Max Oulton National Centre for Environmental Information NIWA’s Cascade flume makes open-channel water flow measurement as easy as it gets Weirs and flumes are useful for flow measurement, but… For open-channel water metering you need the right design to avoid: • loss of flow from backwater, or flooding and overflowing upstream • errors due to blockage by weed, debris and silt • poor accuracy: not meeting the +/-10% requirement • not measuring the full range of flows. The benefits of NIWA’s Cascade flume A Cascade flume, when properly installed, will solve these problems for its recommended flow range. Practical benefits • needs little maintenance – passes debris and sediment • suitable for sites with little fall (unlike a weir) • greatly simplifies flow-rate measurement • inexpensive – from purchase, through installation to ‘old age’ • easy to handle – plastic-moulded in one piece, lightweight (68kg) • easy to install – dig in, level, retain with concrete (0.55m3), mix on site. Compliance benefits • complies with current flow consent reporting standards • stable and accurate – fewer calibration checks are needed • covers a common flow range with accuracy (other sizes available) • combines with Neon to enable viewing of recorded data via the Internet • suitable for meeting the requirements of the current ‘>20 l/s’ legislation. NIWA’s Cascade T-120 flume system helps you meet your irrigation water consent obligations and improve productivity. Cascade T-120 enables the measurement of open-channel flow rates from 3 to 120 litres per second. Affordable and easy to install, the T-120 can be transported to a site on a light trailer. It can often be positioned and installed by one person.
Transcript
Max Oulton
National Centre for Environmental Information
NIWA’s Cascade flumemakes open-channel water flow measurementas easy as it gets
Weirs and flumes are useful for flow measurement, but…For open-channel water metering you need the right design to avoid:
• loss of flow from backwater, or flooding and overflowing upstream
• errors due to blockage by weed, debris and silt
• poor accuracy: not meeting the +/-10% requirement
• not measuring the full range of flows.
The benefits of NIWA’s Cascade flumeA Cascade flume, when properly installed, will solve these problems for its recommended flow range.
Practical benefits• needs little maintenance – passes debris and sediment
• suitable for sites with little fall (unlike a weir)
• greatly simplifies flow-rate measurement
• inexpensive – from purchase, through installation to ‘old age’
• easy to handle – plastic-moulded in one piece, lightweight (68kg)
• easy to install – dig in, level, retain with concrete (0.55m3), mix on site.
Compliance benefits• complies with current flow consent reporting standards
• stable and accurate – fewer calibration checks are needed
• covers a common flow range with accuracy (other sizes available)
• combines with Neon to enable viewing of recorded data via the Internet
• suitable for meeting the requirements of the current ‘>20 l/s’ legislation.
NIWA’s Cascade T-120 flume system helps you meet your irrigation water consent obligations and improve productivity.
Cascade T-120 enables the measurement of open-channel flow rates from 3 to 120 litresper second.
Affordable and easy to install, the T-120 can be transported to a site on a light trailer. It can often be positioned and installed by one person.
enhancing the benefits of New Zealand’s natural resources
Measuring flow rateThe most convenient way to measure open-channel flow is to measure water level and convert it to flow.
Normally this requires many flow measurements (gaugings) to produce a ‘rating’ that provides a relationship between water level and flow rate. Then, if you know the water level, you can convert it to flow.
The flume has been designed with a known ‘rating’ that is the same for all correctly installed T-120 flumes. Unlike river sites where banks can be eroded by floods, requiring a new rating to be produced, the T-120 will always retain its design rating and requires infrequent calibration checks.
Installation is uncomplicated, as this video shows: http://www.youtube.com/watch?v=GHgwIwA_UxQ
As part of a Neon systemCombining a Cascade T-120 flume with a NIWA Neon data logging, processing and communications system gives you the flexibility of two options:
• flow measurement only
• flow measurement and control.
Adding a small control gate to your irrigation take isn’t complicated and it enables you to program and maintain a target flow rate. This option offers automation and remote control capabilities to manage and optimise your take while staying within the consent limits.
Because Neon is web-based, it enables you to view the flow records or change the flow target from anywhere you can access the Internet – on a desktop computer, tablet or Android Smartphone.
Almost every open-channel flow monitoring situation can be different, so please contact us for advice.
A newly installed irrigation flow monitoring station showing the Cascade T-120 flume. The solar-powered recording and telemetry equipment is up on the bank (out of sight). A modest amount of concrete fill retains the flume.
The flume is located as close to the ‘take’ as possible. Water enters the flume at top of picture and leaves at bottom. The water level in the flume is continuously measured and can be converted to flow rate by a data logger.
