Minimum acceptable flow measurement

BACKGROUND

Minimum acceptable flow is the minimum flow rate to be maintained in a water course perpendicular to a structure to preserve biological balance and water usage downstream. Consequently, sampling authorisations are limited. Minimum acceptable flow is not a hydrological concept; it is a regulatory requirement in Europe.

DESCRIPTION OF THE APPLICATION

To meet this regulatory requirement, we were asked to install a flow meter on the Vire River, slightly upstream of the “La Maugeautière” pumping station. The water course at this point is around 7 to 8m wide. During low water periods, the depth of the water barely exceeds 30cm. Furthermore, the only available place to install the flow meter is located just after a large bend.

EQUIPMENT USED

FLOW METER
Uf 322 CO converter SM 1527 wetted probes
Débitmètre Uf 322 CO RV Sonde mouillée SM 1527
This is an instrument (fixed terminal) that is no longer sold by Ultraflux.
The recent devices Uf 811 CO, Uf 821 CO and Uf 831 CO could also be used for the type of application described.
They make it possible to create two interwoven measurement chords.
Their clever installation means that they are well protected and require little maintenance.

The equipment is completed with a pressure level measuring device.

RESULTS

Accurate and continuous measurement, as expected by our client.

ADVANTAGES

Here, the ultrasound transit time flow measurement means that:

  • The full measurement scope can be covered, from low to high water levels,
  • Reliable and mean measurements can be taken across the entire length of the chord, even though the velocity profile is not stable during low water periods.