We measure open channel flow for many reasons:

• Flow monitoring of irrigation schemes for compliance purposes
• To check for losses within an irrigation scheme
• Water Resource assessments for reliability
• In stream measurements to check minimum flow compliance

Flow Measurement
We measure flow in open channel irrigation races, rivers and streams. This is done using traditional flow measurement techniques to international and New Zealand standards, these have been specified by both NIWA and Regional Councils. Local standards can be found in Environment Canterbury’s NRRP.

Stage measurement
This is measuring the water level height using either a float and counterweight type water level sensor or a pressure type sensor. The water level is usually recorded every 15 minutes as a logger attached to the sensor. The height data is then converted into flow record using a stage/discharge curve. We also can measure groundwater levels using similar methods.

Stage discharge relationships
This is achieved by measuring flows at different water level heights, a curve is established as a mean of the measurements. The curve is then applied to stage record, to generate a flow record.