A low-cost sensor array was developed to measure the vertical temperature profiles in stormwater detention ponds. The array consists of a series of iButton® temperature sensors (manufactured by Dallas Semiconductor) that are attached to a fishing rod, which is weighted at one end. An iButton® sensor comprises a thermistor, data logger and power supply, all of which are housed in a case that is about the size of a large watch battery.
As each iButton® sensor contains its own datalogger and power supply, it eliminates the need to run cable to an onshore system or to sink the datalogger and power supply in a waterproof case, reducing the cost significantly. Also with no wires in the array, the sensors can be easily arranged and rearranged to record temperatures at any configuration of depths.
In the fall of 2009, a two-metre array, with sensors every ten centimetres, was placed into a stormwater detention pond in Regina, Saskatchewan. The array recorded temperatures at half-hour intervals for 36 days. The temperature measurements show two intermittent boundary layers exist at the surface and the bottom of the pond and that there can be several degrees difference between these layers and the middle layer of the pond.