Thermal regimes in rivers and streams are fundamental determinants of biological processes and are often monitored for regulatory compliance. Here, we describe a simple technique for establishing annual monitoring sites that uses underwater epoxy to attach miniature sensors to large rocks and cement bridge supports, which then serve as protective anchors. More than 500 new monitoring sites were established using the technique from 2010 to 2012 in rivers and streams across the Rocky Mountains. Revisits to 179 sites indicate good sensor retention rates, with 88 - 100% of sensors retained after 1 year in low-gradient streams (3%). Establishing annual monitoring sites with underwater epoxy is inexpensive, can be done in a wide range of water temperatures, and improves data collection efficiency because few site visits are required and measurements are recorded throughout the year.