Evaluating the relative importance of precipitation,  temperature and land-cover change in the hydrologic  response to extreme meteorological drought conditions  over the North American High Plains

Hein, Annette; Condon, Laura; Maxwell, Reed

doi:https://doi.org/10.5194/hess-23-1931-2019

Articles | Volume 23, issue 4

https://doi.org/10.5194/hess-23-1931-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-23-1931-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 23, issue 4

Research article

|

10 Apr 2019

Research article |

| 10 Apr 2019

Evaluating the relative importance of precipitation, temperature and land-cover change in the hydrologic response to extreme meteorological drought conditions over the North American High Plains

Annette Hein, Laura Condon, and Reed Maxwell

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Final revised paper (published on 10 Apr 2019)
Preprint (discussion started on 02 Oct 2018)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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SC1: 'Review of "Unravelling the impacts of precipitation, temperature and land-cover change for extreme drought over the North American High Plains"', Peter La Follette, 27 Oct 2018
- AC1: 'Reply to Peter LaFollette', Annette Hein, 01 Nov 2018
RC1: 'Review of Hein et al.', Anonymous Referee #1, 28 Oct 2018
- AC2: 'Reply to Reviewer 1', Annette Hein, 16 Nov 2018
RC2: 'Review of "Unravelling the impacts of precipitation, temperature, and land-cover change for extreme drought over the North American High Plains"', Anonymous Referee #2, 02 Nov 2018
- AC3: 'Reply to Reviewer 2', Annette Hein, 16 Nov 2018

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by editor and referees) (07 Dec 2018) by Niko Wanders

AR by Annette Hein on behalf of the Authors (18 Jan 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (22 Jan 2019) by Niko Wanders

RR by Anonymous Referee #1 (19 Feb 2019)

Suggestions for revision or reasons for rejection

I thank the authors for their detailed response and the modifications of the manuscript. The authors have addressed all my comments, and some changes were made to the manuscript. These changes improved the presentation and clarity of the methods and results and increased comprehensibility. The distinction between meteorological and hydrological drought is useful and the title is much more representative of the content.

However, unfortunately, I remain disappointed by the changes made. This is mainly because the manuscript still deals with ‘drought severity’ (e.g. abstract, referring to the hydrological system, and throughout the text) without actually addressing or evaluating a hydrological drought.

The analysis that the authors provide is valid, so is the application of meteorological drought factors to a hydrological system in the state of an average water year. However, it has to be clear from the manuscript that the authors do not evaluate the hydrological drought response. They evaluate the differences to a baseline scenario, but ‘decreased runoff or soil moisture’ are not necessarily representative of a drought. A negative difference relative to a baseline (what the authors call ‘anomaly’) does not necessarily represent a drought and especially not during one ‘average water year’. I.e. the difference of ~60 mm in soil moisture relative to 330mm of soil moisture in Figure 4 does not show the ‘hydrological drought impact’ but simply the difference arising from meteorological drought. To evaluate the severity of the drought, these values should be anomalies relative to a climatology, exceeding critical thresholds of e.g. soil moisture. To evaluate a drought severity, the authors should apply an integrated measure of severity (any of the indices out there would do), that addresses the state. In my previous comment, I was also noting the ‘extent of drought’, which referred to the spatial extent of drought, e.g. as depicted by such a grid cell based index. Similarly, the authors could evaluate the effects on temporal characteristics of drought, such as the onset.

To be clear: I am not asking that the authors re-run their experiments to start from hydrological drought conditions. I am asking them to clarify the terminology of drought in the manuscript (as they do not evaluate the hydrological drought) or add some analysis, as indicated above, that addresses the simulation of hydrological drought. After these changes, the manuscript should be publishable.

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RR by Anonymous Referee #2 (01 Mar 2019)

Suggestions for revision or reasons for rejection

The paper now titled “Evaluating the relative importance of precipitation, temperature, and land-cover change in the hydrologic response to extreme meteorological drought conditions over the North American High Plains” uses ParFlow-CLM to understand how perturbations of the meteorology of the High Plains over the contiguous United States impact the hydrologic cycle. The authors have provided satisfactory responses to the majority of my comments. Although I still disagree that it is ok to simply perturb one variable at a time; I agree that this approach is common and therefore should not prevent this work from being published. In the end, however, these types of assumptions (similar to the limitation on the land cover database use) will limit how much these results can be generalized and therefore the larger impact of this study; but again that should not limit this work from being published at this time. I have one minor comment below that can be addressed at the proof stage and a more general response regarding the meteorology challenge that doesn’t necessarily need to be addressed.

Page 7; Line 16: The climate modeling community have actually put a lot of effort into developing historical land use/land cover datasets (https://link.springer.com/article/10.1007/s10584-011-0153-2) so this statement is not truly accurate. You could have chosen to use these data instead. This should at least be mentioned in the paper.

Table 1: You are correct in stating that others also use the approach of just perturbing one variable at a time. But again, this can be completely inconsistent. All the meteorology is inherently correlated; as such, varying one variable at a time does not represent a realistic scenario and can lead to misleading conclusions. In the end, I am ok with moving ahead with the simulations as is. However, I think it is a missed opportunity. Just because it has been done before does not mean there isn’t a better way. For the case of the temperature, it would have been pretty straightforward to modify both specific humidity (assume constant relative humidity) and longwave radiation (assume constant emissivity). In the end, whether it will change things dramatically is certainly debatable, but I don’t agree with the statement that changing “three at a time” would be problematic. It would still be only change temperature and then adjust variables that are strongly dependent on air temperature.

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ED: Publish subject to minor revisions (review by editor) (01 Mar 2019) by Niko Wanders

AR by Annette Hein on behalf of the Authors (09 Mar 2019) Author's response Manuscript

ED: Publish subject to technical corrections (13 Mar 2019) by Niko Wanders

AR by Annette Hein on behalf of the Authors (17 Mar 2019) Author's response Manuscript

Short summary

Drought is a natural disaster that can result from changes to temperature, precipitation and/or vegetation. Here we apply a high-resolution computer model to explore the relative importance of each factor on the North American High Plains, one of the most important agricultural regions of the USA. Decreased precipitation caused larger changes in hydrologic variables (evapotranspiration, soil moisture, stream flow and water table levels) than increased temperature or disturbed vegetation did.