The replies and the revised manuscript after comment #1 are saved in the attachment.

Thank you.

Reply to Comment #2.

Below are my responses to the reviewer's comments. 

The reviewer's comments and questions are highlighted in bold, while my replies are presented in blue, in standard text format.

In this study, the authors developed a novel lake-watershed coupled model, an enhancement of the Simulator of Hydrological Unstructured Domains (SHUD) for hydrological modelling. Qinghai Lake, a largest salt lake, also an endorheic lake, in the Tibetan Plateau was selected to validate/test the performance of the model. The results show that the model successfully simulates the discharge of the Buha River, a tributary of Qinghai Lake, and quantifies the contribution of the lake water balance. Overall, this manuscript is novel, and was well written. I recommend the publication of this manuscript for publication in HESS after some improvements.

Major comments:

1. In the Results section, the authors provide some limited information in the “Water balance of the lake”. The further quantitative information could be provided, such as the increase/decrease of lake volume in total/sub-period, and the component contribution such as precipitation, evaporation, groundwater and other changes by %.

Thank you for your suggestion. We revised the statement of water balance of the Qinghai Lake in section 3.2, as Line 281 - 342.

1. The quantitative information of lake water balance in Qinghai Lake has been reported by many previous studies. A table can be provided to compare the previous studies with this study. The advantage of this model could be emphasized. What new understanding that this model can provide compared to previous studies or models.

Thank you for your valuable suggestion.

In response to your comment, we have added a comparison of our simulation results with those reported in previous studies in our revised manuscript. Overall, the differences in the simulation results are not substantial. The most notable discrepancies are in (1) the total inflow to the lake and (2) the contribution of groundwater.

Previous studies by Cui and Li (2015, 2015a, 2016) and Li (2007) adopted data published in 1994, which estimated the total runoff into the lake at 17.78 x10^8 m³/a. However, according to the 2021 Qinghai Province Water Resources Bulletin (Qinghai Provincial Department of Water Resources, 2022), the long-term average inflow into the lake is estimated to be between 22.2-26.7 x10^8 m³/a. Given its more recent survey, this latter data is considered more reliable, and our simulation results are closer to these estimates.

Our coupled model calculates the groundwater inflow into the lake only through the lake's adjacent elements, which are relatively few in number. Groundwater under distant elements enters through the river system before reaching the lake. Therefore, our calculated groundwater contribution to the lake is lower than the estimates in other literature.

While it's challenging to claim new findings for Qinghai Lake research from our limited data analysis, our study demonstrates that our model is a reliable tool for future research on the lake.

We have updated our manuscript to include these discussions on water balance issues in the revised version, as Line 281 - 342.

Specific comments:

• “Qinghai Lake” could be added to the title.

The suggestion is accepted. Since the Qinghai Lake is an exemplary application of the new model, the revised title is "Advancing Understanding of Lake-Watershed Hydrology: A Fully Coupled Numerical Model Illustrated by Qinghai Lake"

• Introduction. An introduction explaining why Qinghai Lake was chosen could be added.

Thank you for your suggestion. In response, we have revised the introduction to concisely explain our choice of Qinghai Lake as the study site:

"In this study, we aim to develop and validate a fully coupled lake-watershed hydrological model, with Qinghai Lake in China serving as the primary test site. Qinghai Lake, being the largest lake in China, offers unique hydrological and environmental characteristics that make it an ideal location for our research. Its endorheic nature simplifies the interactions between the lake and its watershed, which is beneficial for testing our model. The wealth of existing research data on Qinghai Lake's hydrology, ecology, and climate is invaluable for both calibrating and validating our model. Furthermore, the lake's high-altitude, cold, and arid conditions make it a representative case study for similar ecosystems, thereby enhancing the model's potential for interdisciplinary research and extending its relevance to other similar environments."

• The units after the number should be upright letter rather than italic.

Thank you for your feedback. We have corrected the unit formatting to upright letters throughout the manuscript in the revised version.

• L75: Suggested reference: doi:10.1080/27669645.2021.2015870

Thank you for the suggestion. We have incorporated the recommended citation (doi:10.1080/27669645.2021.2015870) into our manuscript, along with additional relevant publications from the same research group to enrich our references.

• L80: “49% of the total inflow into Qinghai Lake, approximately” to “~49% of the total inflow into Qinghai Lake”

Thanks. The sentence was rewritten as you suggestion. 

• Figure 1 can be replaced by Figure 1, and the Figure 1 is not necessary as they are very similar.

Thank you for your comment. If I understand correctly, you're suggesting that Figure 1 be replaced by Figure 5. However, we believe it's important to retain both figures. Figure 1 provides the terrestrial background and location of Qinghai Lake, while Figure 5 illustrates the domain decomposition created by the rSHUD tool. The triangular mesh in Figure 5 represents the computational domains where the algorithm is applied, offering readers a clear understanding of the model domains.

To differentiate between Figure 1 and Figure 5, we have added the following explanation:

"While Figure 5 might seem similar to Figure 1 at first glance, it specifically represents the unstructured triangular mesh model domains constructed by the rSHUD tool, highlighting the computational framework applied in our study."

• L85: correct the type of citation “biogeochemistry Su et al. (2019, 2020).”

Thanks. The typo is corrected in the revision.

• L220: “located at 99◦44′13”E, 37◦02′13”N” can be moved to the study area.

Thanks. The coordinates were  removed as you suggestion. 

• L230, L345, L260 and others: “Figure 5 elucidates the domain”, “Figures 6 and 7 show the model’s”. The writing can be improved by describing the results directly and then quoting the figures at the end of the sentence.

Thank you. The two sentences was rewritten as following:

"The domain decomposition results for the Qinghai Lake Basin (QLB) are detailed in Figure 5. "

and

"The model's ability to simulate daily and monthly discharges in the Buha River is demonstrated in Figures 6 and 7, respectively."

• Figure 8: The text size can be reduced. Please check all figures and use the consistent text size.

Thank you for your feedback. We acknowledge the importance of consistent text size across all figures for clarity and readability. We will ensure consistent text size across all figures and will make necessary adjustments in consultation with the figural editor.

• Conclusion: A sentence of lake water balance for Qinghai Lake from the evaluation of this model can be summarized.   

Thank you for your suggestion. We appreciate the emphasis on summarizing the lake water balance for Qinghai Lake from our model's evaluation. However, the primary objective of our manuscript is to introduce the model and demonstrate its potential in lake-watershed coupling research, rather than to provide a definitive conclusion on Qinghai Lake's hydrology. Ongoing research on Qinghai Lake, conducted in collaboration with other groups, is more suited to draw comprehensive conclusions about the lake's hydrology. Therefore, we have focused our conclusion on the model's capabilities and applications, leaving detailed hydrological assessments of Qinghai Lake to future, more specialized studies.