417 feet of concrete and no ladder
Owyhee Dam went up between 1928 and its dedication on July 17, 1932, 417 feet tall, and it was built without a fish ladder, which ended the Chinook runs that had come up from the Snake. What it made instead is a cold tailwater in sagebrush country, with hatchery rainbows and brown trout in the water below the dam. The dam's purpose is irrigation, and that shapes everything about the fishing.
ODFW's July 28, 2026 report described the lower river as brown trout and hatchery rainbows, with the release from the dam at about 116 cfs, and asked anglers to report any tagged fish because the agency is running a tagging study in the tailwater this year.
Brown trout go back
The Owyhee sits in ODFW's Southeast Zone, where streams are open all year with a default of 2 trout a day, 8 inches minimum. The Owyhee has its own exception in the 2026 regulations: 5 rainbow trout a day, 8 inches minimum, and brown trout catch-and-release only. Bait is allowed. Nothing in ODFW's in-season updates as of September 24, 2026 changes that.
Two cautions go with the rule. The state's fish advisory lists the Owyhee upstream to Three Forks for mercury in all resident fish, one more reason to release them. And in fall, when the browns spawn, Idaho Angler in Boise has asked people to stay off the river; its October 18, 2025 report came with flows near 30 cfs and browns on their spawning beds. Low water and spawning fish make fall the time to leave them alone.
Irrigation water, then almost none
USGS 13183000 sits just below the dam and reads the release directly. The pattern since 2010 is stark: monthly means of about 1,030 cfs in April and 580 in May during spring releases, 360 in June, then about 199 in July, 189 in August and 169 in September while irrigation water goes downstream. After the season ends it falls to about 78 in October and 26 to 28 from November through January. Idaho Angler called flows around 150 optimal in its April 21, 2026 report, and the summer means sit right at that level, so the 100 to 200 cfs on this page is the irrigation-season band. A reading under 100 means the irrigation season is over or ending.
Bureau of Reclamation's Hydromet station for the dam, which ODFW links, shows reservoir content alongside the release. In late July 2026 the reservoir was about 34 percent full and the Leslie Gulch ramp was out of the water.
Size 20 and smaller
This is a small-fly river. Idaho Angler's spring box for the Owyhee reads like a tailwater list anywhere in the West, but the sizes matter: Split Case BWO in 18 to 22, Juju Baetis 18 to 20, Glass Bead Zebra Midge 20 to 22, Hackle Stacker BWO 20 to 22 for rising fish. In April 2026 it said the olive hatches were weather dependent, stronger on cloudy days, and that PMDs and caddis had come early, fished with Split Case PMD and Extended Body PMD in 16 to 18 and DOB Caddis in 14 and 16. A San Juan Worm stays on the list all year. By fall the list shrinks to midges in 20 and 22 and a size 18 parachute ant.
Most Idaho anglers come in through Nyssa, and Idaho Angler points them to The Rock Store there for an Oregon license on the way out, since an Idaho license is no good on this side of the line. Its April list also carried Flashback Pheasant Tails in 16 to 20, a Jig Angel Case PMD in 18 to 20 and a CDC Thorax BWO in 18, and it said nymphing and dry flies were both producing, which is the usual split on a river this clear: nymph the riffles in the morning, look for heads in the flats when the clouds come over.
Rome to Leslie Gulch
Above the reservoir the Owyhee is a different river entirely. Congress designated 120 miles of it, all classed wild, as Wild and Scenic in 1984: the main stem from Three Forks to China Gulch and from Crooked Creek down to the reservoir, and the South Fork from the Idaho line to Three Forks. Little Creek Outfitters floats 55 miles from Rome to Birch Creek or Leslie Gulch over five days, and says the season is late March through May at best, depending entirely on snowpack. A 2019 bill to add wilderness and another 14.7 Wild and Scenic miles stalled and is not law. Check snowpack before planning it.