Sixty-two degrees at mile 1.3
Canyon Dam draws from the deepest point of Canyon Lake, which cools to about 54 degrees in winter, and that is the only reason a trout survives in Comal County. GRTU's temperature study found that released water warms to the river's natural temperature in about 36 hours, and that a 200 cfs release stretches trout water from about 4 miles below the dam to at least 10, down to the 3rd Crossing. GRTU keeps loggers at miles 1.3, 2.9, 6.7, 7.5, 8.6 and 9.6. On September 24, 2026 the top one read 62.8 degrees and the bottom one 69.0.
GRTU's rule for those numbers is short: fish with care at 65 or below, use caution from 65 to 68, and stop trout fishing above 68. The study's station miles turn that into a map. Highway 306 is mile 4.0, Ponderosa 7.4, the 3rd Crossing 10.5 and the 2nd Crossing 13.8, where summer spikes can reach 76 degrees. In the 2000 drought, the study says, only trout living within the first 2 miles below the dam would have survived.
Zone 1, Zone 2 and the 800-yard signs
From the base of Canyon Dam to the large signs posted 800 yards downstream, the statewide trout rule applies: five a day, no restriction on method. Trout Zone 1 runs from those signs to the east bridge on FM 306. There TPWD uses a 12 to 18 inch slot: you may keep trout 12 inches or less or 18 or more, five a day, only one of them 18 or longer, and harvest is by artificial lures only. That slot took effect September 1, 2014. Zone 2 runs from the east FM 306 bridge down to the 2nd Crossing on River Road: one trout a day, 18 inches minimum, artificial lures only. Below the 2nd Crossing the limit reverts to five fish.
Artificial means what TPWD says and GRTU reprints: no fish, crayfish, insects, worms or other animal or vegetable material, and no scented synthetics, though hair and feathers are fine, and it is an offense to possess trout in the special reach while fishing any other way. You need a license with the freshwater endorsement unless you are under 17. Guadalupe bass have no minimum length and count in the five-fish black bass bag, where largemouth must be 14 inches. GRTU asks everyone for single barbless hooks and makes its lease members release every trout below the dam; neither is state law. Some shop summaries of these zones are wrong, so read TPWD's waterbody page.
Paying for a place to stand
The streambed below Canyon Lake is public and the banks are private, all of them. Texas law lets you wade and fish a navigable bed but gives no right to cross private land to reach it, and fishing from the deck of a TxDOT bridge is an offense. That leaves three ways in. Guadalupe Park, run by the Corps of Engineers, is open all year. TPWD leases winter access; its last posted lease, Camp Huaco Springs on River Road about 0.3 miles south of the first bridge crossing, gave roughly half a mile of bank from December 6, 2024 to March 2, 2025. The Texas Rivers Protection Association lists commercial access at the FM 306 bridges, Rio Raft at the 4th Crossing and Lazy L&L, and Rio Anglers, just above the 4th Crossing bridge, has a quarter mile of walk-and-wade frontage.
The third way is GRTU's Lease Access Program, which pays landowners for parking and wading at 14 private locations. You must be a GRTU member, attend a Zoom orientation in September, then buy the permit in October: $200, capped at 800 memberships, with up to six $20 guest passes a year and a $20 youth pass for anglers 17 and under who fish with an adult member. That group, TRPA, describes the season as November to April, before tubing season, which it calls the rubber hatch.
Sattler, the 90 cfs floor and the 150 cfs deal
USGS 08167800 at Sattler sits a few miles below the dam and reads Canyon's release with little added. From September 10 to 24, 2026 it barely moved, 140 to 166 cfs. The Corps owns and operates the dam, GBRA owns the stored water and the hydro plant, and the federal hydropower license requires a continuous 90 cfs, scheduled at 100 to 120 cfs by month outside drought. What holds summer water up for trout is GRTU's contract with GBRA, dated January 26, 2016: a 150 cfs daily minimum from May 16 through September, provided the lake reaches 909.0 feet and stays above 905.0. It ends December 31, 2026, and GRTU says renewal talks are friendly.
GRTU's safety chart for this water calls 100 to 250 cfs average, good for floating above 150, and that band is the range on this page. From 250 to 350 every wader should carry a staff, 350 to 550 is high, and above 650 GRTU recommends raft trips only. The USGS daily median at Sattler for mid-September is 135 cfs, so the current water is ordinary. When Canyon Lake is above 909 feet the Corps controls outflow, and the Comal County water district calls anything over 3,000 cfs dangerous.
December trucks, June tubes, and the bass underneath
TPWD stocked 18,471 rainbows in the Canyon tailrace on ten dates from December 5, 2025 to February 26, 2026, at Guadalupe Park, Whitewater Camp, the 4th Crossing, the 3rd Crossing and Camp Huaco Springs. GRTU adds about 16,000 pounds of rainbows a season and plans four stockings for 2026-27, and it reports a bigger holdover class this fall, mostly 13 to 16 inches and fat from supplemental feeding. Orvis's report puts the average trout at 12 to 14 inches, with fish over 20 not uncommon. Rio Anglers fishes midges, zebra midges and olives in 18 to 22 through winter, caddis and hare's ears from March, ants in April and hoppers and beetles by May.
After Memorial Day the tubes arrive. Orvis says summer traffic plus warm water makes trout fishing very difficult, and in unincorporated Comal County the water district bans foam and glass and requires life jackets on children 12 and under. That is when the river becomes bass water. Guadalupe bass, the state fish since 1989, spawn from March into June and hold in the quicker riffles, and TRPA suggests switching to stripers or largemouth after March, noting trout-eating stripers of 20 to 30 pounds below Canyon Dam. In fall, Rio Anglers turns to streamers, woolly buggers and crawfish patterns until the first stocking truck.