When you first looked at a river and the idea of learning to fly fish came to you, you were reading water. You were looking at the water and picturing your back cast coming forward and landing upstream of that friction-rounded boulder. You knew not that you had made a judgement of where a fish should be, just that it seemed right.
When I think of reading water I do it like this. If I lived in a place where there were cheeseburgers flying through the air in a unidirectional manner where would I stand? That would change as my mood and level of interest changed. If I were hungry I would stand in one spot, if I were not I would stand in a different area altogether. Welcome to the world of reading a river.
Tout will be in a lie. Lie is a fancy word for a spot. There are feeding lies, holding lies, shelter lies, and prime lies. Trout spend the most time in holding lies. These are breaks in current that offer some protection from predators where the fish can rest. Feeding lies are areas where a fish might be able to sit and grab a bunch of passing morsels that may get pinched down into a concentrated area. Shelter Lies seem obvious by the name, these lies are used to protect the fish from predators. They are normally used only if the fish is forced to abandon its holding or feeding lie. If a steady stream of food is added to a Shelter lie it is classified as a Prime Lie.
Go to a river and look at it and picture yourself under the surface, where would you go if you wanted one of those cheeseburgers flying past?
Let’s add hydrodynamics into the mix, imagine the cheeseburgers have to follow the way water goes around objects. Now you can picture what the fish have going. Behind certain objects will be an eddy or a still spot in the water. Think of an eddy as a “free space”- the fish get food within reach and a good bit of break from the current. An eddy will make a greater or less than shape on the backside of the object. Whether it is greater or less is dependent on the direction of water flow.
There are pools, deep open places in the water. Pools can have big boulders but normally a consistent hard bottom. Pools normally tail out into some sort of riffle. Riffles are generally not too deep- one to four feet with lots of smaller stones on the bottom. Riffles can quickly turn into runs as they get a bit deeper and wider.
Essentially from here all the rest of the water on the river is referred to as flats. Flats generally don’t hold fish. A river can also make pools in its bends because the water is forced to turn so it digs that section deeper over time and so don’t mistake those for flats. Anywhere that looks “too fast” for a fish to swim probably is not a great spot, but just outside of that is.
Remember you won't always want cheeseburgers. Other times you want two or three. My advice is try and look for the place that looks like the cheeseburgers would be the easiest to grab and cast to that first. Those will be the easiest fish to catch. Then continue on using the grabbing a cheeseburger method to break down the water. The hardest place to grab a cheeseburger often holds the biggest fish, but you decide what in your day of fishing will make you happiest.