Runoff is the one time of year when a river tells you exactly where the fish are: they are wherever the current is not. Every trout in a blown-out freestone has moved out of the main flow and into the few feet of soft water along the banks, behind boulders, and in the eddies, because holding in the heavy current would burn more energy than the food coming past is worth. The fishing is not subtle, but it is very specific.
Reading runoff on the gauge
Snowmelt runoff has a shape. Flow climbs for weeks as the snowpack melts from low elevation to high, peaks, and then recedes over a period that is usually longer than the rise. Inside that curve there is a daily cycle: warm afternoons push the flow up through the evening and it drops overnight. The morning is nearly always lower and clearer than the evening.
Two numbers matter more than the flow itself. The first is direction: a river that is rising and getting dirtier is the hardest water of the year, and a river that is falling and clearing is some of the easiest. The second is clarity. A foot of visibility with the flow falling is fishable, and often very good. Six inches of visibility with the flow rising is a day to do something else. Every river page on this site links its USGS gauge; look at the week-long trend, not the number.
Rain on snow is the exception. A warm rain during runoff can spike a river far beyond its snowmelt curve in a few hours. If rain is in the forecast, stay off the big freestones.
Where runoff does not apply
A good deal of the West does not blow out at all.
- Tailwaters. Dam-controlled rivers are shielded from snowmelt unless the reservoir fills and spills. The Bighorn, Missouri, Green below Flaming Gorge, San Juan, Frying Pan, and Middle Provo are all fishable through May and June when their freestone neighbors are brown. Releases may go up during runoff to move water through the reservoir, so check the gauge, but the water stays clear.
- Spring creeks. Groundwater-fed streams like Silver Creek, Hat Creek, and the largely spring-fed Metolius barely notice runoff.
- Low-elevation and desert rivers. Rivers whose watersheds hold little snow, like the Salt, Verde, and Oak Creek in Arizona, or the lower Owens, run on a different calendar.
Edge water: the two feet that matter
On a freestone in full runoff, the river is effectively two feet wide. Fish the soft water along each bank, the slack behind every boulder large enough to break the current, the inside of every bend where the flow slows, the back-eddies that form below points, and the clear tongues of water where a small tributary enters. Flooded grass along a meadow bank is prime; trout will hold in a few inches of water there, feeding on drowned worms and dislodged nymphs.
The casts are short, often just the leader and a few feet of line, and the presentation is high-stick: rod tip up, line off the water, flies drifting down the seam between fast and slow. Work upstream slowly. You are covering pockets a few feet long, with a fish in each one.
Big nymphs and why they work now
High water rips stonefly nymphs and worms off the bottom by the thousand, and the Salmonfly and Golden Stone nymphs that will hatch in June are already crawling toward the banks, right into the edge water where the trout are. The charts here put Salmonflies at peak in June on 30 rivers, most of them Montana, Idaho, and Colorado freestones, and Golden Stones at peak in June on 60. Runoff is the nymph stage of those hatches.
The rig is heavy and short. A Pat's Rubber Legs or similar rubber-leg stonefly nymph, size 6 to 10, in black, brown, or coffee, as the point fly. A San Juan Worm, a Squirmy Worm, or a large beadhead Prince or 20 Incher above it. Enough split shot that you are hanging up now and then. A leader of 7 to 9 feet ending in 3X or 4X, because the fish are not leader-shy in a foot of visibility and you will be pulling flies out of sticks. A large indicator or a tight-line rig, whichever keeps you in contact.
Streamers in dirty water
A big dark streamer fished slowly along the edges is the other runoff method, and on brown-trout rivers it can outfish nymphs. Black, olive, or dark brown patterns with some bulk (a Sculpzilla, a Sparkle Minnow, an articulated sculpin) on a sink tip or with a heavy conehead. Cast tight to the bank, let it sink, and strip slowly and steadily along the seam. Fish in off-color water find the fly by vibration and silhouette, so a fly that pushes water matters more than one that flashes.
When runoff ends
The end is gradual and it is the best fishing of the early season. Watch for the gauge to fall for several consecutive days without the afternoon bump, and for the color to go from brown to green to clear. As the water drops and clears, the fish stay on the edges for a while and then spread back into the riffles and runs. The Salmonfly and Golden Stone hatches typically ride the recession, which is why late June on a Montana freestone can go from unfishable to the best dry-fly week of the year in ten days. What is hatching where at that point is covered on the June page.
The order in which rivers drop is roughly the order of their elevation and snowpack: Utah's lower valleys and Colorado's lower freestones first, then Idaho and western Montana, then the Yellowstone and the high headwaters last. In a heavy snow year every date slides later.
A runoff day, in order
- Check the gauge trend and the weather for rain before you leave. Falling and no rain is a go.
- Fish mornings; the water is lower and clearer before the afternoon melt arrives.
- Stay out of the main current entirely. Wade ankle to knee deep only, with a belt and a staff. High water moves rocks and logs, and a fall in it is a genuine emergency.
- Carry big nymphs, worms, a few dark streamers, split shot, and 3X. Leave the dry-fly box in the truck.
- Work every seam slowly and expect the fish to be in a foot of water.