Last month, I stepped into the John Day River on an early Saturday morning. The canyon walls in the distance glowed gold, and parts of the river’s surface looked like glass except where soft seams met the faster current. Before I even stripped the line off the reel, I looked up river and spotted a gentle bubble line sliding along a semi-submerged boulder and into a slow, emerald pocket. If I were a bass, I’d live right there. 

I observed and learned that both Mark Meyer and Jane Trafallis both fished that area prior. I decided to walk up to that part of the river. I put on my sunglasses and looked more closely into the water. Sure enough. I saw about a half dozen small mouth bass swimming below the surface. A few casts later, after switching to a smaller olive-colored wooly bugger, a little smallmouth bass confirmed what my eyes were seeing. I hooked one! It was the first of 24 fish, which Kelsey and I caught that day. What a fun trip!

Moments like that remind me that one of the most valuable skills in fly fishing has nothing to do with casting distance or perfect knots—it’s the ability to read water. Knowing where fish hold turns random blind casting into deliberate, targeted presentations.

Why Reading the Water Matters

Fish don’t choose their spots by accident. They’re constantly balancing three needs: food, oxygen, and safety. Water that provides all three becomes a prime holding zone. The better you can identify those areas, the more productive your time on the river will be.

Current and Structure

Current is the lifeblood of a river. It delivers food, determines oxygen levels, and creates shelter. As you approach a stream, start by looking for:

• Seams: Where fast water meets slow water. Fish often hold just inside the slower side, ready to dart into the seam for food.
  
  

• Riffles and Runs: Riffles oxygenate water and deliver a steady supply of insects. Runs below riffles often hold hungry trout.
  
  

• Pools: Deep pools offer safety and a break from strong current, especially in warm weather or winter.
  
  

• Obstructions: Rocks, logs, and undercut banks create microcurrents and protection from predators. Fish conserve energy behind structure where current is soft but food drifts by.

The Three Essentials

When scanning a river, ask yourself: Does this spot offer food? Oxygen? Safety?

• Food: Bubble lines and drift lanes are conveyor belts for insects.
  
  

• Oxygen: Fast, choppy water is well-oxygenated, critical in summer heat.
  
  

• Safety: Deep water, overhead cover, or broken surface tension gives fish confidence to feed.
  
  

If a location checks all three boxes, you’ve found a prime target.

Surface Clues

Sometimes the river tells you exactly where to cast—you just have to listen. Watch for:

• Rises: Obvious, but not always as they seem. Rings in soft water often indicate sipping fish. Subtle bulges without splashes can reveal big trout feeding just under the surface.
  
  

• Bubble Lines: They mark the main food conveyor belts. Casting into a bubble line often produces faster results than random drifts.
  
  

• Surface Tension: Slicks and gentle glassy pockets often hold fish because they mask movement and offer calm feeding lanes.

Season and Flow

Fish behavior shifts with the calendar and the river’s condition.

• High Water: Fish move tight to banks or into soft eddies where they can rest.
  
  

• Low Summer Flows: Seek out deeper runs and shaded pockets.
  
  

• Cold Weather: Look for slower, deeper water where fish conserve energy.
  
  

• Hatches: When bugs are coming off, fish often move into riffles and tailouts to feed aggressively.
  
  

Small Water vs. Big Water

A tiny mountain stream might only have a few prime lies per pool, while a broad river like the John Day or Deschutes can offer dozens within a single run. On small water, stealth and precision are critical. On big water, breaking the river into “lanes” and fishing each methodically is the key to covering ground effectively.

Practice Observation Before Casting

One of the best habits you can develop is to pause for a full minute or two before you even unhook your fly. Watch the current. Look for seams, bubbles, and subtle rises. Imagine where a fish could sit with the least effort and the most reward.

On group outings, it’s fun to practice together. Before stepping in, perhaps have everyone point out where they think the fish are and explain why. It sparks great discussion and often reveals how differently we all read the same water.

Bringing It Together

Reading water is part science, part intuition, and part time spent observing rivers. The more you practice, the more second-nature it becomes. Soon, you’ll find yourself spotting fishy water while driving over bridges or hiking past streams.

The next time you approach a river, remember: don’t just rush to cast. Take in the current, the structure, the clues on the surface. When you can see the river the way a fish sees it, every cast becomes more intentional—and more rewarding.