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Wastewater flow monitoring is conducted for many reasons, whether it be as part of an I&I assessment or a full calibration for a hydraulic model, AML can provide solutions utilising different monitoring methodologies.  The most common methodologies are:


HVQ – Height, Velocity, Quantity

In-pipe HVQ flow monitors are best utilised in pipes that are larger than 225mm diameter, where the minimum flow depth is greater than 50mm and flow velocity is greater than 0.2m/s.  Area velocity methods can have marginal accuracy uncertainty for the lower flow rate conditions and if utilised for these conditions they should be highly calibrated and confirmed in the lower flow ranges.


AML provide and use flow monitors that measure average velocity and should only require minor velocity adjustment factors applied to the raw data.  These factors are “site specific” and are dependent on the hydraulics.


Calibration of the velocity, depth and quantity readings are conducted throughout the agreed monitoring periods.  Velocity calibration is undertaken utilising accepted point profiling techniques as applicable to the flow conditions and relevant ISO standards.

V-Notch Weir

V-notch weirs are best utilised in smaller catchments (i.e., less than 5 to 10km of public sewer) for very accurate flow measurements.  They are installed with a depth sensor and a velocity sensor.  The velocity sensor is installed in the inlet pipe to provide an estimate of flows should the weir structure become surcharged.  The velocity is cross checked with the free flow weir quantities to confirm the accuracy where possible.


AML can provide temporary flumes for smaller pipes which are better utilised in smaller catchments (i.e., less than 2.5km of public sewer) where lower anticipated flow rates are expected.  Flumes can be installed with a velocity sensor in the inlet pipe to measure flows should the flume structure become surcharged.  The quantity from the velocity sensor is always cross checked with the free flow flume quantities to confirm the accuracy of the gauging site when possible.

Overflow Monitoring Methodology

AML can provide several types of overflow monitoring methodology depending on required outcomes.  These are as follows:

  • Simple manual visual indicators (e.g., sand, corks, float sticks)

  • Switch indicators connected to event loggers

  • Ultrasonic level sensors and data loggers

  • HVQ flow monitors – installed either in the main line or in the dry overflow pipe

Rain Gauge Methodology

AML use 0.2mm tipping bucket rain gauges manufactured by Hydrological Services Ltd in Sydney Australia.  Tipping buckets are mounted on three adjustable mounting pins to allow the tipping bucket to be levelled.  Rain gauge tips are recorded using a compact waterproof rain gauge event logger to minimise the size of the rain gauge installation.  


Rainfall Time, Duration and Intensity information can be analysed from the recorded information.  Rain gauges are secured to the mounting location to ensure they do not fall over during high winds.

Pump Station Data Analysis Methodology

Pump Station discharge monitoring can be conducted by means of recording the pump status (i.e., pump on / off) or the stations electronic flow meter.  In addition, AML can also provide wetwell level monitoring.


As part of Pump Station monitoring AML can also conduct pump drawdown testing.  This involves wetwell dimensional survey, running each pump and pump combination.  AML will then provide all test results and findings.


AML can also provide ultrasonic flow meters which can be installed on the discharge main if appropriate pipe lengths are available.  These can either be installed as a temporary installation or a permanent solution.  Note: for some older Concrete Lined Steel pipes, clamp-on meters may not work. 


AML request the attendance of the principal’s electrician to assist with the installation of all equipment at pump stations to ensure safety of personnel and security of the system



AML can also provide the following services to meet your needs:


  • Site investigations and recommendations.

  • Inflow and Infiltration investigations

  • Smoke testing of public and domestic sanitary systems.

  • Visual manhole and property inspections, flow isolation, dye testing.

  • Combined Sewer – Stormwater Overflow investigations.

  • On site calibration and auditing of permanent or temporary flow meters.

  • Installations of long- and short-term monitoring systems.

  • Manhole assets data collection

  • Installation of event notification systems

  • Catchment management planning.

  • Desktop data auditing and evaluation.

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