Assessment of hydrological pathways in East African montane catchments under different land use

Jacobs, Suzanne R.; Timbe, Edison; Weeser, Björn; Rufino, Mariana C.; Butterbach-Bahl, Klaus; Breuer, Lutz

doi:https://doi.org/10.5194/hess-22-4981-2018

Articles | Volume 22, issue 9

https://doi.org/10.5194/hess-22-4981-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-22-4981-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 22, issue 9

Research article

|

27 Sep 2018

Research article |

| 27 Sep 2018

Assessment of hydrological pathways in East African montane catchments under different land use

Suzanne R. Jacobs, Edison Timbe, Björn Weeser, Mariana C. Rufino, Klaus Butterbach-Bahl, and Lutz Breuer

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Final revised paper (published on 27 Sep 2018)
Supplement to the final revised paper
Preprint (discussion started on 13 Feb 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Interactive comment on "Land use alters dominant water sources and flow paths in tropical montane catchments in East Africa"', Anonymous Referee #1, 06 Mar 2018
- AC1: 'Response to major comments of Reviewer #1', Suzanne Jacobs, 04 Apr 2018
RC2: 'Review', Anonymous Referee #2, 13 Mar 2018
- AC2: 'Response to major comments of Reviewer #2', Suzanne Jacobs, 08 Apr 2018
RC3: 'Review comments on hess-2018-61', Anonymous Referee #3, 19 Mar 2018
- AC3: 'Response to major comments of Reviewer #3', Suzanne Jacobs, 08 Apr 2018
RC4: 'Review', Anonymous Referee #4, 20 Mar 2018
- AC4: 'Response to major comments of Reviewer #4', Suzanne Jacobs, 08 Apr 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) (19 Apr 2018) by Markus Hrachowitz

AR by Suzanne Jacobs on behalf of the Authors (29 May 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (07 Jun 2018) by Markus Hrachowitz

RR by Anonymous Referee #2 (11 Jun 2018)

RR by Anonymous Referee #3 (25 Jul 2018)

Suggestions for revision or reasons for rejection

The authors have addressed all of my comments in detail and implemented the changes into the manuscript. The high uncertainties of the MTT’s were presented more clearly and the discussion of the results was adapted accordingly.
There is only one more issue I would like the authors to address:
In Sect. 3.3 (P9, L18-19), the authors summarize the results of the end-member mixing analysis: “The EMMA resulted in a dominant contribution of precipitation (PC) in NF (median: 46.4, 95 % confidence interval: 30.5–54.4 %) and SHA (57.4, 45.3–78.6 %), while spring water (TTP-SP.a) dominated in TTP (55.6, 45.3–70.7 %) (Fig. 5).”. In contrast, the transit time modeling and the young water fractions suggests the opposite for NF and SHA (Sect. 4.3, P12, L25): “However, the long estimated MTTs and the low fraction of young water (YWF) suggest that the majority stream water in all catchments originates from ‘old’ water or groundwater.”. At the end of this paragraph, the authors point out that (P12, L30-31): “The importance of groundwater does, however, contradict the generally high contribution of precipitation and throughfall to streamflow in most catchments.”. However, an explanation for these opposite results is missing here. Instead, the section continues to discuss the MTT’s of soil water. Only later in Sect. 4.4 the authors point towards the large uncertainties in the EMMA, as well as to the uncertainties in the transit time models, without clearly indicating which result of their two analysis methods is (if at all) the most reliable. As a consequence, the reader might be left puzzled about the validity of the presented results as well as the conclusions drawn from them (i.e., flow processes). I would therefore encourage the authors to discuss the opposite results for NF and SHA more thoroughly.

Minor comments:
P11, L28-30: “The end member mixing analysis (EMMA) showed that precipitation (PC) was one of the three selected end members in all catchments, as depicted in our conceptual model of the rainfall–runoff generation processes in the three sub-catchments with different land use (Fig. 6).” This is not logical: you select PC as an end-member in the EMMA and then present this selection of PC a s a result? Do you mean instead that “precipitation (PC) was the dominant contribution in streamflow in all catchments”?
P11, L32: Include “high” before “hydraulic conductivity”
P12, L15: “The latter…” Use “This” instead, since only one end-member is mentioned in the previous sentence.

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RR by Anonymous Referee #1 (13 Aug 2018)

ED: Publish subject to minor revisions (review by editor) (28 Aug 2018) by Markus Hrachowitz

AR by Suzanne Jacobs on behalf of the Authors (06 Sep 2018) Author's response Manuscript

ED: Publish subject to technical corrections (07 Sep 2018) by Markus Hrachowitz

AR by Suzanne Jacobs on behalf of the Authors (11 Sep 2018) Author's response Manuscript

Short summary

This study investigated how land use affects stream water sources and flow paths in an East African tropical montane area. Rainfall was identified as an important stream water source in the forest and smallholder agriculture sub-catchments, while springs were more important in the commercial tea plantation sub-catchment. However, 15 % or less of the stream water consisted of water with an age of less than 3 months, indicating that groundwater plays an important role in all land use types.