Hydrological Response to Meteorological Droughts in the Guadalquivir River Basin, Southern Iberian Peninsula

Round 1

Reviewer 1 Report

The manuscript investigated the relationship between meteorological (SPEI) and hydrological droughts (SSI) using drought indices with data from 1980 to 2012. The topic is interesting and the manuscript has been written well. I enjoyed reviewing this manuscript and would like to suggest some points to enhance its quality before publication. My comments are listed below:

- Figure 1 needs a scale bar, legend, and north sign.

- A methodology flowchart is needed to illustrate the different faces of the study.

- Figures 2 (a and b) are difficult to understand. The authors are suggested to modify these figures.

- A table explaining the main features of stream gauges is suggested to be added to the manuscript.

- It was well documented that positive and negative SPEI values indicate wet and dry periods, respectively. So, is it informative to separate the relations at least into wet and dry conditions? 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Review of "Hydrological response to meteorological droughts in the Gua-2 dalquivir River Basin, southern Iberian Peninsula" by Romero-Jiménez et al, submitted to Water.

This study looks at the relationship between meteorological drought and hydrological drought in the Guadalquivir River Basin (southern Iberian Peninsula), represented by 43 reservoir stations. The authors accomplish this in three main parts, firstly, by looking at the lagged relationship (i.e., correlation) between the Standardized Precipitation Evapotranspiration Index (SPEI), which represents meteorological conditions, and the Standardized Streamflow Index (SSI), which represents the hydrological conditions. Secondly, the authors perform Principal Component Analysis (PCA) to better understand the overall spatial behaviour of drought, and thirdly, they use a multiple linear regression result to separate the influence of catchment area, soil permeability and site altitude on the PC loadings.  The results show that this using these three approaches (e.g., lagged correlation, PCA analysis, MLR), they can better understand the temporal and spatial patterns of drought over the Guadalquivir River Basin.

This study is nicely written, and quite easy to follow. I think it will be of interest to those who work in natural resource management or water policy. I suggest acceptance of this study, following some minor changes, mainly to do with presentation.

Major suggestions:

·         Figure 2 and similar plots: I have a hard time distinguishing between the different color shades, so I suggest replotting these figures (e.g., Figure 2, Figure 7, Figures 9-10) using fixed set colors that are colorblind friendly, instead of using sequential color palettes. Figure 1 is fine, because it shows the topography.

·         Page 6, Results: I think it would be nice for the authors to highlight the stations that are being discussed in the figures that are being referred to. In other words, in L219, the authors refer to station 5018, so it would be good for this station to be highlighted in Figure 3, as opposed to the reader constantly referring back to Figure 1. The authors could also do this for other stations like 5019, 5025, etc.

Minor suggestions:

·         Abstract, Line 9: Suggest changing "probably" to "likely". This does depend on the emission scenario, but according to the IPCC Sixth Assessment Report, there is a medium confidence (50% chance) that meteorological and hydrological droughts will increase in frequency and severity.

·         Abstract, L22: "the contrary happens…" I think for this part of the sentence, be more specific.

·         Page 1, L28: What kind of "Climate change simulations" are being referred to here?

·         P1, L35-37: Please provide the reader with a timeframe for each of these drought types (i.e., months, seasons, or years).

·         P1, L43: Should be "There are a plethora…".

·         P2, L52: Reading this sentence, particularly the part "temperature changes are considered" seems to be repeating the early part of the sentence. Please consider removing.

·         P2, L61: Could the authors provide some examples of other drought indices that do not include magnitude?

·         P2, L94: Please specify what the summer months are (i.e., June to August?).

·         P3, L97: How much precipitation does this region receive in these "higher-precipitation" months? Which months in particular? Please elaborate here.

·         P3, L99: Suggest change to "Regarding the orography".

·         P3, L108: As with the summer months, please indicate which months are being referred to here.

·         P3, L116: Suggest changing "needed" to "used".

·         P4, L125: The Penman-Monteith equation uses net radiation, soil heat flux and vapor pressure inputs. How do the authors calculate the potential ET from their three variables?

·         P4, L132: Out of interest, why do the SPREAD and SPETo datasets end in 2012? Have they been replaced?

·         P4, L148: How many stations were disregarded? This might be a good number to add in.

·         P5, L180: What is meant by "one-scale SSI"?

·         P5, L194: More information is needed on what "S-mode" is. It might not be familiar to all readers who have a vague understanding of PCA.

·         P7, Figure 3: The colors and shapes don't match between the plot and the legend. As in, the circle is blue in the legend, but green in the plot. Please fix.

·         P8, L254: Suggest changing "precipitations" to "precipitation events".

·         P8, L261-262: Why is the jump from 1 month to 2 months so large? Are there any other stations that show this type of behavior?

·         P9, Figure 5: The station 5026 maintains a high correlation well into 24 months. Any explanation as to why this is the case?

·         P9: Suggest putting in a new subsection heading, for example "PCA analysis".

·         P9, L273-275: So if my understanding is correct, the negative scores and loadings occur in PC2 for accumulation periods less than 5 months?

·         P10, "South"->"south".

·         P11, L316: "neither"->"either".

·         P11, L327: The authors might like to elaborate as to why there are gaps in the summer months.

·         P12 & P13: Suggest adding in the brief description about the crosses into the caption.

·         P14, L353: Is December when the first snow occurs over the region? Just trying to understand why this does not occur in January or February? Is it too dry?

·         P14, L368: This p-value matches the p-value in Table 1. Just wanting to confirm that this is correct.

·         P14, L370: Suggest change to "not statistically significant".

·         P16, L414: Suggest changing this to "…in December, precipitation increases".

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper studied the relationship between meteorological drought and hydrological drought in Guadalquivir River Basin, and specifically analyzed the characteristics of drought types linkage in 43 reservoir stations, which is important for water resources management in Guadalquivir River Basin. A few suggestions and questions：

S1: The structure and content of the data and methodology sections need to be adjusted and simplified again, and be noted not to be confused with the introduction section.

S2: The figures in the paper are not perfect, need to be revised. For example, the geographic location map in Figure 1 lacks scale and legend; and the curve map is not beautiful enough, etc.

Q1: The precipitation and evapotranspiration data are raster data, 5 km and 1.1 km respectively, how are they calculated at different scales, and how do SPEI and SSI match to analyze the relationship?

Q2: The relationship between meteorological drought and hydrological drought is influenced by topography, permeability and catchment area. What is the basis for the selection of influence factors? The basin is built with numerous reservoirs and is strongly influenced by human activities, why are the effects of human activities not considered?

There are also some comments in the manuscript of the article, please pay attention to check.

Comments for author File: Comments.zip

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Considering the given comments, the authors sufficiently improved the manuscript to warrant publication in Water.