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Big Thompson River, Colorado
Report by Marc W. McCord

Drake to Gauging Station Take-out
~ 7.5 Miles

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SOAR Inflatable Canoes - Somewhere On A River

General Description

The South Platte River forms in the Pike National Forest of northern Park County, Colorado between Breckenridge and Alma near Hoosier Pass (elevation 11,541 feet msl), then flows southeast to Elevenmile Canyon Reservoir at Florissant Fossil Beds National Monument before turning to flow northeast through Cheesman Reservoir, into and through Denver to Greeley, where it then flows east by northeast to its confluence with the North Platte River at North Platte, Nebraska. It is a major Colorado waterway that is fed by numerous rivers and creeks including Clear Creek, Boulder Creek, Bear Creek, Big Thompson and Little Thompson Rivers, North and South Saint Vrain Creeks and others. The river is rated from Class I to V in various sections, and most tributary streams are rated Class IV to V+, or even VI.

The Big Thompson River, or Big Tommy, is an interesting Class IV to IV+ whitewater run that is wholly dependent upon water being released from Idyllwilde Lake just below Drake for navigable flows. Its short season is usually a May through June affair, as with several other Colorado streams. At flows below about 400 cfs runs are not recommended because Big Tommy is just too bony for fun paddling, requiring more walking than boating. It is optimum at flows right around 400 cfs, and "interesting" when flows exceed about 400 cfs. Putting in at Drake mandates portages around Idyllwilde Dam, the low-water bridge in Viestenz Smith Mountain Park and a diversion dam at Tunnel # 1 on SH 34 just above the take-out. Putting in just below Idyllwilde Dam eliminates the first portage and shortens the trip by about 1.3 miles. Campgrounds at either end of this run make it a convenient place to paddle just a few miles from Loveland and Fort Collins, when it has adequate water. Big Tommy can be paddled by canoes with flotation and kayaks, but strong intermediate or higher level whitewater skills are necessary. Rafts are not well-suited for this river.

One section, called "The Narrows" (I think EVERY river has one of those!), has the river flowing between a vertical canyon wall on river left and a concrete road/bridge abuttment on river right. The river is prone to flash flooding, so boaters should check local weather forecasts before going. There are few escape routes, and the potential for serious problems is great at high flows. Big Horn sheep may be seen grazing along the canyon side of this run. The very small Towns of Drake and Cedar Grove are located along this run, as is Viestenz Smith Mountain Park. The Cache la Poudre, Colorado and Fraser Rivers all have their headwaters in close proximity to the headwaters of Big Tommy, which flows through Rocky Mountain National Park, Roosevelt National Forest and Loveland to its confluence with the South Platte River near Greeley.


Larimer County in northcentral Colorado, just a few miles west of Loveland and a few miles southwest of Fort Collins.

Distance from major cities

Denver 75 miles; Fort Collins 36 miles; Grand Junction 300 miles; Durango 470 miles; Salt Lake City 585 miles; Albuquerque 512 miles; Phoenix 810 miles; Oklahoma City 700 miles; Dallas 860 miles; Austin 1,040 miles; San Antonio 1,023 miles; Houston 1,226 miles; Little Rock 1,016 miles; Kansas City 681 miles; (all distances are approximate and depend upon starting point, destination point on the river and route taken.)

Water Quality and Flow Rates

The Big Thompson River usually flows clean, clear and cold most of the time, but is not drinkable without purification. Dead-fallen tree debris may clog the channel at any time. Wearing a wetsuit or drysuit with a base layer will help prevent hypothermia.

Best time to go

The Big Thompson River is usually a summertime run from late-May through June, depending on dam-released water from Idyllwilde Lake. Be sure to check the gauges at Drake and below Lake Estes.

Hazards to navigation

There are no significant rapids that create hazards on Big Tommy. However, there are three mandatory portages between the Town of Drake and the guaging station take-out: Idyllwilde Dam on river left about 1.3 miles below Drake; Low-water bridge in Viestenz Smith Mountain Park on river left at about 2.3 miles below Drake; and Tunnel # 1 diversion dam just above The Narrows and below the Town of Cedar Grove at about 6.3 miles below Drake. There are no other significant hazards on this section of the Big Thompson River. Below the gauging station (and the overhead pipe) the river plunges into steep drops that may be a serious hazard to life and safety. Paddlers should not continue runs below the gauging station take-out.

River Access Points

Town of Drake, off SH 34 at 43 Road, on river left at 0.0 miles; Idyllwilde Dam, off SH 34, on river left at about 1.3 miles; Gauging station (overhead pipe) take-out on river right at about 7.5 miles. There are no other access points on this section of the Big Thompson River.

Campgrounds and accommodations

A campground is available along 43 Road near SH 34 at the Town of Drake; Three campgrounds are available just below the take-out on river right, along SH 34 between 29 Road and Loveland. Numerous other excellent campgrounds are available in state and national parks, and in national forests surrounding the Loveland-Fort Collins area. Motel and hotel accommodations are available in Fort Collins, Loveland and Boulder, all relatively nearby.

Liveries, outfitters and shuttle services

There are no known liveries or shuttle services operating on The Big Thompson River. Plan on providing your own boats, gear and shuttles.

Reviewer's comments

Big Tommy is a fickle stream that may or may not have adequate water to paddle. It also is characterized by a narrow window of navigability - too much below about 400 cfs makes it too bony to run, and too much above 400 cfs makes it dangerous because of the lack of eddies where boaters need to take out to portage the dams and the low-water bridge. Its May-through-June normal season dictates being in the general area during the times when water is being released from Idyllwilde Lake to catch a navigable flow. The area is quite scenic, though man-made construction does show its face along some reaches of this run. Its close proximity to Loveland and Fort Collins makes it convenient for obtaining food, shelter, gasoline and other requirements. Four campgrounds adjacent to the river, and numerous others in state and national parks and forests nearby, offer excellent opportunities for camping in the wilderness, but beware of grazing Big Horn Sheep, especially if you resemble the vegetation they normally eat. Avoid paddling downstream of the gauging station to prevent getting into very steep drops that may not be survivable.

Technical Data
Class Rating III to IV+
Length 7.5 miles
Minimum Flow 400 cfs
Optimum Flow 400-500 cfs
Maximum Flow 500 cfs
First Put-in SH 34 at 43 Road
Lat. / Long.
Last Take-out Gauging station (overhead pipe)
Lat. / Long.
Elevation 5,970-5,290 feet msl
Gradient 110 fpm
USGS Gauge Web: Loveland
Boats Canoes w/ flotation, Kayaks
Season May through June dam releases
Permits No

Poudre Paddlers Canoe and Kayak Club

Click HERE to visit the web site of Rocky Mountain Canoe Club

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Click HERE to visit the web site of Pikes Peak Whitewater Club

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Click the links below for information regarding the section of the South Platte River and its tributaries where you want to paddle.

South Platte River
[ South Platte River Homepage ] [ Fairplay to Hartzel ] [ Elevenmile Canyon Res. to Lake George ]
[ Lake George to Cheesman Reservoir ] [ Decker to Chatfield Res. S.R.A. ] [ North Fork Bailey Run ] [ North Fork Foxton Run ]

[ Clear Creek ] [ Upper Boulder Creek ] [ South Boulder Creek ]
[ Little Thompson River ] [ North Saint Vrain Creek ] [ South Saint Vrain Creek ]

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