Rivers – Data collection activities

INHABIT project

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Rivers – Data collection activities

Rivers – Macroinvertebrates sampling

Macroinvertebrate sampling is performed through a multihabitat technique. Sample units are collected proportionally to presence of microhabitats. Each sample is formed by a defined number of units (e.g. 10) collected in all present habitat with a minimum percentage (multihabitat proportional).
Details of the sampling technique can be found here or in Notiziario IRSA Marzo 2007 (in Italian).
For the aims of INHABIT project, some specific adaptations have been included to the macroinvertebrates sampling and identification procedure, specifically:

  • In each of the sampling stations in Sardinia 20 sampling units have been collected, 10 in riffle area and 10 in pool area, instead of the sole 10 units in pool area mandatory for HER21 (Sardinia) for operational monitoring.
  • In most of the sampling stations in Piedmont HER01 (Western Alps) 20 sampling units have been collected, 10 as ‘generic’ sample - with riffle characteristics - and 10 as ‘generic’ sample - with pool characteristics -, instead of the mandatory 10 ‘generic’ units for HER01 operational monitoring. In the same way, in most of the sampling stations Piedmont HER06 two generic samplings have been collected in two adjacent areas, 10 sampling units each.
  • In all sampling stations, whichever the region, all sampling units have been kept separate. In each site 10 or (in most cases) 20 units have been sampled, each associated to a specific microhabitat and characterized by values of current velocity, water depth and flow type.
  • Identification has been undertaken to family level, although detail identification has been performed for selected taxa (e.g. Ephemeroptera).

Rivers – Nutrients retention measure

Experiments for nutrient retention measure has been carried out by means of short term nutrient addition, involving the addition of concentrate solution of NH4 e PO4 at a constant rate. Detailed description of the procedure is available in Italian in Deliverable Pd4.

River stretch selection criteria
River stretches have been selected according to the following criteria:

  • stream order 1-3, discharge < 300 l/s, single channel;
  • water bodies covering a gradient of morphological alteration.

Habitat and chemico-physical characterization
Characterization of river reaches has been performed by means of:

  • discharge measurement (with velocimeter);
  • wetted channel width and depth measurement;
  • flow type and substrate type recording;
  • chemico-physical variables measurement (N-NO3, N-NH4, P-PO4, Cl, SO4, Ca, Mg, Na, K, water temperature and conductivity);
  • characterization of hyporheic environment (conductivity, and temperature of surface and hyporheic water, measure of hydraulic vertical gradient);
  • habitat survey through CARAVAGGIO method;
  • benthic fauna and diatoms sampling (in most of the sites).

Nutrient addition
Experiments for nutrient retention has been carried out by means of short term nutrient addition. Nutrients, i.e. ammonium and orthophosphate as, respectively, NH4Cl and Na(H2PO4)*H2O, have been added to the stream simultaneously with a conservative tracer, i.e. chloride (NaCl) at a constant flow rate.  
Variation in concentration of the conservative tracer are recorded downstream the addition point, generally to a distance of 100m, through a data logger allowing the measure of conductivity every 5-10 seconds along the duration of the experiment. The nutrient addition experiment area is partly overlapping, or adjoining, the sampling area for biological communities (invertebrates and diatoms). At every station a set of morphological and hydrological features have been recorded, including: water and total channel width, water depth at left, center and right side of the channel, substrate and flow types, presence of mesohabitat riffle, pool or generic.
At each sampling point, where substrate was suitable, mini-piezometers have been installed in order to improve hydrological characterization of hyporheic. Measures of conductivity and surface and hyporheic temperature have been taken and vertical hydraulic gradient has been estimated.

Nutrient addition

Operational scheme of field activities for nutrient addition experiment
Photo gallery

Rivers – Diatoms sampling

Diatoms are sampled from mineral substrates. Ideal substrates are pebbles, sized between 6 and 20cm along the intermediate axis (mesolithal). A variable number of stones are collected in an area of the wetted channel having all following characteristics:

  • Location In riffle area (or at least an area of appreciable water velocity, as general rule above 20 cm/s).
  • Sufficient water depth to fully cover the substrate;  at the same time water should be shallow enough to ensure the collection of diatoms in the euphotic zone.
  • Lack of deep shading.
    Stones are brushed with a toothbrush for an overall surface of 100cm2. Collected material is rinsed together with the toothbrush in a shallow tray and transferred into a 50-100ml vial for preservation.
    Photo gallery

Rivers – Information on habitat and local hydromorphology (RES I1 – HABITAT INFORMATION)

Habitat and local hydromorphological characterization of river reaches have been performed by means of CARAVAGGIO method. The survey is undertaken along a 500m stretch located for the most part upstream of the biological sampling site. The method allows the recording of specific stream and banks habitat features on a 500m stretch along the river. The following portions of the stream are considered: channel, banks and peri-fluvial areas. The method is divided into two separate parts. In the first one, bank and channel features are recorded every 50m on 10 equally spaced spot-checks perpendicular to river flows. In the second section, or sweep-up, features are recorded along the whole 500m stretch.

The characterization of the reach can be performed either considering the single distinct recorded features or through a set of descriptors (described in details in deliverable Pd3, in Italian), each considering a peculiar aspects of stream habitat:

  • Habitat Modification Score (HMS): level of morphological alteration caused by artificial structures;
  • Habitat Quality Assessment (HQA): diversification and quality of channel and bank habitat;
  • Land Use Index (LUIr): level of anthropization of land use in stream and riparian areas;
  • Habitat Quality Index (Italian acronym: IQH): mean EQR value of the three previous indices;
  • Lentic-lotic River Descriptor (LRD): definition of lentic-lotic character in a stream reach.

An important activity of the INHABIT project in the development of CARAVAGGIO method has been dedicated to the definition and verification of class boundaries for the indices included in the calculation of IQH (Habitat Quality Index), for habitat classification of the river reach under the DM 260/2010 (Italian legislation). Defined class boundaries for the single descriptors allow the classification according to different aspects of stream habitat. Tables containing class boundaries are here reported, as partly presented in deliverable Pd3. An update of class boundaries for LUIr index following data analyses performed after deliverable Pd3 has been made. New values are reported in the following table.

Tab. 1 – Descriptors of HMS index from CARAVAGGIO surveys (Reference sites: n=87; siti non reference sites: n= 273).

On the basis of the data reported in Table 1 a boundary for the definition of HMS high status for rivers has been set  (Table 2). The boundary is set as the 90th percentiles of values observed in reference sites.

Tab. 2 – High status definition according to HMS index, according to 2000/60/EC.

Tab. 3 – Quality classes according to HMS index, to be used for biological data interpretation.

Tab. 4 – High status definition according to LUIr index, under the 2000/60/EC.

Tab. 5 – Quality classes according to LUIr index, to be used for biological data interpretation

Tab. 6 (a-e) – Definition of high status quality according to HQA index, under the 2000/60/EC, and class boundaries. 

Tab. 6 (f) - Definition of high status quality according to HQA index, for streams not included in the previous tables, under the 2000/60/EC, and class boundaries (median HQA ref 57).

Tab. 7a – Habitat quality status for temporary streams and small – very small lowland streams.

Tab. 7b -  Habitat quality status for other streams.

Tab. 8 – Classification of overall hydromorphological status, when habitat information is evaluated.

A brief description of CARAVAGGIO method and derived descriptor is available here.
Field form and application keys are available here.
The Guide to survey and description of river habitats (Manual of CARAVAGGIO method – Italian version) will be available soon.