Dams, as so often happen, ruin many trout streams in our country, particularly upper watershed projects where so-called flood control dams are built. On the other hand, large reservoirs that are built in warm water river basins create trout fishing in the tail-water below. This is due to the cold water releases of bottom reservoir water during the summer months, creating a year round habitat for trout. Some of our most famous tail-water rivers such as the San Juan River of New Mexico, the White River of Arkansas and the east coast's Delaware River all owe their fame to cold-water releases.

How does the average angler fly fish a river with big league dimensions? A river with 200-yard long rifts flowing into aircraft carrier-sized pools isn't what you would consider your traditional trout water. Even the most experienced angler can be intimidated by its size.

Typically fly-fishing becomes limited to fishing in pools below rifts where rising trout can be easily spotted. My home water of the Delaware River is a good example where most anglers limit themselves to fishing its quiet pools below long broken runs. I often hear fishermen, experts alike; say nymph fishing the Delaware is not effective and just plain futile to try.

This attitude is very wrong. What does a larger body of water have to do with fish not feeding on nymphs? The answer is absolutely nothing. Swift broken water in big rivers provides good cover for trout. When surface activity declines trout will frequent the fast pocket water in search of aquatic morsels. Most mayfly and stonefly nymphs inhabit this water type. Stoneflies, in particular, offer good nymph fishing opportunities throughout the season. Drifting a pair of stonefly imitations is an extremely effective way to catch trout. These under-fished sections of the river can be a fishing haven for the angler willing to probe its depths with nymphs.

Whether one fishes on top with dry flies or at the bottom with nymphs, natural presentation of the fly is the most important aspect in the success or failure of catching fish. To be a successful nymph fisherman in a large river system, the angler must know what requirements are necessary to present a nymph imitation in the most natural manner at the depth trout are feeding. This is no easy task since it requires using split shot with the ability to cast and control your drift in varying velocity and depths. It is these factors that discourage the most ardent anglers from nymph fishing a large river. Fishing with weight requires time and patience to learn before success is achieved. The angler willing to sacrifice the time away from his or her favorite pool and learn the fundamentals of river nymphing will be rewarded with exciting new experiences.

Tackle requirements for bottom fishing in expansive pocket water begin with a 9' to 9 1/2' rod for 5 or 6 wt. Line. The length and stiffness of a long rod provide better line control while allowing you to cast flies and lead shot. Double tapered lines work well with plenty of backing to land the big one. Always use floating lines as they provide good visibility and a high float. Stay away from sinking or sink tip lines because of their difficulty to mend in fast turbulent water.

Your reel can be any conventional single action fly reel suitable for the required backing and line weight. Most reels made today are rim control, which is a nice option to allow you to 'palm' the spool when additional control is needed in a tough situation.

Leaders should be 10' to 12' in length tapered to tippet strength suitable to the size of fly you are using. Short leaders do not work in deep, fast pockets. You may also need to go one to two sizes larger in rivers where trout are more aggressive. Fishing 'blind' in fast open water, particularly on the Delaware, often produce vicious strikes because trout must react quickly to your offering. Going light on tippet strength often results in busted leaders and lost opportunities.

The use of lead weight on your leader is the key to getting the fly at the bottom where trout feed on nymphs. In order to respond to the varying depths and velocity changes, it is necessary to carry a variety of sizes of shot so weight changes can be made as you fish changing conditions. More weight not only allows the fly to sink deeper, but also slows down the drift in heavy current flows. This is critical so the fly drifts naturally with the speed of the bottom current.

The transition of casting a dry fly to casting a weighted leader can be an awkward experience. Since we are looking for accuracy and control of the fly rather than distance, very little false casting is needed. The biggest mistake most anglers make is to try casting with weight in the same manner as casting a dry fly. This usually results in one tangled mess, producing frustration, and giving the angler reason to forget about nymph fishing.

A good way to help your cast with weight is by letting the current of the river load the rod for you prior to your forward cast. To do this you simply strip off about 10 yards of line from the reel and allow it to drift down river until the line is fully extended in the current. The rod is now loaded and ready for the forward cast. In a lob-like motion, cast the weighted line up-river, checking the rod at about ten o'clock after the power stroke. This enables the line and leader to turn over, allowing the fly to enter the water before the line. Continue casting this way until you are able to control and direct each cast where you want it. It is important that the fly enters the water first to ensure maximum bottom drift of your fly.

Once you have mastered the 'short line' casting technique, begin developing line control that is needed to present your fly in the most natural manner. This is accomplished by trapping the line against the rod handle with one or two fingers of your casting hand immediately after your forward cast enters the water. Elevate your rod as your drift begins toward you, using your free hand to strip the slack you are unable to control with the rod. This keeps you in direct contact with the fly during the course of the drift. Continue this short line technique until you have developed your skills that the nymph is drifting without drag in the bottom current. With a stealth approach, nymph fishing can be accomplished successfully this way in the open pocket water of any river.

Situations will arise when a longer cast is needed to reach a deep depression or seam in the river. Actually it isn't a cast at all but a series of 'casting lobs' to extend out your cast. This 'long line' technique is more difficult to master, but extremely useful for big water. A longer cast means more line will be on the surface that is subject to cross currents causing unwanted drag. In order to avoid unnatural movement of the fly, a mend must be incorporated in your cast to allow the line to drop up river of the fly. This is called a reach cast and is executed by extending the casting arm and rod up-river as the cast is in the air drifting toward the target. After the cast is made additional mending may be required to extend the dead-drift of the fly. To do this you must force the fly line with the rod tip to arc or belly above the fly. Continual mending may be necessary through the entire drift while your free hand strips in any unwanted slack.

Mastering both techniques will allow you to cover most runs in a large river. When you are ready to fish select a riffle that provides good cover. The main channel offers the best cover for many eastern rivers, whereas western rivers look for trout to hold along undercut banks and deep edges. When you eye your target begin with the short line technique. Trout will feed in close when not disturbed. Once you are satisfied trout are not there, begin working your fly further out utilizing the long line approach on the more distant targets. Cover as much water as possible without sacrificing line control.

Nymph fishing large tail-waters is not an easy technique to master. Fishing blind with lead shot in heavy current can be a frustrating experience. Be patient, take time to practice each step until you get the results you are looking for. If you can fish with someone who has nymph fishing experience, observe, listen, but most of all…. experiment. Soon you will be rewarded with the most exciting fishing a tail-water has to offer.

Lee Hartman is a Delaware River guide/instructor and owns Indian Springs Fly Fishing Camp on the Upper Delaware River in Hancock, NY. When not fishing the Delaware, Lee escorts anglers annually to world-wide fishing destinations. Lee can be reached through his web site at http://www.indianspringsflyfish.com