CHAFFEE COUNTY — The fancy word is “anabatic.” It’s from the Greek.
For the rest of us, “upslope” will do. It means pretty much the same thing: good fishing.
It pays to be a weather watcher in Colorado, especially as a fisherman. The heat of a summer afternoon, the onset of monsoon season and the direction of the wind all factor into the sometimes-complex equation of where and when to catch fish. Then, of course, there’s the prevailing circumstance plainly known as drought.
There’s no escaping the reality in this fourth week of July. Colorado’s second consecutive has its clutches on the state’s rivers and reservoirs, where water temperatures are soaring into the 70s and and outright fish kills.
If there’s a silver lining to the scenario, it’s found in Colorado’s close proximity to the clouds. High in the mountains, the weather remains cool, intermittently overcast, with fish that have never known the stress of a heat wave. And like so many fishermen, they have never heard of anabatic winds.
Not that the name matters. It’s the outcome that makes the impact.
“Anabatic wind is the updraft wind that loads lakes up with terrestrials, dropping them with cool air over the lakes,” said Stuart Andrews, a guide out of the (719-395-1796) who specializes in high-country lake fishing. “It depends on what’s on the move, but sometimes there’ll be tens of thousands of flying ants, spiders, lady bugs, small grasshoppers. Fish will key on them and just graze like cattle on the surface. That’s when it really gets fun up here.”
The late Gary LaFontaine is the guy many fishermen credit for first noticing the phenomenon, or at least writing it down. In his ,” he wrote: “One of the secrets of mountain lakes is that the vertical winds, not horizontal ones, deposit most of the food on the water. The other secret is that trout on these lakes, given a choice, prefer to feed on the surface.”
The reasoning works something like this: On a typically warm July afternoon, the anabatic winds are driven up a mountainside as the sun heats the air just above it. As the hot air rises, it pulls up air from cooler valleys and shady groves, where insects linger. They will get sucked up in the wind, until something — like a lake — causes the air to cool again.
“The organisms fall vertically, like rain from the sky,” LaFontaine wrote. “The insects fall because of the uneven mixing in the atmosphere. In the swirling air currents, some gusts reverse into downslope winds, and wingless or weak-flying organisms are at the mercy of thermal variations. A lake is a heat sink, much cooler than the surrounding land by later afternoon on a sunny summer day. This explains why so many creatures drop onto the water.
“With terrestrial insects dropping from the sky dependably and predictably on warm afternoons, high mountain lakes suddenly start to look like dry-fly paradise.”
Paradise can be difficult to come by in a heat wave, especially for those among us with a penchant for fishing moving water. But aside from the cold tailwater depositories directly beneath dams, finding suitable river conditions at the moment can be challenging. Wildlife managers are asking anglers to refrain from fishing popular rivers such as the Colorado and Roaring Fork in the afternoons, when water temperatures are on the rise and cold-water species are under duress.
Even warm-water Front Range fisheries have seen the action slow in the summer heat, offering a convenient excuse to head up high and ply the still water.
“Lake fishing fascinates me,” said of Lyons. “I can’t remember who it was that said: ‘In a river the water moves and the fish stand still. And in a lake, the water stands still and the fish move.’ That’s the only difference. Everything else is exactly the same.”
Until it starts raining bugs.
