Water Level Monitoring

Water level can be measured using any one of the methods below: The measurement methods include:

• Method 1 – a still well or still pipe with a shaft encoder with a float and beaded float line system.
• Method 2 – a pressure sensor which is immersed into the stream or river.
• Method 3 – the more complex pressure bubbler system which allows for a small open tube to be immersed into the stream or river with a gas pump or gas cylinder to inject small bubbles into the open tube and measure water depth by measuring the back pressure required to force bubbles out of the tube in the water.
• Method 4 – Measuring depth using Ultrasonics Doppler Instrument 6527.
• Method 5 – Measuring depth using Radar.

Application Detail

There are many measuring methods available, but still the most common method is a shaft encoder float and wheel system. This method requires a large well or a smaller pipe to be installed on the stream, river bank or on a bridge structure, to provide a stable, not disturbed by flow or wind, measurement environment.
A small float, a float line and a counter weight system will respond to depth/level changes in stream or river. That response causes rotation of the shaft of a wheel. Shaft rotation is measured very accurately by optical encoder and the data is simultaneously displayed and recorded in the data logger within the instrument.

The Unidata Model 6541 Precision Water Level instrument can achieve operating accuracy and resolution of 0.2mm. This accuracy is maintained for the service life of the instrument without calibration or maintenance, apart from battery changes. The 6541 instrument has the range to monitor surface and under- ground waters, and the precision to monitor rainfall and evaporation. The very low mechanical friction and inertia of the instrument means that it can produce data with high precision and accuracy. Unidata Precision Water Level Instruments have been installed at over 5000 sites. The power consumption of this instrument is tiny, only a few micro amps is needed to operate it, so it can be run on a single battery pack for more than a year.

The 6541 instrument is normally “connected” to the water surface by a float system. On installation, the instrument is set to display the water level. An optical encoder is mounted on the input shaft so, as the water level changes, the input shaft and encoder rotate. The rotation of the encoder is continuously monitored so the instrument tracks water level changes. These changes update the LCD display. Choice of encoding wheel diameter, length of float line and type of float will depend on the site conditions and measurement objectives.

A Water Level Instrument can be equipped with an internal micrologger that can store measured data or connected to a Neon Remote Logger to provide a temporary store of the data until it is transmitted to central Neon sever on a regular basis. When connected with a Neon Remote Logger you can monitor data recorded by the instrument and check the health of the site, all from a web browser on the internet.

This can be done over cellular or satellite communication links. Using telemetry decreases the need for time consuming site visits. When you use one of the telemetry options you may need to provide external power such as a solar panel, external battery and regulator.