Hebgen Dam Malfunction Effects on the 2022 Fly Fishing Season

Posted on December 3rd, 2021 in Area Fishing News, Season Forecasts, Weather & Water Conditions

As many readers will know, Hebgen Dam on the Madison River malfunctioned the morning of November 30. In this post, we give a summary of the problem, immediate efforts to rescue stranded fish, and impacts. We then make some guesses on the effects of Hebgen Dam malfunction on the 2022 Montana fly fishing season.

Summary of the Hebgen Dam Malfunction

Around midnight on Tuesday the 30th, a dam component broke and caused the dam’s outlet gate to immediately shut. This Hebgen Dam malfunction reduced the river’s flow from just under 700cfs to under 200cfs (half the record low flow) in about 30 seconds. Imagine the latch that keeps an extendable ladder extended suddenly breaking and the ladder collapsing abruptly to its folded length.

madison river flow graph

Madison River flow graph showing the abrupt drop (and recovery) in flows.

This abrupt cut in flows did not leave time for fish (trout and forage both) in side channels and other shallow areas to flee to deeper areas and left brown trout redds full of fertilized eggs from the recent spawn high and dry. Here are more details on the problem. Repairs on the dam were completed just after midnight on Thursday December 2, meaning fish in side channels were trapped and eggs left exposed for about 48 hours. The impacts were highest between Hebgen and Quake Lakes, where the drop in flows was most abrupt and only a couple tiny tributaries enter to keep flows slightly higher.

dry madison river

The channel at left is usually a couple feet deep and is full of brown trout redds.

On Wednesday December 1, volunteers coordinated by Montana FWP staff conducted a salvage operation to move fish trapped in deep spots in cut-off side channels to the main channel while avoiding redds that were still damp. Most fish moved were sculpins and some small trout. Most dead fish found were small trout. It seems that most larger trout were already in deeper water (typical for winter water conditions) or were strong enough to wriggle over the shallow gravel while it still had any water at all flowing over it. That said, the largest trout rescued were over 24 inches in length.

Immediate Impacts

Despite the above efforts and the relatively short period before flows returned to normal, a fish kill of unknown proportions is certain. Additionally, a substantial loss of the 2021 brown trout spawn is also certain. The worst fish kill seems likely to have occurred immediately below the dam. The worst egg loss is likely the entire section between Hebgen Dam and natural Quake Lake downstream. Both impacts gradually decrease the further downstream you travel, with the trout kill in particular much lower by Cameron, Montana, about halfway between Quake Lake and Ennis Lake. Impacts on redds are likely present throughout the Madison between Hebgen Dam and Ennis Lake.

Several factors probably help reduce the overall impacts of the dam failure:

  • The weather: It has been extremely warm in Montana lately. This means that most isolated side channels did not freeze overnight, even at the surface. In effect, the side channels cut off from the main river were briefly turned into shallow ponds in which fish were trapped. While stressful, since these areas did not freeze, most fish trapped in the deep spots in side channels did and will survive.
  • The season: Most fish, adult trout in particular, were already in winter holding areas of deep areas of the main channel or – in the case of fish “Between the Lakes” between Hebgen Dam and Quake Lake – down in Quake Lake. Compared to summer, when many fish move into side channels to get out of heavier currents in the mainstem and/or to feed, many fewer fish were trapped.
  • Prompt and massive recovery efforts: A huge turnout on Wednesday December 1 from Ennis, West Yellowstone, and Bozeman fishing guides, anglers, and concerned locals to help FWP relocate trapped fish meant that many fish, particularly trapped sculpins, were moved to safety in the mainstem. So many volunteers turned out that many were not required to join recovery efforts since all publicly-accessible areas were covered.

Montana FWP instituted an immediate emergency fishing closure on the entire Madison River from Hebgen Dam to Ennis Lake when notified of the crisis. To our surprise, this closure was lifted as of Friday, December 3. We expected it would be continued for quite some time and honestly are a bit horrified that it was lifted.

We encourage all anglers to AVOID this stretch of the Madison through the winter and spring months to allow the fish time to recover and to ensure no angler impacts on remaining brown trout redds and the upcoming rainbow trout spawn. The lower Madison near Bozeman is below Ennis Lake and was unaffected by the dam malfunction. The Yellowstone Park section was likewise unaffected.

Volunteers rescuing trout and sculpins on the Madison River

Volunteers rescuing trout and sculpins on the Madison River. Photo by Washingtonflyfishing.com message board member (and Bozeman-area local) user “Swimmy.”

Effects of the Hebgen Dam Malfunction on the Madison River

Effects on the Madison River itself remain to be seen but are likely to be substantial and last through the 2022 season and beyond. These impacts will be highest between Hebgen and Quake Lakes and lowest between Varney Bridge and Ennis Lake. The lower Madison River downstream of Ennis Dam (including the Beartrap Canyon) will be unaffected since Ennis Dam had normal water releases during the crisis.

Likely effects include:

  • Slightly reduced overall trout counts: While the overall fish kill is probably not as bad as initially feared, some trout certainly died after their holding areas dried up and others will die because of the immense stress they underwent between suddenly being trapped in shallow, exposed areas and the stress of being trapped and moved to refuge in the main channel. Immediate fish kills will be concentrated on smaller trout and sculpins, while stress-related mortality will be heavier among larger trout.
  • A substantial loss of the 2021 year-class of brown trout: While not a total loss, we expect the 2021 brown trout spawn to be a disaster, especially in the “Between the Lakes” stretch and probably down to Lyons Bridge. This loss will be more and more apparent as time progresses and this year’s eggs reach catchable and then spawning size. Another poor spawn is likely in about 2026 since fewer spawning-size brown trout will be present. This impact comes on the heels of an unexplained reduction in brown trout numbers across SW Montana that has occurred over the past several seasons.
  • Reduced sculpin populations: Sculpins are big trout food and there will be a lot less of them in 2022. Maybe the trout will eat flies better? Maybe they’ll shift more to stoneflies or smaller forage? Maybe they’ll just be skinny?
  • Reduced insect populations: Almost all insects trapped in channels that went dry will have died. Like the sculpins they should bounce back quickly, but see above about potential impacts to the trout.

When the Hebgen dam malfunction first occurred, we anticipated widespread and long-term angling closures on the river. At the moment, it does not seem that these will be instituted. We believe some closures SHOULD take place. We will be writing a letter to Montana FWP as a permitted outfitter on the river and thus a stakeholder suggesting as such. We believe:

  • The Madison should be closed between Hebgen Dam and Ennis Lake from now through the third Saturday in May, 2022 to give the fish a break and to allow an unimpeded rainbow trout spawn.
  • The Madison should be closed either between Hebgen and Lyons Bridge or between Hebgen Dam and Ennis Lake from October 15, 2022 and the third Saturday in May, 2023, to allow unimpeded brown and rainbow trout spawns.

The above changes would allow populations to return to normal for the future without unduly hurting area anglers and guides. Note that the traditional season opener from Quake Lake to Lyons Bridge was historically the third Saturday in May. This date was only changed about five years ago.

Effects of the Malfunction on Other Waters

We must first note that the “Between the Lakes” and “Fifty Mile Riffle” sections of the Madison River impacted by this disaster are not in our core operations area. In fact we are not authorized to guide between Hebgen Dam and Quake Lake and only run about one or two trips per season between Quake Lake and Ennis Lake. So the direct impacts of the Hebgen Dam malfunction, fish kill, and damage to the brown trout spawn on our operations and most of our Livingston-based clientele will be nonexistent.

Impacts on other waters will not be direct. Even the Missouri River of which the Madison is a source was and will remain unimpacted, since Ennis Lake downstream had normal water releases into the Missouri downstream.

Indirect effects may be present. These are all “possibilities,” rather than certainties:

  • Increased guide traffic on other waters: With reduced fish numbers on the Madison, many Bozeman-area guides may opt to float the Yellowstone River instead. Other waters like the Gallatin, Ruby, Jefferson, or other stretches of the Madison may see similar changes for a year or two.
  • Reduced angler traffic to the region overall: A small but noticeable drop in visiting anglers occurred on the Yellowstone River due to oil spills FAR downstream that occurred several years ago. These oil spills had no impact whatsoever on the Yellowstone as a trout fishery since they occurred far downstream, but bad publicity is bad publicity.  A few visitors may stay away because of this.
  • Widespread regulations changes to protect spawning trout: With proposals already being floated to reduce angling pressure during the brown trout spawn due to the aforementioned reduction in brown trout numbers region-wide, it’s possible FWP will implement widespread October-spring closures to protect this spawn not just on the Madison, but on most rivers.
  • Increased oversight of public utilities: Let’s hope… This isn’t the first time Hebgen Dam has failed, a pipeline has ruptured, sewage has been dumped directly into rivers, etc. etc.