Investigating the Error Propagation from Satellite-Based Input Precipitation to Output Water Quality Indicators Simulated by a Hydrologic Model

Round 1

Reviewer 1 Report

I have found very didactical the paper, and I would like to congratulate the authors because there is a softness in the description of the technics done that helps the reader to understand all the process. Thanks. Well done!

Author Response

The Authors sincerely appreciate the Reviewer’s positive critique of the manuscript. Thank you for such a favorable response.

Reviewer 2 Report

Manuscript: remotesensing-962105

Title: Investigating the Error Propagation from Satellite-based Input Precipitation to Output Water Quality Indicators Simulated by a Hydrologic Model

Authors: Jennifer Solakian, Viviana Maggioni, Adil Godrej

Recommendation: Minor revision

Summary: This paper investigates the error propagation in three satellite precipitation products (SPPs; TMPA, CMORPH, and PERSIANN) to streamflow (Q), total suspended solids (TSS), stream temperature (TW), and dissolved oxygen (DO) through the hydrology and water quality model, Hydrologic Simulation Program FORTRAN (HSPF). The study area is the Occoquan Watershed, in the Washington, DC metropolitan area. The basin contains a number of rain gauges and six locations where the model is evaluated.

The analysis builds on the authors’ recent manuscript in Journal of Hydrology, with a seasonal component and error propagation component added to the analysis. This paper is well-written, easy to follow, and requires only some minor changes prior to publication.

Minor Comments:

1. Line 82: Typo – parenthesis instead of bracket
   
   
2. Line 191: Did the model’s land cover change in the study period 2008-2012? Please clarify.
   
   
3. Figure 2: This may an artifact of my monitors and printer or how the figure rendered in the PDF sent for review, but the minor gridlines showing the pixels for the precipitation products are hard to see. This makes it seem like the watershed is only in 2 TMPA pixels, even though it clearly spans 6 in Solakian (2019). Please double-check this prior to publication.
   
   
4. Lines 385-387: Do the authors have an explanation for why B varies so much between TMPA-Q and CMORPH-Q? There is also a basin scale dependence here (Fig 6 for Q) that should be discussed (appears in conclusions but not here).
   
   
5. Lines 482-484: Here and elsewhere, the authors attribute superior product performance to finer spatial and temporal scales. Has coarsening CMORPH, for example, been attempted to test this claim?
   
   
6. Lines 524-525: The authors should double-check the seasonal fluctuation in ambient air temperature in winter versus other seasons. It may be so for 2008-2012, but the 1981-2010 climatology at Dulles (https://www.weather.gov/lwx/iadnme) shows the largest average diurnal variation in temperature in April and October.

Author Response

The Authors thank the Reviewer for their insightful comments.  Please see below the responses directly to the Reviewer's comments. 

 

• Line 82: Typo – parenthesis instead of bracket

Thank you for catching this typo; the text in line 82 has been revised accordingly.

• Line 191: Did the model’s land cover change in the study period 2008-2012? Please clarify.

Thank you for pointing out the text is unclear about land cover used in the model. During the duration of the modelling period, land cover information is unaltered in the model. To address this question, the text in line 211 has been updated to read: “The model is updated every five years with current land use information which is unaltered during the duration of the modeling period.”

• Figure 2: This may an artifact of my monitors and printer or how the figure rendered in the PDF sent for review, but the minor gridlines showing the pixels for the precipitation products are hard to see. This makes it seem like the watershed is only in 2 TMPA pixels, even though it clearly spans 6 in Solakian (2019). Please double-check this prior to publication.

Figure 2 has been revised so that the pixel gird lines are darker and more visible. 

• Lines 385-387: Do the authors have an explanation for why B varies so much between TMPA-Q and CMORPH-Q? There is also a basin scale dependence here (Fig 6 for Q) that should be discussed (appears in conclusions but not here).

Thank for you pointing this out. Lines 391-392 of the Results section have been updated to read: “For Q, it is also apparent that B (Figure 6) has a positive dependency on basin scale but not for any of the water quality indicators.”

Furthermore, the Discussion section (lines 532-544) has been updated to the following: “The model performance (quantified by B and rRMSE in Figures 6 and 7, respectively) varies seasonally and by product, with higher Bs generally found in winter for TMPA-Q, whereas higher Bs are found in summer and fall for CMORPH-Q. These results are noteworthy since their P counterpart does not vary much by season, though summer presents higher Bs for both products. The highest Bs are found in winter for PERSIANN-Q, which corresponds to Bs associated with PERSIANN-P. One explanation as to why Bs are so different between SPP Q-simulations, especially for TMPA and CMORPH that present similar errors for P, is due to the temporal scale between products and the nature of the events (convective, stratiform, etc.), which are ultimately simulated through the model. Moreover, all three SPPs overestimate daily Q in comparison to gauge-simulated Q, which may be attributed to the fact that Q increases with drainage area (positive dependency on basin scale) causing the potential for greater residuals.”

• Lines 482-484: Here and elsewhere, the authors attribute superior product performance to finer spatial and temporal scales. Has coarsening CMORPH, for example, been attempted to test this claim? 

This is an excellent point. In this study, we are interested in assessing the performance of satellite products of different nature, i.e., different algorithms, different resolutions, different retrievals. However, if we wanted to isolate the effect of resolution, picking the finest product and aggregating it at various scales would have been a valid approach. This could certainly be the focus of a future study, which is why we updated the Conclusions section (lines 637-639) to read: “Additionally, future research should evaluate the effect of spatial and temporal resolution alone, by aggregating one of the fine resolution products to several coarser scales. Also, other SPPs should be investigated, such as IMERG,…”

• Lines 524-525: The authors should double-check the seasonal fluctuation in ambient air temperature in winter versus other seasons. It may be so for 2008-2012, but the 1981-2010 climatology at Dulles (https://www.weather.gov/lwx/iadnme) shows the largest average diurnal variation in temperature in April and October.

The Authors appreciate the suggestion to review the seasonal fluctuations in ambient air temperature during the study period. Records reveal that 2008, 2010, and 2012 were fairly average in terms of temperature and precipitation; however, the winter 2009 period shows to be slightly warmer and dryer than the long-term means for winter in this region. Also, winter 2011 was dryer and cooler than the long-term mean. While these results are interesting, the Authors believe that ambient air temperature seasonal trends play only a minor role in the results of this study since the intent is to evaluate simulated precipitation data only without alternating any other model input, including temperature. Additionally, while ambient air temperature has an impact on the output for TW and DO, temperature it is not altered in the model, therefore we believed to have an inconsequential impact in the error statistics and propagation of error.

Reviewer 3 Report

I have read with interest your paper, which discusses an interesting topic - the propagation of errors in input satellite-based precipitation products (SPPs) on streamflow and water quality indicators simulated by a hydrological model in the Occoquan Watershed, located in the suburban Washington, D.C. area. What I enjoyed particularly is the richness of the empirical material and the rigorous methodology and analysis applied to the paper.

I would however suggest the authors to:

• revise the introduction to make clearer what is the relevant literature they are contributing to
• clarify and be explicit about their research question, its originality, and importance
• include examples from other parts of the world too making it a comparative study
• Diversify their reference list, as it heavily relies to the same school of scholarship
• Better justify why the Potomac case study?
• How original is the paper compared to the following one? Solakian, J., Maggioni, V., Lodhi, A., & Godrej, A. (2019). Investigating the use of satellite-based precipitation products for monitoring water quality in the Occoquan Watershed. Journal of Hydrology: Regional Studies, 26, 100630.

Moreover, I would suggest the authors to read the following papers and explain in the paper how useful these articles are in terms of methodology (or not):

 

Li, X., Zhang, Q., & Xu, C. Y. (2014). Assessing the performance of satellite-based precipitation products and its dependence on topography over Poyang Lake basin. Theoretical and applied climatology, 115(3-4), 713-729.

 

Wang, Z., Zhong, R., Lai, C., & Chen, J. (2017). Evaluation of the GPM IMERG satellite-based precipitation products and the hydrological utility. Atmospheric Research, 196, 151-163.

 

Riad, Peter, et al. "Landscape transformation processes in two large and two small cities in Egypt and Jordan over the last five decades using remote sensing data." Landscape and Urban Planning 197 (2020): 103766.

 

Satgé, F., Ruelland, D., Bonnet, M. P., Molina, J., & Pillco, R. (2019). Consistency of satellite-based precipitation products in space and over time compared with gauge observations and snow-hydrological modelling in the Lake Titicaca region. Hydrology & Earth System Sciences, 23(1).

 

Odeh, Taleb, et al. "Over-pumping of groundwater in Irbid governorate, northern Jordan: a conceptual model to analyze the effects of urbanization and agricultural activities on groundwater levels and salinity." Environmental Earth Sciences 78.1 (2019): 40.

Author Response

The Authors thank the Reviewer for their insightful comments and suggestions.  Please find the responses directly to the Reviewer's comments as below. 

 

• revise the introduction to make clearer what is the relevant literature they are contributing to

The Authors appreciate this suggestion and have revised and rearranged the Introduction, by adding multiple references (between lines 51-127) and clarifying the current gap in literature that this work is addressing.

• clarify and be explicit about their research question, its originality, and importance

The Introduction section (lines 120-128) has been revised to better describe the research conducted as part of this study and the originality of this research to previous work.

• include examples from other parts of the world too making it a comparative study

Thank you for pointing out additional relevant worldwide research should be included in this manuscript. As part of the literature review, the Authors revised and updated the Introduction section to have include brief discussions on relevant research from the following locations: southeast U.S.; northeast U.S. (Vermont); Brazil; Japan; Iberian Peninsula; United Kingdom; Luxemburg; south India; and southwest China. Additionally, several other studies worldwide were reviewed and referenced in this manuscript though not specifically discussed in the text: Mei et al., European Alps; Zhu et al., United Kingdom; Hossain & Anagnostou, northern Italy; Satgé et al., South America; Guo et al., greater China; Hayashi et al., mid-latitude China, and Chang et al., Taiwan, among several others.

 

• Diversify their reference list, as it heavily relies to the same school of scholarship

Thank for you pointing out that referenced works are connected to the same school of scholarship. To better diversify to referenced work in this manuscript, the Authors have added 7 new references that are unaffiliated with the original referenced work (reference #s 66-72): Li et al., 2014; Wang et al., 2017; Zhang et al., 2016; Elsner et al., 2014; Raleigh et al., 2015; Yang et al., 2017; and Satgé et al., 2019.

 

• Better justify why the Potomac case study? 

Lines 142-145 have been added to include a justification for this study area, as follows: “The Occoquan Watershed is a tributary of the Potomac River, which discharges into the Chesapeake Bay, a body of water that has been a major focus scientific studies and environmental restoration efforts since the 1980s to combat pollution discharged from the watershed and the presence of aquatic dead zones in the Bay.”

 

• How original is the paper compared to the following one? Solakian, J., Maggioni, V., Lodhi, A., & Godrej, A. (2019). Investigating the use of satellite-based precipitation products for monitoring water quality in the Occoquan Watershed. Journal of Hydrology: Regional Studies, 26, 100630.

This manuscript builds upon the work presented in Solakian et al. (2019. The two studies used the same input precipitation data and modeling conditions. However, this manuscript provides an in-depth analysis of the error associated with precipitation as well as the simulated output on a seasonal basis, which was not tackled in the 2019 work. Furthermore, this study focuses on how the error propagates from the input precipitation data to the output results, which once again was not included in the 2019 study.

• Moreover, I would suggest the authors to read the following papers and explain in the paper how useful these articles are in terms of methodology (or not):

Li, X., Zhang, Q., & Xu, C. Y. (2014). Assessing the performance of satellite-based precipitation products and its dependence on topography over Poyang Lake basin. Theoretical and applied climatology, 115(3-4), 713-729.

 Wang, Z., Zhong, R., Lai, C., & Chen, J. (2017). Evaluation of the GPM IMERG satellite-based precipitation products and the hydrological utility. Atmospheric Research, 196, 151-163.

Riad, Peter, et al. "Landscape transformation processes in two large and two small cities in Egypt and Jordan over the last five decades using remote sensing data." Landscape and Urban Planning 197 (2020): 103766.

 Satgé, F., Ruelland, D., Bonnet, M. P., Molina, J., & Pillco, R. (2019). Consistency of satellite-based precipitation products in space and over time compared with gauge observations and snow-hydrological modelling in the Lake Titicaca region. Hydrology & Earth System Sciences, 23(1).

Odeh, Taleb, et al. "Over-pumping of groundwater in Irbid governorate, northern Jordan: a conceptual model to analyze the effects of urbanization and agricultural activities on groundwater levels and salinity." Environmental Earth Sciences 78.1 (2019): 40.

Thank you for pointing the Authors to these interesting papers. We included 3 out of 5 suggestions into the Introduction section of this manuscript: Li et al., 2014 [66] (lines 51-54); Wang et al., 2017 [67] (lines 58 & 60); and Satgé et al., 2019 [72] (lines 61-65). Each of these 3 articles improved the content discussed in the manuscript and provided additional support to the claims made in the study.

Round 2

Reviewer 3 Report

I have read the revised version, but I see there is still work to be done, as my comments were not fully addressed, resulting in the paper seeming still not ready for publication, unfortunately. 

In fact:

• Introduction: you still don't tell us what is the relevant literature you are addressing. You provide a brief literature review, and then say in line 123: "This work addresses a gap in the literature" but still, there's no specific information on what this literature is. Be explicit.
• Research question: previously I requested to:
  • clarify and be explicit about their research question, its originality, and importance

  your reply was:
  The Introduction section (lines 120-128) has been revised to better describe the research conducted as part of this study and the originality of this research to previous work.

  if you read carefully my request, I simply want you to tell us clearly what is the RQ. Just do so instead of telling us other things.
• My last comment was responded in this way: "Thank you for pointing the Authors to these interesting papers. We included 3 out of 5 suggestions into the Introduction section of this manuscript: Li et al., 2014 [66] (lines 51-54); Wang et al., 2017 [67] (lines 58 & 60); and Satgé et al., 2019 [72] (lines 61-65). Each of these 3 articles improved the content discussed in the manuscript and provided additional support to the claims made in the study." I did not ask you to chose 3 out of 5 (also, interestingly the authors - all based in the USA - decided to exclude the only two papers that were written by Arab scholars..). I asked you to consider all 5 papers and reflect on them and tell us how your paper relates to them. This would also help in diversifying the references you made, so inclusion of all 5 would be important.
• Also, the order of the references is wrong, and this should have been picked up and noted by the editorial team. Please fix this when revising and resubmitting.

Author Response

Dear Reviewer, thank you for your additional input.  Please see the attached file for our formal responce to comments.   

Author Response File: Author Response.docx