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Titolo:
Pool quality index: New method to define minimum flow requirements of high-gradient, low-order streams
Autore:
Azzellino, A; Vismara, R;
Indirizzi:
Univ Milan, Politecn Milan, DIIAR Dept Hydr Envir & Survey Engrg, Envir Div, I-20133 Milan, Italy Univ Milan Milan Italy I-20133 ey Engrg, Envir Div, I-20133 Milan, Italy
Titolo Testata:
JOURNAL OF ENVIRONMENTAL ENGINEERING-ASCE
fascicolo: 11, volume: 127, anno: 2001,
pagine: 1003 - 1013
SICI:
0733-9372(200111)127:11<1003:PQINMT>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
SUBSTRATUM COMPOSITION; MID-WALES; MACROINVERTEBRATE; PATTERNS; RIFFLES; RIVERS; FAUNA;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Engineering, Computing & Technology
Citazioni:
42
Recensione:
Indirizzi per estratti:
Indirizzo: Azzellino, A Univ Milan, Politecn Milan, DIIAR Dept Hydr Envir & Survey Engrg, Envir Div, Pza L da Vinci 32, I-20133 Milan, Italy Univ Milan Pza L daVinci 32 Milan Italy I-20133 ilan, Italy
Citazione:
A. Azzellino e R. Vismara, "Pool quality index: New method to define minimum flow requirements of high-gradient, low-order streams", J ENV ENG, 127(11), 2001, pp. 1003-1013

Abstract

High-gradient (>1%), low-order streams, characterized by hydraulically nonuniform and heterogeneous channels, represent a problem for the most widelyemployed habitat-based in-stream flow methods (IFIM-PHABSIM). In a nonuniform high gradient and turbulent channel, as low-order streams usually are, the classical 1 D hydraulic modeling, ordinarily employed by in-stream flowmodels to simulate the changes in fish habitat with the flow, could be questionable, if not completely inapplicable. Channel morphology in fact playsa major role in association with hydraulics in determining the abiotic environments (biotopes) in which aquatic communities live. Particularly, in low-order river systems, different channel form features shape the biologicalcommunity that can be hosted in a certain biotope. For this reason, the link between morphology and discharge is important when evaluating possible impacts of flow reduction on aquatic organisms. To represent the relationship between hydraulics and channel morphology quantitatively, a hydraulic diversity concept has been adopted. Studies from the literature have revealed that, in a regulated river, a decrease of the environmental variability including hydraulic diversity quite often resulted in a downstream decrease ofthe macro-invertebrate diversity, which can consequently affect fish biomass. These considerations create the ground for a hydraulic diversity-discharge-based in-stream flow method with the aim to promote high community diversity in a low-order regulated stream. A statistic ordination technique (correspondence analysis) applied to 370 hydraulic sections helped to identifyfour main morphological units (pools, deep pools, and slow and fast riffles) in terms of hydraulic diversity. In each morphological unit, the hydraulic diversity-discharge relationship was investigated and modeled by means of best-fit regression curves. Combining the hydraulic diversity-discharge curves from different morphological units (pools and riffles), a simplified model of the stream [pool quality index (PQI)] was obtained. This model hasbeen applied to make recommendations for the minimum flow requirements in six low-order river sites. PQI recommendations were consistent with hydrology and other hydrology-based instream flow methodologies. Finally, a multiple regression model indicated that in 12 low-order stream sites a good dealof the variability of macro-invertebrate diversity is explained by the availability of hydraulic environments modeled by means of PQI curves. In conclusion, given the encouraging cues about the ecological meaning of PQI and the possibility to overcome difficulties typically encountered by other methods in the low-order river modeling, PQI can be considered a valid alternative for assessing the in-stream flow needs of low-order streams.

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Documento generato il 30/11/20 alle ore 14:52:36