Antero Reservoir Closes May 13, 2026 — Colorado's Trophy Mecca Disappears

Why Antero Is Closing: The Drought Story

This isn't routine dam maintenance. This is drought—the worst in 40 years. The South Platte Basin snowpack sits at 7% of normal. Colorado's peak snowwater equivalent arrived 40 days early in March, and the Front Range is now in emergency water conservation mode.

Denver Water owns Antero. The reservoir is 92,651 acre-feet at full capacity, but it's shallow—just 18 feet deep on average. That shallowness made it a trophy fishery (warm water, insane insect production). It also makes it a water-loss liability in a drought.

Antero loses roughly 5,000 acre-feet per year to evaporation—about 5% of the reservoir. In a normal year, snowmelt replenishes that loss. In 2026, there is no snowmelt. That 5,000 acre-feet is unrecoverable. So Denver Water is transferring it downstream to Cheesman Reservoir via the South Platte River. Cheesman is deeper, older infrastructure—it loses far less to evaporation.

This decision affects 1.5 million Front Range residents. Denver Water declared Stage 1 Drought on March 25, 2026, asking customers for 20% water-use reductions. Mandatory outdoor watering restrictions are in place. Antero's drain is one of several conservation measures, but it's a big one.

The bottom line: This is the third major closure in 25 years (2002 drought, 2015 dam rehab, 2026 drought). And it's going to be deep and long.

Timeline: The End of Antero (For Now)

⚠️ No official reopening date has been announced. Denver Water operates on a year-to-year basis depending on snowpack. The 2002 drought closure lasted five years.

Antero's Legacy: Why It Mattered

Antero's first dam was built in 1909. Denver Water acquired it in 1924. For over a century, it was the quietest, most productive trout reservoir in South Park.

The fishery thrived on shallow water and cold depths. The 18-foot maximum depth meant warm summers on top, trophy trout stacked at 60–90 feet below. Aquatic insects—callibaetis, chironomids—bred in epic abundance. Rainbow, brown, cutbow, and cutthroat trout grew fast and fat.

The state record cutbow came from Antero. 18 pounds, 8 ounces. 28.5 inches. Not a fluke. Regular 15–20-inch fish. 20-plus-inch trophies every season. Guides booked months out. Anglers drove two hours from Denver for a day on the water.

This third closure will test whether the fishery can recover again.

⚠️ Critical: New Zealand Mudsnail Warning

Antero tests positive for New Zealand mudsnails—an invasive species that can survive 50+ days out of water.

If you fish Antero before May 13, you MUST clean, drain, and dry all gear before using it anywhere else. This includes:

• •Waders, boots, and felt pads — rinse, drain thoroughly, dry in sun for 24 hours
• •Rods, reels, lines — rinse fresh water through all guides and mechanisms
• •Nets, boxes, tackle — immerse and rinse, then dry completely
• •Boat, motor, trailer — rinse bilges and compartments, dry hull

One mudsnail transferred to Spinney Mountain or Eleven Mile could establish an infestation. Clean your gear—period.

The Fish Salvage: CPW's Plan

CPW is not just letting the fish die. They're running an emergency salvage operation—the same method they used in 2015 when the dam had rehabilitation work.

After May 13 closes the harvest window, CPW crews will truck trophy trout from Antero to three destinations:

• →Eleven Mile Reservoir — closest, largest capacity
• →Spinney Mountain Reservoir — same basin, excellent habitat
• →Cheesman Reservoir — downstream, Denver Water infrastructure

This gives Antero's best fish a chance. The 20-inchers, the breeding stock, the genetics that built the fishery. In 2015, the salvaged fish thrived and helped rebuild the fishery. It should work again.

Where to Fish Now: Alternatives in South Park

South Park still has trophy water. Not all of it is open and accessible the same way, but there are solid options.

Fishing Antero: Techniques That Worked

If you fish Antero in the final week (through May 13), here's what worked all spring:

• Chironomid nymphsBlack, red, brown patterns under indicator. Size 12–16. Classic Antero year-round technique. Fish 20–40 feet.
• Callibaetis nymphsOlive patterns. 15–18. Abundant hatch spring/summer. Fluorocarbon tippet essential—Antero's water is clear.
• Olive leechesWoolly Bugger style, 2–3 inches. Slow strip or hang in current. Fish 30–70 feet.
• Streamers (fall)Streamer fishing for spawning brown trout takes over in autumn—but you won't get there before closure.

Access: Hand-launch only from the boat ramp. Waders strongly recommended for shore anglers. Elevation 8,900 ft—dress for cold.

Will Antero Come Back? The Recovery Question

Maybe. Maybe not for a while.

In 2002, a five-year drought closed Antero completely. It reopened in 2007, and the fishery rebuilt slowly. The salvaged fish and natural recovery created a productive system again. CPW's 2015 dam rehab closure lasted one year. The fish salvage worked. The fishery rebounded.

This closure depends on Colorado snowpack recovery. If the South Platte Basin returns to normal precipitation in 2027, Antero could begin refilling in late 2027. Fishing might resume in 2028 or 2029. If the drought persists—if 2027 is another dry year—Denver Water keeps the reservoir low, and you're looking at 2030 or beyond.

The CPW fish salvage gives the best fish a real shot at surviving in Spinney, Eleven Mile, and Cheesman. When/if Antero refills, those genetics can repopulate. The fishery could come back stronger.

But there's no guarantee. Sometimes these closures are permanent in practice. Sometimes a fishery takes a decade to recover. All we can do is fish the water that's still open and hope the snowpack returns.

Bookmark This. Check Again in 2028.

We'll update this page as:

• →CPW releases fish salvage results (species counts, where they were relocated)
• →Denver Water announces refill timeline or reopening estimates
• →First fishing reports come back (2029+, probably)

For now, fish Spinney and Eleven Mile. Both are excellent. Both fish better on most days than Antero did. And they're open.