An Evaluation of Underwater Epoxies to Permanently Install Temperature Sensors in Mountain Streams

Abstract

Stream temperature regimes are of fundamental importance in understanding the patterns and processes in aquatic ecosystems, and inexpensive digital sensors provide accurate and repeated measurements of temperature. Most temperature measurements in mountain streams are made only during summer months because of logistical constraints associated with stream access and concerns that large annual floods will destroy sensor installations. We assessed six underwater epoxies to determine whether sensors could be attached to large rocks already in streams to provide durable installations and whether temperature measurements would be biased by heat conduction through the rocks. Only one of the six test epoxies bonded the sensors firmly to rock surfaces in laboratory trials. In subsequent field trials, 9 of 11 sensors attached to rocks with this epoxy successfully weathered above-average floods in four Idaho and Nevada streams in 2010. Comparisons of daily maximum, minimum, and mean temperatures between rock-mounted sensors and control sensors at 10 rocks suggested temperature measurements were not biased by attachment to rocks. We also assessed the effect of direct sunlight on sensors by removing solar shields from some sensors and noted rapid and statistically significant increases in daily means (+0.21°C) and maxima (+0.54°C), but not minima (−0.01°C). Use of underwater epoxy for permanent installation of temperature sensors in mountain streams is a viable technique if an appropriate epoxy is chosen, sensors are shielded from direct sunlight, and rocks large enough to withstand floods are used. Moreover, installations using epoxy are rapid (approximately 20 min), and firm attachments to rock surfaces over a range of stream temperatures (5–20°C) are possible.

Received September 16, 2010; accepted November 12, 2010

ACKNOWLEDGMENTS

This project was supported by the Rocky Mountain Research Station. An earlier draft of this manuscript was improved by comments from Brett Roper and Bruce Rieman. Mention of trade names does not imply endorsement by the U.S. Forest Service.