Giant salmonflies (Pteronarcys californica) are an iconic species in rivers of the Rocky Mountains due to their large size and importance to a suite of aquatic and terrestrial predators, but their range is in decline. Salmonfly emergence, occurring en masse during 1-2 weeks in early summer, represents a substantial flux of carbon from rivers to adjacent riparian habitats. Despite their ecological and economic importance, little is known about the ways in which anthropogenic change, including changing flow regimes and drought, may influence salmonfly emergence density or phenology. Here, we evaluate long-term trends (2016-2022) in salmonfly emergence flux and timing in the Gallatin and Madison Rivers of Montana, USA. During November 2021, a dam malfunction on the Madison River caused large portions of the river downstream to dry for 48 hours. We predicted that this pulsed drying disturbance would cause salmonfly mortality and subsequently decrease emergence flux on the affected Madison River compared to the unregulated Gallatin River, and decrease emergence flux in 2022 compared to previous years. In contrast to our predictions, we found that emergence flux in both rivers was not different in 2022 compared to other years. Emergence timing, however, was delayed by 10 days on both rivers in 2022 compared to 2021. We speculate that this shift in phenology resulted, in part, from extreme high flows, and subsequent lowered temperatures, caused by a rain-on-snow event that occurred in mid-June 2022 rather than the pulsed drought event. Our data suggest that complex changes in river flows, such as extreme floods and droughts occurring simultaneously across watersheds, may drive unexpected patterns of emergence, posing consequences for terrestrial predators that rely on predictable emergence patterns. Forthcoming results will compare salmonfly carbon flux with that of other aquatic invertebrates to assess the relative importance of salmonflies to total annual carbon export.