Three dams, and where the fish stop
The North Santiam runs 92 miles from Santiam Lake in the Mount Jefferson Wilderness to its meeting with the South Santiam, and dams cut it in two. Detroit Dam holds back Detroit Lake, Big Cliff Dam sits just below it near Mill City, and Minto Dam sits a short way downstream. Big Cliff blocks the migrating fish, so the lower river from Mill City down past Mehama, Stayton and Jefferson carries the spring Chinook and summer steelhead, and everything above the dams is managed as stocked trout water.
Several stretches near the dams are closed and are easy to fish by mistake. ODFW's markers at Packsaddle Park up to Minto Dam are closed to all angling, the first 400 feet below Big Cliff Dam are closed, the water from ODFW's markers between the footbridge and the 1st Avenue Bridge in Mill City up to the falls is closed, and so is the Stayton power canal.
ODFW's number is 3,000 at Mehama
This is one of the few rivers where the agency itself gives a flow. ODFW's Willamette Zone report says river levels best for fishing are at or below 3,000 cfs at the Mehama gauge, USGS 14183000, which sits 38.7 miles above the mouth between Mill City and Stayton. The low end on this page, 1,100 cfs, is the August mean since 2010 (about 1,170); July averages about 1,400, September 1,790 and October 3,180, after which winter means climb past 5,000.
On September 24, 2026 Mehama read 1,610 cfs. Summer flow here is largely what the Corps of Engineers releases from Detroit and Big Cliff, and in June 2026 the Corps announced a deep drawdown of Detroit Reservoir to help juvenile salmon get past the dam, so watch the gauge rather than the weather forecast when releases change.
What is in the river, month by month
Every fish here climbed Willamette Falls first, and the counts there set the calendar. Columbia Basin DART recorded 33,099 Chinook over the falls in 2025, most of them from April through June, and 9,971 steelhead, with the heaviest months from March through June. ODFW said in September 2026 that the summer steelhead run was better than average, with about 10,000 counted at the falls so far.
Late September is spawning time for the spring Chinook, and ODFW asks anglers to give spawning fish room and to keep dogs away from carcasses, which carry a toxin that is lethal to dogs. At the same time coho are arriving: ODFW expected the first fish in the Santiam basin in the last week of September with the peak in early October, along with a smaller late pulse of summer steelhead. Its advice is to swing large streamers or spin lures through the pools.
Mouth to Big Cliff: the 2026 rules
Under the 2026 regulations, from the mouth to Big Cliff Dam, the hatchery steelhead season is open all year; wild steelhead are open only July 1 through August 31; hatchery Chinook are open January 1 through August 31 and again from October 15 through December 31, so Chinook are closed right now; and hatchery trout are open May 22 through October 31, 5 a day with no minimum length. Coho rules change at the Stayton-Scio Bridge: below it coho are open all year, and from the bridge up to the Packsaddle Park markers coho are open January 1 through August 31 and from October 15 through December 31. Bait is allowed April 22 through October 31 on both reaches; from November 1 it is lures and flies only.
ODFW has extended the two-rod validation through December 31, 2026 on Willamette waters above the falls that are open to coho, which covers the lower North Santiam. It also reports the gate at Greens Bridge is open again until next June, and warns of several large downed trees in the lower river that are a hazard to boats.
Above Detroit Lake
Above Big Cliff the North Santiam and its tributaries are open all year, 5 trout a day at 8 inches, and bait is allowed. ODFW says conditions above Detroit are usually best from late June, once snowmelt drops, into early October; it ran about 300 cfs in late September 2026 and was last stocked in mid-August with about 2,000 hatchery trout spread across several release sites. A dead-drifted nymph or a slowly retrieved small spinner is ODFW's suggestion for the bigger fish. Near the headwaters, native cutthroat and rainbows share the water with introduced brook trout.