi.org/10.1029/2023WR034757

You, J., Wang, S., Ha, M., Kang, A., Lei, X., Chen, B.,... Chai, B. (2025). Comparative hydrologic performance of cascading and distributed green-gray infrastructure: experimental evidence for spatial optimization in urban waterlogging mitigation. Journal of Hydrology, 662, 133979. doi: https://doi.org/10.1016/j.jhydrol.2025.133979

Wei, Z., Miao, L., Peng, J., Zhao, T., Meng, L., Lu, H.,... Shi, J. (2024). Bridging spatio-temporal discontinuities in global soil moisture mapping by coupling physics in deep learning. Remote Sensing of Environment, 313, 114371. doi: https://doi.org/10.1016/j.rse.2024.114371

Li, R., Qi, X., Chen, L., Zhu, G., Meng, G., Wang, Y.,... Li, W. (2025). Hydrological processes in continental valley basins: evidence from water stable isotopes. CATENA, 259, 109314. doi: https://doi.org/10.1016/j.catena.2025.109314

Huang, E., Zhu, G., Meng, G., Wang, Y., Chen, L., Miao, Y.,... Li, W. (2025). Historical dataset of reservoir construction in arid regions. Scientific Data, 12(1), 1428. doi: 10.1038/s41597-025-05712-3

Meng, G., Zhu, G., Jiao, Y., Qiu, D., Wang, Y., Lu, S.,... Li, W. (2025). Soil salinity patterns reveal changes in the water cycle of inland river basins in arid zones. Hydrol. Earth Syst. Sci., 29(19), 5049-5063. doi: 10.5194/hess-29-5049-2025

Madan Pokhrel, Narendra Shakya, Manoj Lamichhane. Assesement of Surface Water Availability of Kathmandu Valley Using SWAT Model. Asian Journal of Water, Environment and Pollution 2024, 21(4), 1–14. https://doi.org/10.3233/AJW240041

 

Author Response

Thank you for the comment. We strengthened the introduction by more clearly outlining why hydrological and water-quality models are essential for assessing nutrient dynamics and supporting catchment-scale management. We added two references—Fu et al. (2019) and Wellen et al. (2015)—to position the study within current modelling practice and to reinforce the scientific rationale for applying and adapting hydrological models such as SimplyP.

Added references:

Fu, B., Merritt, W. S., Croke, B. F. W., Weber, T. R., Jakeman, A. J. A review of catchment‐scale water quality and erosion models and a synthesis of future prospects. Environmental Modelling & Software 2019, 114, 75–97. https://doi.org/10.1016/j. envsoft.2018.12.008.

C. Wellen, A.-R. Kamran-Disfani, G. B. Arhonditsis. Evaluation of the Current State of Distributed Watershed Nutrient Water Quality Modeling. Environmental Science & Technology 2015, 49(6), 3278-3290.

Author Response File: Author Response.pdf