<p>Bull trout (<i>Salvelinus confluentus</i>) are a species of char listed as threatened in the United States under the Endangered Species Act. Two critically depressed populations persist in Kachess Reservoir of the upper Yakima River Basin in Washington State. Due to proposed changes in water management and the lack of information on the movement ecology of bull trout in Kachess Reservoir, we initiated this study to better understand these populations. We used acoustic telemetry to describe spatiotemporal movements of bull trout, identify barriers to movement across a constricted passage corridor in the reservoir called The Narrows, and define correlates of depth distribution. Our study spanned both non-drought (2022) and drought (2023) years as defined by the state of Washington, between which the water surface elevation in Kachess Reservoir varied substantially. Bull trout distribution shifted south in 2023, with most fish moving south of The Narrows by mid-summer. While movements across The Narrows in both directions occurred throughout 2022, no bull trout crossed The Narrows after July 2023, suggesting that lower water levels resulted in barriers to movement. Bull trout depth distribution showed significant, consistent diel vertical migrations, while average depths were similar across years. With more lentic habitat located south of The Narrows, but both spawning tributaries only accessible north of The Narrows, it is essential to maintain passage for bull trout across this corridor to ensure access to spawning tributaries.</p>