SonTek IQ Plus Velocity Index Discharge Compared to Historical Stage Discharge Curve

Abstract:

The SonTek IQ Plus bottom-mounted, up-looking Doppler Current meter is relatively new, low profile instrument specifically designed to measure water velocity in open channels through a wide range of conditions and water depth. The predecessor to the IQ, the SonTek Argonaut SW, is a well-established tool for measuring discharge in open channels utilizing a velocity index equation. The IQ builds upon this with velocity indexing capabilities and the addition of two skew beams and the implementation of SmartPulseHD.

The SonTek IQ Plus measures velocity with 4-acoustic transducers and the water level using a fifth vertically oriented transducer integrated with a pressure sensor. This improves upon previous and other bottom-mounted, up-looking, acoustic Doppler current meters by measuring the velocity at more points across the channel using its 4-monostatic acoustic transducers. Additionally, the vertically oriented transducer measures the water level and works in conjunction with the pressure sensor to provide a highly accurate water level/stage measurement. The implementation of SmartPulseHD enables the IQ to change ping type and processing technique based on water depth and velocity, in order to provide the most accurate velocity data possible.

The IQ was designed specifically for measuring open channel flow in irrigation canals and similar open channels, either by utilizing SonTek’s theoretical flow algorithm or using a velocity index equation. The study presented here demonstrates data collected by an IQ installed in an irrigation canal and the discharge computed using a developed index velocity equation. These data are then compared to discharge data determined by a conventional stage discharge curve developed over many years.

The data presented demonstrate the capability of the SonTek IQ to compute accurate discharge values based on an index velocity equation that was developed over a relatively short period of time.