Colorado’s Best Tailwaters

Tailwater fisheries offer year-round fishing opportunities and are especially important to fly fishers who pursue trout through the winter. While typical freestone rivers are jammed with ice, tailwaters remain fishable for several miles below the dam and reservoir, which provide a constant water source. The stretch of ice-free water below a dam depends on the depth of the reservoir, releases, water temperatures, and the gradient of the stream channel.

The greatest advantage to a tailwater fishery is this controlled source of water. Constant flows with ideal water temperatures, a weed-rich stream bottom with high levels of nutrients, and diverse aquatic insect populations are all key ingredients for growing large, healthy trout. Tailwater fisheries eliminate typical spring scouring by storing water and moderating flows. Later in the season a reservoir provides better-than-average flow when the natural flow would only be a trickle.

Tailwater fisheries share many common characteristics, yet each has its own distinct flavor. Some are great winter fisheries, some accommodate anglers looking for wild trout, and some are uncrowded. This list highlights some of my favorite Colorado tailwaters and what they have to offer.

Best New Tailwater

Arkansas River, below Pueblo Reservoir

When most fly fishers think of the Arkansas, they envision the river that flows unimpeded from the snow-capped Collegiate Range near Leadville, providing 150 miles of superb river fishing. Until recently, the upper Arkansas has overshadowed the tailwater below Pueblo Reservoir. But thanks to a multimillion-dollar stream improvement project that deepened the stream channel and added rock weirs and boulder gardens, the 8-mile stretch below Pueblo Reservoir has blossomed into a productive tailwater fishery.

This stretch fishes best between November and March when flows are stable. Summer flows vary erratically between 300 and 1,200 cubic feet per second (cfs) depending on irrigation needs. The river is tough to wade when flows exceed 600 cfs. Autumn flows average between 150 and 300 cfs, and winter flows after November 15 range between 70 and 140 cfs.

Anglers can expect hatches of midges, Blue-winged Olives, caddis, Yellow Sallies, Pale Morning Duns, and Tricos. Blue-winged Olives hatch all winter, and midge hatches make December and January two of the best months to fish dry flies. Consistent water temperatures from Pueblo Reservoir (mid 40s to low 50s) keep the trout active, and hatches are much more reliable, compared to other Colorado tailwaters at the same time of year.

The highest trout numbers are in the 2-mile stretch immediately below the dam. The Colorado Division of Wildlife (CDOW) stocks this section regularly with rainbow trout. Standard regulations apply but catch-and-release is strongly encouraged. The average fish in this section is between 10 and 13 inches long, with the occasional 15- to 18-inch holdover. There are also a few large brown trout but they are difficult to fool.

A bike path/hiking trail runs along the entire length of the river and there are seven parking areas for anglers, including a free lot just below the dam. To get there from Pueblo, take Highway 50 west, turn left (south) on Pueblo Blvd., turn right (west) on Pueblo Nature Center Road, and pull into the Nature Center parking lot. For more information, contact the Pueblo CDOW office at (719) 561-5300. The other parking areas between Valco Bridge and the dam require a Colorado State Parks pass, available at parks.state.co.us/.

The lower sections—between Tortillas Flats and Valco Bridge—offer the best fly-fishing experience. There are fewer fish and the fishing is technically difficult, but the rewards are worth the effort. Crowds are nonexistent and the average fish is between 13 and 15 inches, with some trout exceeding 17 inches. Every now and then, a large brown trout surprises you. The lower section is not stocked, but fish from above migrate downstream, taking on all the characteristics of wild trout.

Several techniques work well when pursuing these tailwater trout. A standard two-fly nymphing rig is especially effective in the riffles, runs, and pocketwater. Large #8-12 Prince Nymphs, crane fly imitations, and stoneflies, on a tandem rig with #16-18 tungsten Pheasant Tails, Mighty Mite Baetis, Mercury Pheasant Tails (natural and red), Sparkle Wing RS2s, and #18-20 Zebra Midges, Mercury Black Beauties, and Mercury Brassies are all effective.

Dry/dropper rigs are effective in the shallow riffles and mid-channel shelves. Use a #14-16 PMX, #12-16 Rubber-legged Stimulator, #16-18 Goddard or Elk-hair Caddis, or #14-16 Parachute Adams for a dry-fly indicator, and drop any small, flashy nymph below that. Trout rising in the flats can be spooky so use a long 12- to 15-foot leader. For most hatches I use an appropriately sized Parachute Adams and slightly smaller Mathews’s Sparkle Dun.

In autumn fishing streamers is often the best tactic to hook larger trout in the river’s lower regions. A #6-12 Barr’s Slump Buster (olive and rust), Black Conehead Bugger, or Halloween Bugger are good starting choices.