Horsetooth Reservoir stands as one of Fort Collins’ treasured trinity that includes the Poudre River and Horsetooth Rock.
A million visitors flock annually to its water cradled in the arms of four dams and its 25 miles of shoreline while hikers, mountain bikers and climbers recreate in the scenic foothills surrounding the 6.5-mile-long jewel.
But Horsetooth Reservoir was never meant to be a recreational paradise…
Though it’s become the state’s third-most visited reservoir, Horsetooth Reservoir’s main mission from the beginning was to provide water for agricultural fields on the Eastern Plains and increasingly thirsty Front Range cities such as Fort Collins.
That mission started 71 years ago on Jan. 10, 1951, when water diverted from the Western Slope began flowing into Horsetooth Reservoir as part of the massive Colorado-Big Thompson water diversion project.
Much has changed at the reservoir as well as in surrounding area since then.
In 1951, Fort Collins’ population was about 15,000 and an acre-foot of Horsetooth water sold for $4.50…
Today, Fort Collins’s population is about 174,000 and an acre-foot of Horsetooth water goes for $100,000.
In the beginning, 99% of the water went to agricultural fields and 1% to cities.
Today, that split is closer to 50-50, which is about the split Fort Collins takes from its two water sources — Horsetooth Reservoir and the Poudre River.
Here is a short history lesson of Horsetooth Reservoir’s humble beginnings, gathered from historical books, newspapers and water manager Northern Water.
Horsetooth history starts out dry
The area under what now is Horsetooth Reservoir was once where part of a town by the name of Stout was located.
Back in the day, Stout was the center of a large sandstone quarry from which deliveries still grace buildings from Fort Collins to Denver to Omaha, Nebraska, to St. Louis. They were even used in Chicago’s World’s Fair buildings.
Remnants of the once flourishing town (now the Horsetooth Heights subdivision) are visible at the south end of Horsetooth Reservoir.
Decades after the sandstone market dried up, the thirst for a consistent source of water for agricultural fields and growing cities emerged and the Colorado-Big Thompson water diversion project was born.
It entails a series of pump plants, tunnels, pipelines and canals that move more than 200,000 acre-feet of water per year from the Upper Colorado River basin to Lake Granby and Shadow Mountain Reservoir in Grand County before pumping it to the Front Range.
The project consists of 12 reservoirs, 35 miles of tunnels and 95 miles of canals, with the 13.1-mile long Alva B. Adams Tunnel beneath the Continental Divide serving as the key to the entire project.
As part of that project, four dams and a dike were used to wall off canyons just west of Fort Collins for Horsetooth Reservoir, which is the project’s largest Front Range reservoir.
Horsetooth Reservoir timeline
Here is a timeline on the history of how Horsetooth Reservoir came to be, gathered from historical books, newspapers and Northern Water:
1870: Irrigation history begins in Northern Colorado with the Greeley colony serving as the epicenter.
1881-82: Greeley, Salt Lake and Pacific Railroad Co. (Union Pacific) builds a rail line connecting the quarries at Stout to Fort Collins, Greeley and Denver. A trestle that bridged Spring Canyon and where a dam is now located was the largest of the 32 bridges at 262 feet long and 45 feet high.
1883: Stout boasts a population of more than 900.
1884: State engineer E.S. Nettleton conducts the first preliminary survey of a possible diversion project to import Western Slope water to the Front Range.
1893: The heyday of the stone quarry has passed, but some quarrying lingers.
1900: Stout is a ghost town.
1908: Stout post office closes.
1933: Discussion of what will become the Colorado-Big Thompson water diversion project begins amid the Dust Bowl.
1936: Congress officially renames the Grand Lake Project the Colorado-Big Thompson Project.
1937: Northern Colorado Water Conservancy District forms to build and manage the C-BT project. It is now called Northern Water.
1937: Congress approves $900,000 to build the C-BT project.
1938: C-BT construction starts. Cost of the project is about $160 million.
1940: Construction begins on the Continental Divide Tunnel (later named the Alva B. Adams Tunnel) with one crew beginning from Grand Lake on the Western Slope and a second team tunneling from a location near Estes Park. When complete, the tunnel is the longest ever built from two separate headings.
1942: CB-T construction halts due to World War II.
1943: CB-T construction resumes.
1944: The two tunnel crews meet after tunneling through the Continental Divide. NBC radio broadcasts the event live to the nation. A check of the center line and grade reveals the two sides are off by the width of a penny.
1946: Gravel road (Larimer County Road 38E) is built around the south end of Horsetooth Reservoir to Masonville to aid in construction of the reservoir.
1946-49: Construction of Horsetooth Reservoir takes place at a cost of $20 million for the reservoir and canals.
1947: First CB-T water is delivered to the Front Range.
1951 (Jan. 10): First water starts spilling into Horsetooth Reservoir.
1951 (July 21): First water releases from Horsetooth Reservoir were made to the Poudre River. An estimated 500 people line the railings for the release ceremony at the Horsetooth outlet canal at the north end of the reservoir.
1954: Larimer County assumes management of recreation at Horsetooth, Carter Lake and Pinewood Reservoir. Recreational fees that year generate $1,200.
1954: Proposal made for a road along the east side of Horsetooth Reservoir from Horsetooth Dam on the north to Soldier Canyon Dam on the south. It would later become Centennial Drive.
1956: Horsetooth Reservoir reaches full capacity.
1967: Colorado Game Fish and Parks (today’s Colorado Parks and Wildlife) purchases the 2,300-acre Howard Ranch, which became Lory State Park in 1975, on the west side of the reservoir.
1972: Annual fees at Horsetooth Reservoir include $12 for boating, $5 for vehicles and $2 for a three-day pass. Fees expected to generate $70,000.
1973: First major improvements at reservoir include 75 parking spaces, 125 campsites and four boat-in campsites and new toilets completed mostly in what now is the South Bay area.
1976: A July flash flood on the Big Thompson River kills 145 people and causes more than $35 million in property damage. Flood water and debris destroy the 240-foot-long Big Thompson Siphon (visible at the mouth of the Big Thompson Canyon), halting C-BT Project water deliveries to Horsetooth Reservoir.
1977: Drought hits northeastern Colorado, resulting in Horsetooth Reservoir reaching its lowest level since it was first filled at 15,240 acre-feet. The current capacity is 156,735 acre-feet.
1980: An estimated 200,000 visitors come to Horsetooth Reservoir.
1981: Larimer County purchases the 2,100-acre Soderberg Ranch for $3 million. The site would become Horsetooth Mountain Park just west of the reservoir.
1983: BLM predicts that if one of Horsetooth Reservoir’s dams failed, a 30-foot wall of water would rush toward Fort Collins, reaching CSU, the Poudre River and Interstate 25 in less than hour, Timnath in two hours, Windsor in three hours and Greeley in five hours.
1986: Horsetooth Rock Trail to the top of Horsetooth Rock is completed.
1987: About half of the two roads along the south and east sides of the reservoir are paved.
1988: Proposal to turn Horsetooth, Carter and Pinewood reservoirs and Horsetooth Mountain over to the state to become state parks dies.
1988-89: Horsetooth Reservoir’s Horsetooth, Soldier Canyon, Dixon and Spring Canyon dams raised 3 to 8 feet, increasing the reservoir’s ability to store water from major flood events and address safety concerns. It had been discovered in 1984 that the original dam faces had settled 3 feet. Cost of the project is $1.8 million.
1992: In February, a 9News helicopter crashes into the reservoir in heavy fog, killing two people and leaving pilot Peter Peelgrane, 46, fighting for his life.
1992: Horsetooth Falls Trail is built.
1996: First flush toilets installed at reservoir.
2001-03: Northern Water Conservancy District (now Northern Water) and the U.S. Bureau of Reclamation work to modernize Horsetooth Reservoir’s four 50-year-old dams to make the structures more earthquake resistant and reduce seepage. Cost of the project is $77 million. The work required the water level to be reduced by 70 feet to to “dead pool” storage — about 7,000 acre feet, or roughly 5% capacity.
2021: Construction of the 90,000-acre-foot Chimney Hollow Reservoir begins west of Loveland with completion of the project expected in 2025. It’s Northern Colorado’s first new reservoir in about 70 years and is expected to relieve some of the recreational pressure from Horsetooth Reservoir.
