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Dilution Gauge Apparatus

The flow rate of a fresh water stream has traditionally been measured by manually dispensing a saline solution into a stream and then measuring the water's conductivity further down-stream using a conductivity sensor.
The manual method of dispensing a saline solution into a stream is simple enough and generally works well but it is very time consuming and cannot be carried out for the entire day. More importantly, there is a considerable change in the flow rate of Antarctic streams over the course of a day, depending on temperature, solar radiation and the quantities of snow around the area.

Early in the day air temperatures are low and the heat of the sun is fairly weak, so the flow rates are slow. As the day passes by the air temperature may rise and the sun become stronger and so the ice and snow starts to melt, hence, the flow rate of the stream increases.

To understand these fluctuations over a long period would take a lot of time and restrict the operator to one stream at a time. Melts often occur suddenly so it is vital not to miss this or inaccurate data will be recorded.

The Dilution Gauge Assembly automates the method for measuring the flow or volume of water moving down a stream in a set time. The technique involves adding a known amount of a saline solution (NaCl) into a stream and monitoring the passage of the "slug" of saline solution (high conductivity) past a sensor situated further downstream. Readings are taken at regular intervals from the moment the salt is added until the conductivity of the stream returns to normal. All the data is recorded on to a computer.

A reservoir containing a pre-mixed saline solution is mounted above the apparatus and feeds via gravity into a dispensing valve mechanism.