A spring, not a dam
Mammoth Spring comes up in the state park at the Missouri line, and the Encyclopedia of Arkansas gives it an average of 9.78 million gallons an hour at a constant 58 degrees, the largest spring in the state. AGFC puts the same flow into a 10-acre lake behind Dam 1, and below that the Spring River is trout water for about 12 miles, down to the mouth of Myatt Creek near Hardy. There is no generation schedule to read. The water that reaches you is spring water, and it changes slowly: the USGS gauge on the spring itself averages about 277 cfs in October and 436 in May across its record.
The dams are old industry. A milldam went in at the spring in 1887, the Arkansas-Missouri Power Company ran a hydro plant there from 1925 until 1972, and Dam 3, a few miles down, is another retired power structure with a slow lake stretching about a mile above it.
Wading the top three miles
From Mammoth Spring to Dam 3 is the wading water. The AGFC map has Lasseter Access, with no ramp, off Riverview Road; Cold Springs Access half a mile off Highway 63, with a paved ramp and a pier built for mobility-impaired anglers; and Dam 3 Access, 3.2 river miles below the spring, with a ramp, a fishing jetty and a foot trail to the main channel. The water right above Dam 3 is deep; the rest of this stretch can be walked or fished from the bank. It is how most people fish the river: 96 percent of anglers in AGFC's 2024-25 creel survey were on the bank or wading.
The bottom is solid limestone and slick, which Mark Crawford of Spring River Flies and Guides mentions whenever the flow rises. He normally fishes 3X because of the river's green tint and drops to 5X when it runs low and clear.
Below Dam 3, where the kayaks are
Bayou Access, off Highway 289, is 5.9 river miles from the spring, and the unnamed Many Islands Road site on AGFC's map is at mile 11; Hardy Beach Access in town has a ramp and dock. Both banks below Dam 3 are mostly private, which is why AGFC's management plan talks about negotiating boat access with the resorts. Float NWA warns that Saddler Falls and the falls at Many Islands flip canoes and tubes and should be scouted or portaged. AGFC does not allow overnight camping at its accesses.
This is also where the rental boats go. Crawford says the canoe traffic starts at the end of May and is worst on Saturdays; by early September it is fading. The creel survey found 79 percent of recreational floating on weekends and holidays, and advised that between Dam 3 and Bayou you meet fewer floaters before 10 a.m. or after 2 p.m.
A trout permit, five fish and the new brown minimum
From 100 yards below Dam 1 at Mammoth Spring State Park to the mouth of Myatt Creek, a trout permit is required to fish, you may use one rod and must attend it, and a bait hook may carry only one point. The daily limit is five trout with only one over 14 inches. From July 1, 2026 the minimum length for a brown on the Spring is 16 inches, a change the creel report recommended after finding it would raise the number of 16-inch browns by about a fifth. The two-trout emergency limits on the White, Norfork, Little Red and Beaver tailwaters do not apply here, and there is no catch-and-release or artificial-only section.
Two more rules matter for bass anglers. The whole Spring is now a Blue Ribbon smallmouth stream, one fish over 15 inches, and the guidebook closes the Spring and its tributaries to crayfish fishing.
The flood of April 2025 and the fish it left
On April 5, 2025 the river at Imboden peaked at 128,000 cfs, second only to the December 1982 flood, and Crawford described a surge of more than 15 feet. It emptied the federal hatchery at Mammoth Spring and the state's Jim Hinkle hatchery into the river; AGFC's creel report counts about 589,000 rainbows stocked that year, most of them by accident, and its biologists expected escaped tiger trout to turn up for a few years. The state hatchery ran at half capacity afterward, and Crawford reported no stocking below Dam 3 until winter 2026. The management plan's normal target is about 104,000 rainbows of 11 to 12 inches and 10,000 nine-inch browns a year.
What the Hardy gauge shows on a normal day
USGS 07069305 at the Spring Street bridge in Hardy sits at the bottom of the trout water, so it reads the spring plus everything that has come in along the way. Between September 10 and 24, 2026 it ran 248 to 369 cfs, mostly 291 to 314, while the spring gauge upstream held at 229 to 250. Crawford's reports are keyed to the spring, where he calls 350 cfs average, 290 easy wading and 380 a rise with poor clarity. The 250 to 500 cfs band on this page is those spring numbers carried down to Hardy, where September readings run about 40 cfs higher; it is an interpretation, not a shop chart. Hardy's long-term monthly means climb from about 550 cfs in September to 2,081 in April, and that difference is rain, not the spring.
Caddis and olives, and a bead-head olive Woolly
No one has published a hatch chart for the Spring, and AGFC's own creel report proposes drift-netting to learn the timing. Crawford's reports fill in the year: caddis and blue-winged olives with trout rising in February, midges and caddis emergers in early spring, mayflies and caddis most days in May, damsels and hoppers in summer with caddis egg-layers late in the evening. He calls a bead-head olive Woolly the streamer and fishes sculpins for smallmouth near Hardy. Perfect Fly adds scuds and sowbugs to the menu.