Executive Summary:

Stationary ice formation, a natural occurrence in northern hemisphere streams during winter, has significant impacts on the hydrology and ecology of a stream. From December 2020 through March 2021, Roaring Fork Conservancy researchers conducted a pilot study on the Lower Fryingpan River to better understand the parameters affecting anchor ice formation in the river. Anchor ice presence was observed 13 out of the 32 survey days. A decrease in anchor ice presence started in the second half of January 2021 and continued through the end of the study period. This decrease in anchor ice aligned with observed increases in water temperature, air temperature, and stream flow rate. Logistic regression modeling substantiated these observations with statistically significant results showing a negative correlation between those three independent variables and anchor ice presence. While the results from this initial period of anchor ice monitoring provides a strong basis for future studies, improvements can be made to protocol and methodology to strengthen the integrity of the data moving forward. Additionally, continuing the study for at least five more years will provide more evidence necessary to make definitive conclusions about the influence of water temperature, air temperature, and stream flow rate on anchor ice formation in the Lower Fryingpan River.