Colorado has more high-quality tailwaters packed into one state than anywhere else in the West, and it has a formal name for its best water: Gold Medal, a designation Colorado Parks and Wildlife gives to rivers and lakes that meet its standards for large trout. The Frying Pan, Blue, Taylor, South Platte and Gunnison all carry it and all run below dams. Alongside them are big freestone rivers, the Arkansas, Roaring Fork, Eagle, Colorado and Cache la Poudre, which blow out with snowmelt in May and June and then fish through fall. Knowing which kind of river you are standing on is most of the battle in Colorado.
The Frying Pan and the Roaring Fork Valley
The Frying Pan River below Ruedi Reservoir is a small, clear tailwater with a famous reason for its oversized rainbows: Mysis shrimp flushed out of the reservoir. Midges run through the winter, Blue-Winged Olives peak in spring and fall, Pale Morning Duns arrive in June and July, and the Red Quill hatch in spring and again in early fall is specific to this river. Ideal flows are only 50 to 400 cfs, and the fishing is #20 to #24 midges and #18 to #22 RS2s on 6X. It joins the Roaring Fork at Basalt, and the Fork from Aspen to Glenwood Springs is the valley's freestone: Salmonflies in late May and June, Golden Stones and caddis through July, hoppers from August. The Eagle River, one valley north through Vail country, is a similar freestone with a similar calendar. The Crystal River is a gauged tributary without a page.
The South Platte: Cheesman Canyon and Deckers
The South Platte River below Cheesman Reservoir is the Front Range's technical tailwater, an hour from Denver and fished hard. Cheesman Canyon is hike-in water with wary browns and rainbows; Deckers, downstream, has road access along River Road. Midges dominate, and the fly list reflects it: Zebra Midges to #26, Jujubee Midges, Mercury Blood Midges and Poison Tungs in #22 to #24, with RS2s for the Blue-Winged Olives that peak from fall through April and Tricos in August. Upstream, Spinney Mountain Reservoir is Colorado's only Gold Medal stillwater and Eleven Mile Reservoir next to it holds trout, pike and kokanee. Both fish best from a float tube right after ice-out in late April and May.
The Arkansas from Salida through Brown's Canyon
The Arkansas River is Colorado's most accessible Gold Medal freestone, with public water for miles along US-50 and US-285 from Salida down through Brown's Canyon National Monument to Coaldale and beyond. The caddis hatch that starts in April and runs through summer is the famous one, timed ahead of runoff, and Salmonflies follow in late May and June. Once the river drops in July it is a classic dry-dropper river with Chubby Chernobyls and Stimulators in #6 to #8 on top and a Pheasant Tail below. Ideal flows are 200 to 2,000 cfs; the river is heavily rafted through Brown's Canyon in summer, so fish early.
Gunnison country: the Gunnison, the Taylor and Blue Mesa
The Gunnison River below Blue Mesa flows through the Black Canyon, where designated routes drop steeply to the water and reward the descent with large browns, then through the Gunnison Gorge below. Above the reservoir, the Almont confluence is where the East River joins the Taylor River, a Gold Medal tailwater below Taylor Park Reservoir known for its short, heavily fished trophy section right below the dam and miles of more forgiving water downstream. Blue Mesa Reservoir is the state's largest lake and one of the West's better kokanee fisheries. The Lake Fork of the Gunnison, gauged with temperature, is a serious trout river that lacks a page here.
The Blue, the Colorado and Grand County
The Blue River below Dillon Reservoir runs through Silverthorne as a small Gold Medal tailwater with Mysis-fed rainbows and midge and Blue-Winged Olive fishing much like the Frying Pan, at flows of 50 to 400 cfs. It joins the Colorado River in Grand County, and the Colorado from Pumphouse to State Bridge is a float-and-wade river with caddis from April, Pale Morning Duns in June and July, and hoppers in August. Gore Canyon above Pumphouse is hike-in water. The Fraser and Williams Fork, both gauged with temperature, feed this reach and are unwritten here.
The Poudre, the Front Range canyons and the unwritten Western Slope
The Cache la Poudre
The Cache la Poudre River is Colorado's only designated Wild and Scenic River, running out of Rocky Mountain National Park down Poudre Canyon to Fort Collins. It is a pure freestone with rainbows, browns and cutthroat, a Salmonfly hatch in June that usually meets runoff, and its best fishing from July into October with Stimulators and hoppers. The Big Thompson, Clear Creek and Boulder Creek are the neighboring Front Range canyon streams, all gauged and awaiting pages.
The Western Slope and San Juan country
Colorado's southwest and northwest are rich in trout rivers this site has not written up yet, all of them USGS-gauged: the Yampa through Steamboat, the White River and its forks near Meeker, the Animas through Durango, the Dolores, the San Miguel, the Uncompahgre, the Rio Grande near Creede and the Piedra and Los Pinos in the San Juans. Most are freestone and follow the July-to-October calendar.
Before you go
Gold Medal water often comes with special gear and bag rules, and they differ river to river; confirm current regulations with Colorado Parks and Wildlife. Tailwater flows can change overnight with reservoir operations, so check the gauge the morning you go. For every gauged water in the state see the Colorado fishing hub, and for trout detail the Colorado trout page.