CNR-IRSA activities related to INHABIT

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Pool & Riffle

Sampling procedure is based on habitat evaluation of the site. As first step identification of a riffle-pool sequence is required (if present). For operational monitoring sampling is performed in only one of the two areas, although in specific cases sample collection from both mesohabitats can be appropriate. Selection of pool or riffle area depends on stream type. Recognition of riffle/pool sequence is based on identification of adjacent areas characterized by comparatively different turbulence, depth, substrate size and erosional/depositional features. Pool areas show generally limited turbulence and finer substrate size compared to riffle and are characterized predominantly by depositional features. It can be considered as a lentic area, although it is not necessarily a no-perceptible flow area. Riffle areas present typically erosional features, showing generally shallower depth and higher turbulence if compared to pools and can generally be considered as a lotic section. Key aspect in riffle/pool identification is the comparison between two adjacent areas showing different flow characteristics.
In given stream types identification of a clear riffle /pool sequence can be awkward. This is the case for instance of mountain streams in alpine areas, where a ‘step-pool’ sequence can be frequently observed, or in small lowland streams, where discharge variations are limited and uniform substrate and flow type are typically present. When it is not possible to clearly recognize a riffle/pool sequence, quantification of microhabitats (and consequent allocation of sampling units) is performed independently from the two areas in a representative stretch. In such circumstance we refer to a ‘generic’ sampling.

Fiume Aniene – Jenne (Lazio, RM).
Mesohabitat riffle (sinistra) e pool (destra), HER 13
Torrente Sizzone – Maggiora (Piemonte, NO - progetto INHABIT).
Campionamento ‘generico’, Piccoli fiumi della HER 6.