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| Titel |
Defining environmental flows requirements at regional scale by using meso-scale habitat models and catchments classification |
| VerfasserIn |
Paolo Vezza, Claudio Comoglio, Maurizio Rosso |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036250
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| Zusammenfassung |
| The alterations of the natural flow regime and in-stream channel modification due to
abstraction from watercourses act on biota through an hydraulic template, which is mediated
by channel morphology. Modeling channel hydro-morphology is needed in order to
evaluate how much habitat is available for selected fauna under specific environmental
conditions, and consequently to assist decision makers in planning options for regulated
river management. Meso-scale habitat modeling methods (e.g., MesoHABSIM)
offer advantages over the traditional physical habitat evaluation, involving a larger
range of habitat variables, allowing longer length of surveyed rivers and enabling
understanding of fish behavior at larger spatial scale. In this study we defined a
bottom-up method for the ecological discharge evaluation at regional scale, focusing on
catchments smaller than 50 km2, most of them located within mountainous areas of
Apennines and Alps mountain range in Piedmont (NW Italy). Within the regional study
domain we identified 30 representative catchments not affected by water abstractions
in order to build up the habitat-flow relationship, to be used as reference when
evaluating regulated watercourses or new projects. For each stream we chose a
representative reach and obtained fish data by sampling every single functional
habitat (i.e. meso-habitat) within the site, keeping separated each area by using
nets. The target species were brown trout (Salmo trutta), marble trout (Salmo trutta
marmoratus), bullhead (Cottus gobius), chub (Leuciscus cephalus), barbel (Barbus barbus),
vairone (Leuciscus souffia) and other rheophilic Cyprinids. The fish habitat suitability
criteria was obtained from the observation of habitat use by a selected organism
described with a multivariate relationship between habitat characteristics and fish
presence. Habitat type, mean slope, cover, biotic choriotop and substrate, stream
depth and velocity, water pH, temperature and percentage of dissolved oxygen
were collected for each sampled area and considered as independent variables.
According to the MesoHABSIM method, we performed a stepwise forward logistic
regression in order to build up a biological model identifying the habitat characteristics
mostly used by a target fish. For each stream we predicted changes in habitat area
over a range of discharges by building the habitat-flow rating curves. Finally, in
order to define a regional criteria needed to fulfill environmental flow requirements,
we split the study domain according to the regression tree classification criterion
defining homogenous sub-regions distinct on both environmental flows and catchment
characteristics. |
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