One of the lucky side effects of dams is the creation of trout habitat in the tailwaters below them. The damming of rivers, and resultant cooling of the rivers below has added thousands of miles of trout stream habitat in the U.S. alone and has expanded the range of trout to parts of the country where trout were once unheard of.
Tailwaters create interesting ecosystems, not unlike large spring creeks in water chemistry and biology. Here are a few simple tips, some good bugs, and things to remember when fishing streams or rivers below dams.
1. Go small, especially close to the dam. The very cold water that comes from bottom release dams doesn't usually grow large insects. Some typical sizes are 24-16 for most dry flies
and nymphs. There are always exceptions but as a general rule, your size 12 attractor patterns are better left for free flowing river systems or a little warmer water far downstream.
2. Match bugs exactly. Tailwaters tend to produce large numbers of bugs so fish get very good at knowing what they are eating. Try to match the local insects in size and shape first, then get the color right too if you can.
3. Nymph fish first, then try dries. Many tailwaters produce large numbers of aquatic invertebrates that never turn into flying bugs. Scuds, aquatic worms, and sowbugs are often very abundant in tailwaters. With so much drifting protein, many tailwater trout never really need to grab anything at the surface.
4. Remember that tailwaters have different hydrology than other rivers. Some large hydroelectric dams vary their outflow according to energy needs, creating flows that fluctuate enormously, while some dams have very stable outflows, far more stable than a river formed by snowmelt or rainfall. It is wise to check with local fly shops and government agencies about what to expect out of the tailwater you plan to fish. You can check the current flows on our site here.
5. If regulations allow it, try your local tailwater during the winter and hot summer months. The water temperature of most tailwaters varies very little throughout the year. During the winter it will be warmer than everything else and during the summer it will be cooler. This makes it possible to fish many tailwaters at basically any time of the year.
Use local knowledge and good maps, or even simply Google earth or similar products, to locate a tailwater near you and you may just find out that there are year round trout fishing opportunities near you almost wherever you might be.