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Article: Environmental flow allocations in monsoonal Hong Kong

TitleEnvironmental flow allocations in monsoonal Hong Kong
Authors
KeywordsDischarge
Hydro-ecological relationships
Macroinvertebrates
Periphyton
Tropical streams
Issue Date2011
PublisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/FWB
Citation
Freshwater Biology, 2011, v. 56 n. 6, p. 1209-1230 How to Cite?
Abstract1.Hong Kong streams are subject to aggressive water extractions but the downstream water needs of ecosystems - i.e. environmental flow (e-flow) requirements - have not yet been addressed. This study investigated hydro-ecological relationships that could be used to establish e-flow allocations for streams in monsoonal Hong Kong. 2.Data were collected during the wet and dry seasons from 10 unpolluted streams experiencing a gradient of flow reductions (c. 0-98%). Relationships between flow conditions (percentage discharge reduction and absolute discharge volume) and responses of macroinvertebrate composition and periphyton condition were established for each season. 3.Declines in richness of Ephemeroptera and abundance of hydropsychid caddisflies, as well as increases in the proportion of predators, were linearly related to percentage discharge reduction during both seasons. Relationships were also recorded for eight other macroinvertebrate richness or compositional metrics during the dry season only. Relationships between macroinvertebrate assemblage attributes and absolute discharge volume across downstream reaches were also evident. Periphyton was relatively insensitive to flow reductions and did not provide useful hydro-ecological relationships, although declines in autotrophic index were related to percentage discharge reduction during the dry season. 4.Using hydro-ecological relationships established for macroinvertebrates, two levels of e-flow were proposed: a 'threshold' intended to maintain near-natural conditions and a 'degradation limit' that allowed no more than 25% of the maximum indicator response to flow reduction. Calculated threshold e-flows required downstream allocation of ≥74% of natural flows; degradation limit e-flows were ≥12% (wet) and ≥27% (dry). The discharge needed to maintain threshold conditions was 30-105Ls-1 (wet) and 5-14Ls-1 (dry), with degradation limit e-flows of 19-57Ls-1 (wet) and 3-6Ls-1 (dry), relative to natural mean discharges of 77-303Ls-1 (wet) and 3-18Ls-1 (dry). 5.The proposed e-flow allocations are indicative only, and significant obstacles to implementation have yet to be surmounted. Any such implementation requires monitoring of outcomes in order to refine the allocations and inform adaptive flow management for Hong Kong streams. © 2011 Blackwell Publishing Ltd.
Persistent Identifierhttp://hdl.handle.net/10722/140923
ISSN
2015 Impact Factor: 2.933
2015 SCImago Journal Rankings: 1.574
ISI Accession Number ID
Funding AgencyGrant Number
Research Grants Council of Hong Kong Special Administrative Region, China[HKU] 7509/06M
postgraduate studentship
Funding Information:

The work described in this paper was partially supported by a grant from the Research Grants Council of Hong Kong Special Administrative Region, China (Project No. [HKU] 7509/06M), and by a postgraduate studentship awarded to Sophia Q. Niu during her M.Phil. studies at the University of Hong Kong. We thank Jim Arrigoni for comments on an early draft, and Danny C. P. Lau and Kenneth M. Y. Leung for advice on statistical analyses; we are grateful also to Nancy E. Karraker, Aggie O.Y. Li and two anonymous reviewers for critical readings of the manuscript. Special thanks go to Lily C.Y. Ng for technical support.

References

 

DC FieldValueLanguage
dc.contributor.authorNiu, SQen_HK
dc.contributor.authorDudgeon, Den_HK
dc.date.accessioned2011-09-23T06:21:27Z-
dc.date.available2011-09-23T06:21:27Z-
dc.date.issued2011en_HK
dc.identifier.citationFreshwater Biology, 2011, v. 56 n. 6, p. 1209-1230en_HK
dc.identifier.issn0046-5070en_HK
dc.identifier.urihttp://hdl.handle.net/10722/140923-
dc.description.abstract1.Hong Kong streams are subject to aggressive water extractions but the downstream water needs of ecosystems - i.e. environmental flow (e-flow) requirements - have not yet been addressed. This study investigated hydro-ecological relationships that could be used to establish e-flow allocations for streams in monsoonal Hong Kong. 2.Data were collected during the wet and dry seasons from 10 unpolluted streams experiencing a gradient of flow reductions (c. 0-98%). Relationships between flow conditions (percentage discharge reduction and absolute discharge volume) and responses of macroinvertebrate composition and periphyton condition were established for each season. 3.Declines in richness of Ephemeroptera and abundance of hydropsychid caddisflies, as well as increases in the proportion of predators, were linearly related to percentage discharge reduction during both seasons. Relationships were also recorded for eight other macroinvertebrate richness or compositional metrics during the dry season only. Relationships between macroinvertebrate assemblage attributes and absolute discharge volume across downstream reaches were also evident. Periphyton was relatively insensitive to flow reductions and did not provide useful hydro-ecological relationships, although declines in autotrophic index were related to percentage discharge reduction during the dry season. 4.Using hydro-ecological relationships established for macroinvertebrates, two levels of e-flow were proposed: a 'threshold' intended to maintain near-natural conditions and a 'degradation limit' that allowed no more than 25% of the maximum indicator response to flow reduction. Calculated threshold e-flows required downstream allocation of ≥74% of natural flows; degradation limit e-flows were ≥12% (wet) and ≥27% (dry). The discharge needed to maintain threshold conditions was 30-105Ls-1 (wet) and 5-14Ls-1 (dry), with degradation limit e-flows of 19-57Ls-1 (wet) and 3-6Ls-1 (dry), relative to natural mean discharges of 77-303Ls-1 (wet) and 3-18Ls-1 (dry). 5.The proposed e-flow allocations are indicative only, and significant obstacles to implementation have yet to be surmounted. Any such implementation requires monitoring of outcomes in order to refine the allocations and inform adaptive flow management for Hong Kong streams. © 2011 Blackwell Publishing Ltd.en_HK
dc.languageengen_US
dc.publisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/FWBen_HK
dc.relation.ispartofFreshwater Biologyen_HK
dc.rightsThe definitive version is available at www.blackwell-synergy.com-
dc.subjectDischargeen_HK
dc.subjectHydro-ecological relationshipsen_HK
dc.subjectMacroinvertebratesen_HK
dc.subjectPeriphytonen_HK
dc.subjectTropical streamsen_HK
dc.titleEnvironmental flow allocations in monsoonal Hong Kongen_HK
dc.typeArticleen_HK
dc.identifier.emailDudgeon, D: ddudgeon@hku.hken_HK
dc.identifier.authorityDudgeon, D=rp00691en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1111/j.1365-2427.2010.02558.xen_HK
dc.identifier.scopuseid_2-s2.0-79954827804en_HK
dc.identifier.hkuros194869en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-79954827804&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume56en_HK
dc.identifier.issue6en_HK
dc.identifier.spage1209en_HK
dc.identifier.epage1230en_HK
dc.identifier.isiWOS:000289640800015-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridNiu, SQ=36671762700en_HK
dc.identifier.scopusauthoridDudgeon, D=7006559840en_HK
dc.identifier.citeulike9176171-

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