TROD: Temperature Profiling Probe

Discrete subsurface temperature measurements have been made in stream environments using three basic approaches:

1. Individual self-logging temperature sensors inside an in-stream pipe (a, piezometer)
2. Thermocouple or thermistor type arrays that measure temperature at multiple points and are wired into a single electronic data-logging device (b, thermocouple array)
3. Fiber-optic type distributed temperature sensor (FO-DTS) that measure temperature at many locations with depth (c, FO-DTS)

Each of these approaches have pros and cons; the suitability of each of these approaches is dependent on the environmental application and specific needs of the study. Deployment of temperature sensors using these methods may be limited to shallower surface water depths and can be susceptible to damage at high stage from increased velocity or debris.

The TROD is an improvement in the design of approach 1 and consists of multiple self-logging temperature sensors in a 1 m probe. The TROD has several advantages over traditional methods:

• Low-profile design allows for continuous monitoring in harsh environments that are susceptible high-discharge events when damage from sheer or rapidly moving sediment or debris is likely.
• Does not require removal or disruption for data retrieval. In a typical piezometer installation, data are obtained by removing temperature sensors from the piezometer and downloading data individually. Data are retrieved from the TROD through the submersible communication cable or by direct contact with the head of the probe using reader for all sensors simultaneously.
• Uses low-cost existing self-logging temperature sensors that are easily replaced and allows prolonged use of the components.
• User friendly software has been developed that is efficient in programming and retrieval of temperature data.

A version of the TROD has been constructed for use without the communication cable for situations where visibility may expose the instrumentation to vandalism (i.e., urban streams) or where burying the cable may be impractical (i.e., dynamic lake shore environments). The sensor spacing interval and depth can be chosen to optimize observation density for a variety of applications.

Methods for monitoring sediment temperature in a surface water system. The dash line indicates high stage conditions with water submerging the top of the piezometer.

TROD with and with out the communication cable.