This is where the real work happens. Every time the water character changes around you, it's worth asking whether your current depth setting still makes sense.
Riffles
Riffles are typically shallow, fast, and broken at the surface. Fish hold near the bottom where the current is reduced, often tucked behind rocks or in pockets. Because the fast surface current moves your indicator quickly, you need your flies to get down fast. This usually means running closer to the bottom of the riffle than a formula suggests. In a riffle that looks one foot deep but has significant current, your flies need to be down in that bottom six inches. Set your indicator to put the flies just above the bottom structure, not halfway through the water column. Fish in riffles are not going to rise through fast current to eat a fly hanging above them.
Runs
Runs are the textbook water type where the 1.5x rule performs best. Depth is moderate and somewhat consistent, current is steady, and fish are often distributed through the middle and lower portions of the water column. A starting depth of one and a half times the estimated depth is a reasonable hypothesis here. This is the one place where the formula earns its reputation.
Pools
Deep pools require the most significant adjustment. Water depth increases sharply, current at the surface slows, and fish settle near the bottom, particularly near structure. The indicator may need to be extended well past the depth formula to get flies into the feeding zone. In a pool that's four or five feet deep, fish may be holding within a foot of the bottom. Your flies need to get there. Don't be timid about extending the indicator farther up the leader in pools. The current is slow enough that you can fish longer leaders without the rig becoming unmanageable. Shallow settings in pools are one of the most common reasons anglers drift through productive water without a touch.
Seams and Eddies
Seams are where faster and slower currents meet. They're productive because food concentrates there, but they create a specific challenge: the surface current and the current a few feet down can be moving at different speeds, even in different directions. This affects how your flies ride relative to the indicator. If your indicator is sitting in the fast lane and your flies are in the slower water, the indicator is going to drag the flies rather than let them drift naturally. Setting your depth slightly shallower in seams can help reduce this problem, but the more important fix is managing the mend to reduce drag. Eddies carry conflicting currents even more dramatically. The circular flow in an eddy means the current near the bottom may be moving in the opposite direction from the surface. Depth alone won't solve eddy fishing, but starting shallower and watching carefully for drag is the right approach.
Slack and Slow Water
Slow water is deceiving. Because there's less surface current, it looks easier to fish than faster water. In practice, fish in slow water have more time to inspect your fly, drag is immediately obvious, and flies sink more freely because nothing is pushing the rig. In slow water, you often need to shorten the depth setting from your riffle or run starting point because the flies will sink more freely on their own. If you carry the same depth into slow water that worked in a run, the flies may land on the bottom and stay there, producing no drift at all.
