Reading water Fly Fishing with Nymphs

Reading Water for Nymph Fishing

You get to a new river and have a basic idea of the style of nymphing you want to try. You think, today feels like a great day to work on indicator nymphing. So you build your leader, tie on your flies, and set your indicator to what you feel is a good starting depth.

Now, you’re standing on the bank looking over a run you want to fish. The stream is dotted with boulders and the current alternates patches of swift and slow classic pocket water. You know fish are hiding in there somewhere, but where. There seems to be at least a hundred places to cast. The question is, where do you start and how do you approach the water so the fish see your flies without seeing you?

Then you make a wise choice: Instead of jumping in a casting away aimlessly, you walk up the bank to gain a higher vantage point to survey and read the water. You study what the current is doing and identify several likely fish holding pockets. Now that you know where the fish likely are, you have a vague idea of a casting strategy and are ready to start picking apart the water cast by cast until you start hooking fish.

Making an Educated Guess About What’s Below the Surface

The problem with reading the water for nymphing is that you never really know what the fish are doing down there. When a hatch is going strong and you can clearly see what bugs are emerging and where the trout are sipping them in, your fly selection and presentation options are relatively straightforward tie on a dry fly that closely resembles the naturals and focus on upstream dead-drift presentations. But when you’re nymphing and no hatch is happening making an educated guess about what the trout are eating and where they might be holding is really your only option.

Most Trout Streams Follow a Simple, Repeated Pattern of Riffles, Runs, and Pools


Luckily, the workings of a river the interplay between current and structure are not entirely a mystery. As water flows from high to low, streams take on a variety of shapes and features, most of which are relatively predictable runs follow riffles, pools follow runs, and riffles follow pools.

Of course, every river has its own unique shapes and characteristics, but you can generally count on most trout streams to follow the same basic pattern.

Trout Use Certain Features of a Stream and Avoid Others

Trout don’t use the entire stream. Certain stream features and water characteristics are more suitable for trout and once you have a basic idea of what these areas look like, you’ll have a quiver full of clues to help you find and catch fish in every new stream you visit.

drifting nymphs through a run
drifting nymphs through a run

Trout Favor Areas of Slow Water Next to Fast Water

Like all wild animals, survival is a trout’s primary goal in life. A trout’s survival depends on two things:

  1. Eating as much as possible
  2. Burning as little energy as possible
  3. Not getting eaten by a predator

Trout, being the efficient creatures they are, accomplish all of these survival tasks simultaneously by carefully choosing where they spend the majority of their time.

So what does a trout’s ideal holding location look like?

In short, it’s an area of slow current next to an area of faster current.

While this is an incredible simplification of complex trout behavior, most of the time it?s true.

Here’s why:

  • The slow water provides them an easy spot to swim, minimizing the amount of energy they need to maintain their position in the river.
  • These slow patches of water are typically created by some sort of structure which serves as protection from predators. As the current flows around a boulder, stump, log, or other prominent stream structure, depressions around the structure are formed creating small pockets of slow water. In some instances, the water slows down so much that it actually reverses direction in what’s known as an eddy.
  • The faster water next to the slow acts as a buffet line, delivering a constant flow of food that drifts down through the current.

In an optimal holding zone following these parameters, a trout can swim easily and stay protected by structure then dart out into the faster water to snatch up any food that floats by.

Your goal, then, is to find these places of slow water and drift your flies through the nearby faster water, hopefully catching the trout’s attention with your trout-food-imitating flies.

But what does that actually look like in action?

Three Stream Features to Look for That are Perfect for Nymphing

Now that we’ve covered the basics of general areas where trout will hold in a stream, let’s get a little more specific so you know what to look for when nymphing a new stream.

Areas of Oxygenated Water

In addition to food and shelter, trout also need clean, highly oxygenated water to survive. As water flows and crashes over rocks and other structure, it gets stirred up and infused with oxygen. And trout are often nearby.

The bottom line:

Pay close attention to waterfalls, riffles, and any other areas of turbulent water. Find a nice piece of slow water next to the faster turbulent water and you’ve essentially struck trout-gold.

Current Seams

Current seams are the areas where slow water and faster water meet. In most cases, this difference in flow rates creates a visible seam on the surface of the water. If there’s a current seam near an area of turbulent water, you’ll often see a line of bubbles, foam, and debris drifting through the seam.

Chances are, there are all manner of aquatic insects, worms, and other bugs drifting helplessly downstream in the seam below the surface. That’s exactly where you want to drift your nymph rig.

Shallow Water Near Deep Water or Vice Versa

Trout holding zones, in addition to following the principles we outlined above, are generally in the bottom portion of the water column, anywhere from 6 inches to 2 feet off the bottom. However, trout don’t always stay in the bottom zone and regularly make use of the entire water column to fill their bellies and evade predators.

Anytime you find an area in the stream that transitions from deep water to shallow water, try to fish your nymphs as close to the point of transition as you can. Sometimes trout will hold in the deep water then shoot up into the shallow water for a bite of food, but other times the opposite is true. The tail ends of pools are prime examples of this sort of holding location and should never be passed up.

How to Work A Run Without Spooking Fish

To minimize the risk of spooking fish, it’s generally best to start at the end of a run and work your way upstream. This way, when you kick debris while wading, it won’t flow through water you haven’t fished yet. Remember, you want the fish to see ? and hopefully bite your flies ? before they ever know you’re there.

If you’ve taken the time to read the water and identify where you think trout will be holding, don’t be afraid to fish the run hard. Drift your flies through every likely holding spot and always be ready to set the hook. The more time you spend reading water and catching fish, the more intuitive the act becomes. Use the tips in this article (chapter) to help you get started and don’t be surprised when you develop a sixth water-reading sense!

Sources and More Reading

Read this article about setting up a traditional nymphing rod. Setting Up a Traditional Nymphing Rig

Read about the recommended rods, line and reel for Nymph fishing and “High Sticking” in this article, The Best Nymph Fishing Rod, Reel and Line

Read about the different types of nymphing techniques in this article. Explaining the Different Nymphing Techniques.

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