Longhorn Dam makes no power; it passes what it is sent
Everything on this reach is decided upstream. Longhorn Dam, finished by the City of Austin in 1960, holds Lady Bird Lake behind nine floodgates and is not a hydroelectric dam; its release varies with rainfall and with the seasonal demand for irrigation water downstream. The water reaching it has already passed LCRA's chain, Buchanan (1938), Tom Miller (1940) and Mansfield (1942), and TPWD says flow below Longhorn is regulated specifically by Buchanan and Mansfield. LCRA sells stored water to rice irrigators in Matagorda, Wharton and Colorado counties and decides on March 1 and July 1 how much interruptible water goes to first and second crops.
USGS 08158000 at Austin sits at the US 183 bridge, the first public access below the dam, and measures that release plus little else. Walnut, Onion and Decker creeks all come in below it, so rain on the east side of town can muddy Bastrop without moving the Austin number. In the second half of September 2026 the gauge swung almost daily between about 200 cfs and 1,500 to 1,650, topping 2,310 on September 16, while Bastrop held between 890 and 1,190. Nobody publishes a wading figure; All Water Guides fishes this river from jet skiffs. The 200 to 1,200 cfs range on this page comes from USGS instead: the floor is the between-release low of September 2026, the top is the long-term mid-September median at Austin. TPWD's lease pages add that turbidity is highest when Highland Lakes releases are being made, and bass fish best when it is low.
US 183 to Fisherman's Park, by LCRA's mileage
LCRA's river guide counts access in miles from Longhorn Dam: US 183 at the start, the FM 973 bridge at Del Valle at 9 (limited parking, a rough carry), Little Webberville Park at 21, Big Webberville Park at 26, the FM 969 bridge at Utley at 40, Bob Bryant Park in Bastrop at 53 and Bastrop Fisherman's Park at 54. Between US 183 and FM 973 a low-head dam 4.75 miles down has to be portaged on river left. LCRA's rule is that paddlers average two to three miles an hour, so divide the miles by two for rough hours.
Two TPWD leases fill gaps. Texas River School's camp in east Austin, on the north bank about 3.5 miles below the Montopolis bridge, has 225 feet of bank and eight primitive sites, reserved by email a day ahead. Horseshoe on the Colorado near Bastrop is the take-out for a 7.4-mile float from Big Webberville Park or the put-in for 6.8 miles to the Utley ramp; text (512) 970-9739 a day ahead and sign a waiver. Below Utley, TPWD's Bastrop Wilbarger paddling trail runs about 14.3 miles to Fisherman's Park, and the El Camino Real trail about 6 more to Lost Pines.
The slot ends at the dam
Lady Bird Lake above Longhorn Dam has a 14 to 21 inch largemouth slot, and so does Lake Bastrop, but the river between them does not. TPWD's exceptions list doesn't name the Colorado, so statewide limits apply: five black bass a day in any combination, 14 inches for largemouth and smallmouth, no minimum on Guadalupe bass, 25 white bass at 10 inches, and one alligator gar a day, reported within 24 hours. TPWD's lease pages ask anglers to practice catch-and-release here, especially for largemouth and Guadalupe bass. Anyone who takes you fishing for pay needs a Texas fishing guide license.
TPWD classifies this reach as navigable: the bed is public, and the banks may be used only to portage a hazard. The banks are generally private, so rest on an island or a gravel bar, and read purple paint on a post or tree as a no-trespassing notice.
A 3.71-pound fish, and the smallmouth question
On February 1, 2014, Dr. Bryan Townsend, fly fishing with guide Shea McClanahan, landed a 3.71-pound, 17-inch Guadalupe bass from the Colorado below Austin, and later TPWD pages call it the state record. TPWD's biologist described the river from Longhorn Dam to La Grange as a special bass fishery where two- to three-pound Guadalupes are reported frequently and 50- to 100-fish trips are not uncommon. All Water Guides adds largemouth over five pounds with a handful over seven, drum to 15 pounds on a fly, and spotted, longnose, shortnose and some alligator gar. The blue sucker, state-threatened, is one of the most common fish between Webberville and Smithville.
Smallmouth get mentioned with Austin, so here is what the record shows. TPWD stocked smallmouth in Onion Creek, a tributary of this reach, from 1974 to 1980, and stopped when they were found hybridizing with Guadalupe bass. We found no source describing an established smallmouth fishery below Longhorn Dam, so treat one as a bonus fish. The white bass run belongs above the Highland Lakes: on Lake Buchanan the fish go up the Colorado from February to May, and at Colorado Bend State Park you can wade for them without a license.
Crawfish in February, poppers near seventy
All Water Guides' reports make a usable calendar. In winter the bass sit deep and eat anything dark and crawfishy, and some of the year's biggest fish come then, except right after a strong cold front; a February 2013 trip found the water in the mid 60s and gin-clear and caught fish on streamers and crawfish patterns on a sinking line. March and April are, in their words, two of the best months: Clouser Minnows and weighted leeches early, then poppers and big deer-hair divers once the water nears 70 degrees.
Summer slows the bass, so start at first light and look for gar on the flats; Alvin Dedeaux's own Snake fly in white, pink or chartreuse and his popper carry the heat. The bite comes back from mid-September into early October, when poppers, minnows and deep-sunk crawfish patterns all work again.