Highline Lake State Park

From October 1 through the last day of February, no motorboat runs on Highline Lake. The water is closed each year to give migrating birds a place to rest, and the waterfowl at times number in the thousands. Watchable Wildlife Kiosks stand on either side of the lake. They are accessible shelters fitted with viewing scopes. More than 200 bird species have been recorded in the park, among them snow geese, white swans, pelicans, blue herons, osprey, bald and golden eagles, sandhill cranes, loons, loggerhead shrikes, Cooper’s hawks, and the vermilion flycatcher, which CPW calls extremely rare in western Colorado. The National Audubon Society has named the park an Important Bird Area. At the north end of the lake are seven waterfowl blinds. Hunting is allowed only Monday through Friday, and only from those blinds.

Two lakes off 11 8/10 Road

The park covers 738 acres of high desert north of Loma in Mesa County. It is reached by taking Highway 139 north from Interstate 70 and turning onto Q Road and then 11 8/10 Road. The Visitor Center stands at the east entrance. Its store sells firewood, ice, worms, lures, and Powerbait. It also lends life jackets to anyone with identification, and children’s fishing poles and tackle boxes to an adult with a driver’s license. Along the walls are wildlife displays and paintings and carvings of the park’s birds, made and donated by volunteers. Colorado Parks and Wildlife runs the park, which has 56 campsites open year-round and 9.6 miles of trail. The Leave No Trace organization says the park serves nearly 150,000 visitors a year.

Highline Lake is the larger of the two lakes, at 160 surface acres. It is open to power boats, jet skis, water skiers, sailboards, and paddleboards from March 1 through September 30. On weekends from May through Labor Day it regularly fills to boat capacity, and trailers wait until another boat comes out. The wait can run past four hours. Weekdays and evenings rarely have one. Water skiing has its own rules: every boat travels counter-clockwise, carries an observer, and flies an orange flag. Wednesdays are wakeless, with boats held to about 5 miles an hour, except when July 4 falls on a Wednesday. Paddlers launch from the East Ramp near the Visitor Center and head for the coves and the quieter north end.

Lakeview Swim Beach is a buoyed area of Highline Lake open from the second weekend in May through the end of September. The water runs from the high 60s to the low 80s. It is the only place in the park where swimming is allowed. The park has 44 family picnic sites with tables and grills. Some sit on grass under mature shade trees. Others are cabanas on sand.

Mack Mesa Lake lies just upslope. It is the smaller and older of the two, open only to paddleboards, kayaks, and small boats with electric motors. No gasoline or diesel engine may be launched there, even with the motor off. It has an accessible fishing pier, is popular with shore anglers, and in cold winters is fished through the ice. Both lakes hold largemouth bass, black crappie, bluegill, channel catfish, and rainbow trout, and both are usually stocked in spring and fall. Largemouth bass are the only fish under special rules: an angler may keep two, and each must be at least 15 inches long.

Sage, cedar, and the Book Cliffs

The Highline Lake Trail is the main loop around the water, open to hikers and bikers. CPW lists it at 3.3 miles in one place and 3.5 in another. Shorebirds and mule deer are often seen along it. The Blue Heron Marsh Trail is a 0.6-mile loop through the riparian ground below the dam. It is flat except where it climbs back to the dam crest, and mule deer, raccoons, red foxes, and bobcats are seen there. The Greasewood Flats Loop smells of sage and cedar. The Mack Mesa Loop climbs to one of the highest points in the park. From there the Mack Mesa S Trail runs 0.6 miles of downhill turns, with views of the Colorado National Monument, Grand Mesa, and the Book Cliffs in Colorado and Utah. The East Bluffs Loop is a narrow singletrack with steep sections. Apart from a boat, it is the only way to reach the east-side cabanas and a pebble beach. Most trails are open to horses as well.

The ground between the trails holds mat saltbush, salt-cedar, prickly pear, and cottonwood. Rock squirrels, desert cottontails, prairie dogs, side-blotched and sagebrush lizards, and striped whipsnakes are about by day. Most of the park’s mammals come out only at night. The park says it lacks data on its reptiles and amphibians and asks visitors to log sightings on iNaturalist.

Older remains lie in the park as well. In the early 1900s the Uintah Railway at nearby Mack hauled dinosaur fossils bound for the Smithsonian Institution. Traces of the railway remain inside the park, and its artifacts are to be left where they lie.

The October 2026 calendar lists “Getting Batty,” a talk on Colorado’s bats, for October 10; a Trick or Treat Trail for October 24; and a guided moonlight hike for October 30. Each requires registration.

Water the canal could not use

Both lakes are filled with irrigation water. The Grand Valley Water Users Association diverts the Colorado River into the 55-mile Government Highline Canal to water more than 23,000 acres. Whatever the irrigators do not take spills into the lake. An August 5, 1951 story in The Daily Sentinel of Grand Junction made the case for using it: “Frequently, when there is insufficient demand for the Highline (canal) water, it must be wasted in washes. This is particularly true during and after rains.” The story proposed a small reservoir four miles north and one mile east of Mack, at the northeast edge of Mack Mesa, for warm-water fishing and as a refuge for ducks and other game birds. According to CPW, Grand Valley residents who wanted more water recreation built Mack Mesa Lake in 1952.

That lake drew enough use to start talk of a larger one in the Lower Valley. A February 12, 1966 Sentinel story reported that the Upper Highline Lake Dam had been recommended in the Game, Fish and Parks appropriation to the Colorado General Assembly. The estimated cost was $330,000. The new lake would sit just downstream of Mack Mesa so the two could be used together. It would take canal spill and runoff from an 11-square-mile drainage. Ground was broken May 15, 1966. The plans called for a lake nearly a mile long with 200 surface acres, behind an earth-filled dam 1,480 feet long at the top, 450 feet wide at the base, and 80 feet high. Total cost was projected to exceed $500,000. Planners hoped to have it ready for duck hunting that fall and for warm-water use by spring 1967. The dam stands on a tributary of Mack Wash, and its construction was completed in 1967.

A dam on shale

Water stored behind the dam in May 1967 had to be let out in June. According to a Sentinel story of July 28, 1967, it had seeped through the shale on both abutments. The seepage took away a chunk of road on the west side and cut a cave-like hole beside the right abutment. A $30,000 grouting job to plug the leak also failed. An April 14, 1968 story traced the seepage to sand lenses in the shale that anchored the dam. “As the water goes through the shale it dissolves salt and weakens the abutment,” it said. “If the situation is allowed to continue the entire east abutment of the dam could be pushed out.”

In the spring of 1968 the dam was considered unsafe. The leaks were at 40 to 45 feet, so the lake was held just below that level, and water skiing and fishing went on in the lower water. Repairs needed legislative approval, and then-Sen. Chet Enstrom introduced a bill for a $105,000 supplemental appropriation. In a July 23, 1969 story, state geologist John Rold conceded that the dam site should have been investigated more thoroughly long before the dam was planned and built.

The trouble continued in later decades. A parasite attacked the lake’s trout in 1971. In 1985 the soil layers deep under the west end of the dam settled. In 1989 the state began a long-term monitoring program on the dam. Piezometers, inclinometers, and survey monuments track water pressure and ground movement, and v-notch weirs and toe-drain pipes measure seepage. The State Engineer classifies the structure as a high-hazard dam. In 2014 the lake was lowered so crews could clear the head gate, which lay under 16 feet of sediment. They also hauled trash off the bottom, “motors and anchors all over the place,” as a Sentinel story put it.

The land along the park’s entire western boundary has belonged to the Long family since the early 1940s, when the present owners’ father bought it. The family grazed cattle on it and cut some irrigated hay. In 2021 CPW proposed buying the 174 acres for $775,000 to open public access to the lake from the west. In 2024 the West Entrance was moved to a new road off R Road. In December 2023 the park received the Leave No Trace Gold Standard Site designation, the first state park on Colorado’s Western Slope to earn it. “We owe our success to the dedicated volunteers who worked tirelessly alongside us, including the Friends of Highline Lake, Pomona Elementary, and Orchard Avenue Elementary,” said park ranger Howard Asal.

The mussel and the empty lake

On September 14, 2022, CPW staff found an adult zebra mussel during routine sampling. Highline Lake became the first body of water in Colorado classified as infested. Park staff called the find “sickening.” In March 2023 the state lowered the lake to expose its shorelines and treated it three times with EarthTechQZ, an EPA-registered mollusk-killer. In October 2023 more mussels turned up on buoys. In 2024 all motorized boating was closed for the season, for the first time since the 1960s, while staff applied more of the chemical. The Sentinel’s columnist called the mussels the biggest headache in the lake’s history. CPW finished draining the lake by November 18, 2024, and it sat empty for the first time in more than 60 years. That same year, testing found zebra mussel larvae in the Colorado River upstream, in the reach that feeds the canal. The National Park Service reports that the source of the infestation has not been determined.

Water from the Government Highline Canal began flowing back into the empty basin on March 31, 2025. CPW expected the refill to take 35 days or more. A few days into it, the gauge still read 0 feet, against a full elevation of 65. “It’s great to see water flowing into Highline Lake again,” park manager Alan Martinez said, “and we look forward to welcoming our water recreationists back for the 2025 boating season.” Every boat on a trailer is now inspected before launch and decontaminated with 140-degree water on the way out. Each leaves with a blue receipt showing it was last used on water with a known aquatic nuisance species. CPW samples the lake weekly, and the lake will remain classified as infested until it has five consecutive years with no sign of mussels.