Page 101 - Freshwater-Biology-and-Ecology-Handbook

Geochemistry One of either alkalinity (preferred but requires laboratory analysis), hardness, calcium concentration
or electrical conductivity

Estimate of surface velocity in the main flow, optional if an estimate of discharge category is not
Velocity category
available

These parameters should be recorded with every biological sample. If the samples are to be analysed with RIVPACS, it may
be necessary to collect these environmental measurements in other seasons in order to determine the annual averages that
RIVPACS needs.

Table 2.5 Table 2.6
Surface velocity categories used by RIVPACS Discharge categories used by RIVPACS
Current velocity
Velocity category Discharge category Mean annual discharge
(metres per second)
1 ≤ 10 1 < 0.31

2 > 10–25 2 0.31–0.62

3 > 25–50 3 0.62–1.25
4 > 50–100 4 1.25–2.50
5 > 100 5 2.50–5.00

6 5.00–10.00
7 10.00–20.00
RIVPACS also requires environmental data collected from
maps, originally 1:50 000 Ordnance Survey, but now more 8 20.00–40.00
commonly from GIS systems at similar scale:
9 40.00–80.00
10 > 80.00

Ordnance Survey grid reference
Altitude

Distance from source – (the furthest source along the
longest tributary from the site)
Slope

Discharge category – from maps or hydrological systems

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