the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 15 Nov 2024
Hydrological regime index for non-perennial rivers
Abstract. The hydrological regime is an integrated basin response that constitutes an established paradigm for environmental flows (E-Flows) to mimic it since all its components influence aquatic life, and therefore fluvial ecosystems. It has been widely described that human activities and climate change modify the natural hydrological regime. These changes in non-permanent rivers generally tend towards greater intermittency, a condition that limits the applicability of hydrological alteration indices. The general aim of the paper was to develop an aggregated impact index, the Hydrological Regime Index (HRI) suitable for flow alteration assessment in non-permanent rivers. The HRI is composed of the flow magnitude attenuation, timing of maximum flow and interannual flow variation impact factors. The HRI is based on simple conceptualisations and uses monthly flow data, allowing its applicability in basins with limited information. The HRI was suitable to evaluate the impacts on the river regime of both the Desaguadero-Salado-Chadiluevú-Curacó River which is severely dammed with intermit runoff and the Colorado River with permanent runoff. In all the cases, the HRI was able to discriminate different impacts on the hydrological regime for natural, low and high impoundment conditions. Thus, the HRI constitutes a very useful tool for determining E-Flows and quantifying impacts due to water or land use changes.
- Preprint
(1401 KB) - Metadata XML
- BibTeX
- EndNote
Status: final response (author comments only)
-
RC1: 'Comment on hess-2024-338', Anonymous Referee #1, 18 Dec 2024
Overall, this research article presents a useful index to evaluate flow regime alteration. The paper is well written and well illustrated. I support the acceptance of the work as is.
Citation: https://doi.org/10.5194/hess-2024-338-RC1 -
RC2: 'Comment on hess-2024-338', Anonymous Referee #2, 30 Dec 2024
Major Comments
In this study, the authors develop a single, comprehensive index to quantify the hydrologic regime in the DSCC River basin of Argentina. This metric, the Hydrological Regime Index, is useful in that it quantifies alterations in flow magnitude, timing, and variation. The development of this metric was motivated by the inability of existing metrics to quantify hydrologic regimes of non-permanent rivers.
While I think the authors make a fair argument that this type of metric would be useful, I don’t believe that the authors communicate well enough what about their new metric makes it more useful than other metrics for non-permanent rivers. In other words, I think the authors need to better communicate the existing ‘gap’ in the research and how this metric addresses that gap. This is especially apparent in the discussion section, where there is minimal discussion of non-permanent rivers.
Another weakness of the manuscript is the organization. The exception is the results, where the authors do a good job of walking through the results at the different types of gages where the metric was calculated and explaining why the findings make sense and are important. This manuscript could be improved if the authors had set up these expectations earlier, likely in the introduction. For example, a paragraph that explains what the authors expect a useful metric of hydrologic alteration to capture at each of the gages included in the analysis would help readers assess the results. Additionally, this would also allow the authors to refer to these expectations throughout the manuscript and eventually assess whether the Hydrological Regime Index met these expectations. I believe this would add a lot of much needed structure to the manuscript. As written, the methods section reads like the metric has been applied to many different gages for no clear reason. Making this change would help readers understand why each analysis is being done.
Finally, the terminology used throughout this manuscript tends to overcomplicate things, or even be slightly (unintentionally) misleading. Consider replacing the ‘natural’ vs. ‘modified’ language with ‘upstream’ vs. ‘downstream’. In theory, you don’t know if and how modified the flow downstream of a dam is until the analysis is completed. Additionally, flow upstream of dams is likely also modified by other factors. Also consider replacing what you call ‘actual’ with terminology like ‘current’ or ‘present’. Even historical flow is ‘actual’, in that they are real, observed values. Using ‘current’ or ‘present’ sets up a better contrast with ‘historical’. It’s also never very clear to me what ‘low impoundment’ vs ‘high impoundment’ conditions means.
Minor Comments
Introduction
A lot of this section discusses the topic of connectivity, but that’s not relevant to the rest of this paper. Connectivity and hydrologic alteration are not the same, and the metric introduced in this paper does not measure connectivity. Consider removing most, if not all, mentions of connectivity.
Line 27: “In large basins, the headwaters of the drainage network are generally located in a mountainous sector that favours the occurrence of precipitation due to the orographic effect”. Is this true? A lot of large basins don’t contain mountains. Reference needed.
Lines 29- 31: Need to include references for these statements.
Lines 58-60: “Indeed, indices based only on flow statistics…fail when no flow conditions are present”. Reference needed. What is meant by ‘fail’? These metrics can still be calculated when streamflow is equal to 0. This is the major gap you’re working to address. I would like to see more evidence that this statement is true. Please expand more on how exactly other metrics fail and provide some examples.
Line 62: This is the first mention of the DSCC River. Consider adding some more information, like the country where it’s located, to help orient the reader.
Study Area
There’s a lot of information provided here in the text, tables, and figure. So much so that it becomes difficult to understand what is important because parts of this section aren’t well organized. One example: the paragraphs that start at lines 137 and 161 both talk about El Nino, but the paragraph starting at 161 isn’t really about El Nino, it seems. Consider finding ways to make the information provided in this section more concise and more organized to help the reader understand what’s important.
Line 84: What is meant by “fully developed”? Could you just say “Argentina” instead of “Argentine territory” to improve clarity?
Line 90: Is the Cordillera de los Andes the same as the Andes mountain range (line 86)? If so, change so that you’re using the same name to refer the range throughout.
Line 96: The precipitation doesn’t contribute to the hydrology? Can that be true? The opposite is said in line 122.
Line 100: “and the MZ River through the last one”. Unclear what this means.
Table 1: Why are there multiple mean annual discharge and record period values for some gauges? Historical vs. actual and modified vs. natural haven’t been defined yet, so this table is really difficult to understand at this point. After a read through, I’m not convinced this table is necessary. The later tables about the gauges that are actually analyzed seem more useful.
Line 148: “…irrigation demands are unusually high”. Reference needed.
Paragraph at line 161: It’s not clear what this paragraph is about. Reorganize or incorporate the relevant information into other paragraphs.
Paragraph at line 179: You’ve said most of this information in other parts of this section. You also introduce the topic of salinization here, which isn’t relevant to this manuscript. Consider cutting.
Figure 3: It still hasn’t been said anywhere what defines historical vs. actual flows or natural vs. modified regime. Without that information, it’s not clear what this figure is trying to communicate to the reader.
Materials and methods
Line 195: “…which is by definition the hydrologic regime”. Not necessarily – you can characterize flow regime at finer or coarser temporal scales. Edit for clarity.
Line 226: definitions of TQmN.max and TQmM.max are unclear – what is meant by ‘number of months’?
Line 230: Could you add a sentence somewhere to clarify what 0.0833 means in this equation? Why 0.0833 and not a different number?
Line 239: Is Qsm always going to be equal to or greater than 8.33? If so, is it necessary to take the absolute value in eq. 8, since it should always be positive?
Table 4: CAA is mentioned as an upstream gage in the table, but not in the text (Line 275); Do we need this table in addition to table 1? Or could they be combined? I’m also wondering if it would be useful/possible to label the gages (highlight in a different color) that are used in the analysis in either Figure 1 or 2 – not necessary, just a thought.
Paragraph at line 285: This is a difficult paragraph to follow. Edit to improve clarity.
Results
This section is well organized. If the methods followed the structure of this section, organization and readability would be improved.
Paragraph at line 414, and elsewhere: There is a lot of explaining and providing contextual information in the results section. I think this is relevant information, but I’m not sure the results section is the right place for it. Maybe this would fit better in the methods or in the discussion?
Discussion
Line 549: Here and elsewhere, the authors claim that HRI is able to quantify the spatial impacts on the flow regime, but based on my reading, this is not true. No spatial analysis is incorporated into this metric. Please edit to clarify.
Line 600, elsewhere: The authors say that HRI is a useful tool for defining E-Flows, but it is not clear how HRI would be useful in this context. Please expand on exactly how HRI could be used to define e-flows.
Line 603: This paragraph feels disconnected from the rest. Please consider either removing, or expanding to better integrate it.
Technical
Line 87: Change ‘partial’ to ‘partially’
Line 101: Change “till” to “until”
Line 103: I believe you mean “aforementioned”, not “forehead”.
198: Change “similarly” to “similar”
203: typo
You use different phrases when referring to no-flow events (no flow, non-flow). Consider standardizing the language used.
Citation: https://doi.org/10.5194/hess-2024-338-RC2
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 179 | 31 | 9 | 219 | 4 | 4 |
- HTML: 179
- PDF: 31
- XML: 9
- Total: 219
- BibTeX: 4
- EndNote: 4
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1