| 06 Oct 2025
HYD-RESPONSES: daily hydro-meteorological catchment-level time series to analyse HYDrological drought dynamics in RESPONSE to (cumulative) water deficits in Swiss catchments
Abstract. The HYD-RESPONSES dataset (https://doi.org/10.5281/zenodo.14713274; von Matt et al., 2025) provides new daily catchment-level time series for key hydro-meteorological variables, including precipitation, snow water equivalent, temperature, soil moisture, (potential) evaporation, and streamflow. The dataset covers 184 small to large Swiss catchments of the surface water monitoring network operated by the Federal Office for the Environment (FOEN). The catchments range across a variety of streamflow regime types, mean altitudes, biogeographic regions, and anthropogenic influences. The data set provides daily average streamflow derived from measurements by the FOEN and daily hydrometeorological data (precipitation, temperature, radiation, snow and soil moisture) on the catchment level extracted from spatially gridded data provided by MeteoSwiss (RhiresD, TabsD, TmaxD, TminD, SrelD), MeteoSwiss and the WSL Institute for Snow and Avalanche Research SLF (SPASS), SLF (OSHD), and the European Centre for Medium-Range Weather Forecasts ECMWF (ERA5-Land).
In addition, derived indicators related to snowfall, snowmelt, (potential) water balance and streamflow are provided. Information on precipitation, evaporation-driven and streamflow deficits are provided in form of standardized and non-standardized (drought/deficit) indices. Standardized indices include the SPI, SPEI and SMRI and are provided on multiple aggregation scales from 1 to 24 months (mostly in 3-monthly steps). Non-standardized indices are provided as cumulative (water) deficits in (potential) water balance (CWD and PCWD) and streamflow (CQD). For all variables and indices, the climatology and the (standardized) anomalies are available on various time scales (daily, monthly, seasonal, and yearly). Drought event time series containing drought event numbers and drought event durations, are provided for streamflow droughts identified by using two percentile-based event definitions (fixed and variable threshold) and for cumulative water deficits (CWD, PCWD and CQD).
Detailed catchment descriptors covering hydro-climatological and hydro-terrestrial aspects as well as streamflow characteristics are provided for all catchments. The dataset can be used to study weather-driven streamflow extremes, to train data-driven machine-learning algorithms, to study drought propagation, and for comparative analyses of catchment responses in disturbed and undisturbed catchments. The dataset is compatible with the recently published CAMELS-CH dataset and with additional catchment descriptors provided by the FOEN.
This is a review for ESSD, von Matt et al., 2025: HYD-RESPONSES: daily hydro-meteorological catchment-level time series to analyse HYDrological drought dynamics in RESPONSE to (cumulative) water deficits in Swiss catchments
The described dataset appears to be of potential use, albeit limited for Switzerland-focused usage. I think the manuscript requires major revisions in terms of structure, motivation for certain choices or clearer descriptions as summarized in the general and the specific comments below.
General/major comments:
Item 1. The abstract and the introduction, while motivating and describing the dataset, do not lay out the logic of the manuscript. For example, the use cases in sec 6 come a bit as a surprise to the reader. In general, the manuscript would benefit from an additional verification effort, showing that the aggregation procedures work as they are intended. For example, 4.2.1: FOEN uses M7(Q), too, so there would be scope for a comparison.
Item 2. Description of catchments and respective coverage by the datasets (section 2-3, figure 1, 2, 3): Here, I think that a bit more care could be given to a comprehensible presentation:
Section 2 would benefit from clarifications i) that the catchments lie partially outside of CH, ii) whether they are fully disjunct (i.e. there is or there is no hierarchy in the catchments), and iii) that any altitude discussed here is basin average.
Then, in section 3.1, there is an explanation why certain stations are not used for the HYD-RESPONSES dataset; some items are self-explanatory, but others are not. Suggest to explain.
Section 3.2 starts a bit sloppy, as meteorological variables are indeed provided from multiple sources; suggest to re-phrase or re-organise this description. Which data does MeteoSwiss use for RhiresD in areas outside CH?
The very last sentence of section 3.2 explains that ERA5-Land data are aggregated to daily values, but does not provide details. Is it done in a way that makes respective data comparable to the other sources (TabsD, TminD, TmaxD, RhiresD)?
Fig 2 is somewhat unmotivated and only referenced in section 6.2.
Section 3.3 does not provide information on coverage outside of CH. This should be clarified. If restricted to CH, is this a problem for catchments with significant portions in neighbouring countries? L344 onwards and the discussion and conclusion sections in principle suggest so.
Item 3. The information around homogeneity/breakpoints is taken from elsewhere. Still, I think it is important to clearly explain their concepts (L189), because these are not self-explanatory terms. Their usage is also not quite clear. L213: what makes a breakpoint “significant”? Is it an ad hoc definition?
Item 4. Guidance on how to use the many different quantities in the dataset; the authors have compiled many different indices, deficit manifestions, etc, and their genesis and differences among related ones are explained well enough. However, what is missing is guidance for users which to use for which purpose. Some examples:
L245: Can the authors give context on whether the deficit remaining uncompensated over several years is realistic? They provide an extra quantity of annually reset deficits which indicates that it might not be. An expert user will probably know what to make of it, but less experienced users might be a bit lost.
Section 4.4: Which application would require the usage of SPI/SPEI/SMRI, respectively?
Section 4.6: fixed and variable threshold definition.
Section 5.2, L335: two BSI variants.
Item 5. The manuscript remains sometimes short when in comes to motivating certain choices or methods. For example:
L295: Why are more percentiles provided only for M7Q?
L309: purpose of “minor pooling”
I suggest to screen the manuscript for these instances and include respective explanations.
Item 6. Figures and references to figures. I think these must be clearly improved:
Figure 2 was mentioned in my item 2 already.
I find no reference to Figure 6 (although it might help explain the “phases” question that I put under “specific comments”).
Figure 7 should probably specify subfigures as (a) and (b).
Figure 9: Shouldn’t the caption specify *streamflow* drought for the pink and green shadings? I think what is missing here is the time series that was used for defining the drought periods. It seems related to panel j but not identical according to the text from L418 onwards. The y-axes should be labeled properly (T2m: [K], SWE: [mm], ...).
Figure 10: not referenced in the main text; the text supposed to discuss the figure mentions “pluvial inferieur”, which is not shown in Figure 10, several times around L470. What does the “n” stand for, catchments?
Specific comments:
L23/L89: please introduce CAMELS-CH to the uninformed user not only in section 8 but already at first mention/in the introduction.
L39/41: do the authors really mean “anthropogenic” in the sense of “caused by humans”? Or is it more about these events impacting the human “sphere” differently? Might also be relevant elsewhere (L375, L390).
L79: “as a result of non-transformation”, is this simply replicating the statement of “non-standardisation”? If so, recommend to delete.
Caption of Table 1: refer to glossary table in the appendix for variable names?
L230-233: The causality here is not entirely clear. I am guessing: The reset at sept 1st is a feature of SPASS SWE in order to avoid the “snow tower” feature. This feature leads to large snowmelt values in delta SWE. These large values are mitigated by the described interpolation. If so (or even if not), the chain could be spelled out more clearly.
L274: 50 implausible/missing values: Is this referring to the time series, or the distribution (i.e., before or after binning)?
L282: This means that values are capped at +-3 STD, which could be spelled out here. Can the authors briefly repeat the reasoning for this by Stagge et al. (2015) in this context?
L284: Please explain “standard time series”.
L299: “Q347” is only introduced in section 5.2; an explanation is necessary at the first instance, I think.
L305: What constitutes a “phase” as used throughout 4.7? Probably related to Figure 6 (unreferenced, see above). Unless this is clarified, it remains unclear what an “event” is.
Sub-Headings in section 5: “extraction of catchment descriptors (CD)”, “derivation of other CD”; these seem not very precise. What exactly is the difference between CD in 5.1 and 5.2? Can the header name or the distinction be specified?
L331: Is competing areal extent of several categories in a catchment the only possible constraint to representativeness? I could imagine that for example the spatial distribution in terms of upstream/downstream/margins could also be a factor.
L365: “partly on both monthly and yearly time scales”, this should be specified and motivated.
L383: The authors have provided a short interpretation of Fig 8; I think they should also do this for Figure A1 (which could also be moved from the appendix to the main part?).
L413: “lacking snowmelt”: wouldn’t there be more concrete evidence for this somewhere in the HYD-RESPONSES dataset?
L424: “Larger CWDs during...” is this a general (climatological) statement? The term “seasonal climatology” and the “(not shown)” addition might indicate this, but I recommend to stress this more clearly.
Starting sentence of Section 7: something is not quite right here with the references/model names.
Technical/editorial comments:
L9 onwards: inconsistent in naming all MeteoSwiss/SLF parameters, but only ERA5-Land as a whole.
L12, “information on precipitation, evaporation-driven and streamflow deficits”, can the authors please re-phrase; something seems not quite right here.
L93/94: “n=18/94” I think it is misleading as the n refers to streamflow regime types first and then to individual catchments; why not simply include the numbers in prose?
L203, “variables” should go after “flux”?
L264: suggest to unify reference to R packages across the manuscript. E.g., elsewhere it is “cwd R-package”, here it is “SCI-package”.
L284: There is a left-over bracket, probably to be closed after “3.2” in L285.
L293: I suggest to spell out the z score more clearly instead of the “(value-mu)/sigma terminology.
L308: “event definition”, drop “definition”?
L362: MAM = march april may as elsewhere? In general, it is not clear what the acronym(s) is/are supposed to say.
L383 An other > Another
L424: “actual” in the sense of “non-anomaly” or in the sense of “non-potential”? Same for L431.
L563 and elsewhere: data set or dataset?
L563: “alsop” typo