Where to Fly Fish in the Fall (Southwest Idaho)
South Fork Boise River
Close to home you cannot ignore the SF Boise River below Anderson Ranch Dam. The water levels are at the river’s minimum flow, 300cfs, and the river is extremely wadable. But what makes fly fishing the SF Boise River a good place to fly fish during the fall is the end of the Mahogany Dun mayfly hatch and the beginning of the fall Blue Winged Olive hatch. You still can see Pale Morning Dun mayflies, caddis in the evening, and Flav mayflies. If the dry fly fishing is not working for you then the nymphing can be the best on the river in the Fall. At 300cfs all the trout are now pressed into the safest areas of the river. The SF Boise becomes really easy to read in terms of searching out spots on the river that should hold trout. Reading the river at high water can be difficult at best. In October right after the time change other fly anglers begin to leave the river early or stop fly fishing the river for the year. However, knowing that there is a great BWO mayfly hatch that will begin after 3pm is enough for me to show up late in the afternoon and come home at dark. There have been many years where I just do not fly fish the SF Boise until fall just for this reason.
North Fork Payette River 
The North Fork Payette River is a tailwater river born from the bottom of Cascade Reservoir Dam in Cascade Idaho. The stretch of river that is most fishable in the late summer early fall is the section upriver from Banks Idaho beginning at the railroad bridge where the river will move to the right side of the hwy. to just downriver of Smith’s Ferry Cougar Mt. Lodge restaurant right where the beginning of the canyon begins. It is this stretch of the river which is fairly close to Boise where the good trout fishing begins. The North Fork Payette River is a tailwater river and most of your daytime fly fishing will be nymph fishing.
The river bottom is full of boulders and the trout will lay among these boulders so it is imperative that your nymphs reach the bottom so they can drift through and around the boulders to where the trout are laying. This river can only be fly fished after the Dam manager at Cascade Reservoir turns the water levels down, this usually is around mid to end of September. When this happens the river flows are almost perfect for nymph fishing, and you should be there. Because it is extremely hard to fly fish this river at high water levels the trout that live in the river experience little or no fly fishing pressure.
I usually start of nymphing this river with a stone fly nymph or rubber leg nymph followed by a caddis larva or bead head mayfly nymph of some sort. The type of nymph you use plays little in your success in comparison to where you put you nymphs and the weight you have either in your nymphs or attached lead to your leader. Most fly anglers who fail on this river fail because of their inability to get the fly down to where the trout live. You should be fly fishing the river all the month of October.
The Malad River
The Malad River an hour and twenty minutes east of Boise is simply my go to river in the fall and spring. The Malad River is considered to be the shortest river in America. The trout fishing in this river is either good or great. All the trout that live in the Malad River are wild rainbow trout. What makes this river a good fall river is it is at the same elevation as the City of Boise. This means you can fish this river all through the fall, winter, and spring. What appeals to me the most about the Malad River is its constant flow all through winter. This is a spring fed river making the river a good place for some aquatic insects such as the Blue Winged Olive mayfly and the summer caddis. This river has a wonderful BWO hatch in the fall, size 20. This hatch can start around noon and last until 3 daily. This BWO hatch will last well into winter. On good weather days you can almost guarantee yourself some nice action. The Malad River is a river in which you can fly fish year round. Consult Idaho Fish and Game for any changes in the regulations.
The Owyhee River
Where do I begin when it comes to fall fly fishing on the Owyhee River? The fall blue winged olive mayfly hatch. The mahogany dun mayfly hatch. The ever present midge hatch. These are just a few reasons why you should be on the “O” in the fall. Oh yes did I mention the river is open all year to fly fishing? If these are not reason enough to be heading to the “O” in the fall, then you have been hiding under a rock for too long. Other anglers know this also and the river can become crowded with guys coming back to the Owyhee after the blistering summer heat is over. Hence the above rivers are a better choice to fish to avoid the crowd. I will fly fish the Owyhee in the fall, but I keep it in my mind as a river I will put on the top of my list for winter fly fishing.
Bruneau River
The Bruneau River is located south of Mountain Home Idaho and is about an hour from downtown Boise. Historically the Bruneau River has been a really good fly fishing river, particularly a nymphing river, during the fall months. However, the past spring of 2022, which also has been a good time to fish the river, the fly fishing was fairly slow. I have had extraordinary days fly fishing there. The reports coming back from spring 2022 was that the river was fishing slow. This can be attributed to the drought of 2021 where the water levels were low, and the water warmed up. To reach the Bruneau River, turn right at the town of Bruneau and drive right through town. Follow the signs turning left. You will have to open and close gates and the parking lot is public. A short walk to the river is required. Google Map is your best support on this trip. The part of the river we fly fish is just a mile or so up from its confluence into CJ Strike Reservoir.
