SPRING 2023 RUNOFF

HIGH FLOWS

The Boise River experienced high runoff this spring with flows staying above 4,000cfs for 2 months and reaching “bank full” flows of 6,000cfs for 2 ½ weeks. High runoff is a healthy part of the lifecycle of a river as it helps clean the bottom of accumulated debris and improves trout spawning habitat by redistributing smaller gravels. On a naturally flowing Freestone river, high water refreshes trout spawning habitat with new smaller gravels from upstream, however, on a Tailwater river like the Boise River, these new smaller gravels get trapped upstream behind the dam (Lucky Peak) which keeps them from refreshing the trout spawning habitat below the dam, which is why BVFF and TU have been doing gravel augmentations in the Boise River.

At "bank full" flows, the Boise River does harvest some smaller gravels from the banks and islands which improves trout spawning habitat in some places. We will be able to quantify that this fall when we do our annual Brown Trout Redd Counting and Mapping project. It will be very interesting to see how the high-water event impacts brown trout spawning, but my expectation is we will see an increase in the number of redds on the Lower Boise River.  Watch for our Brown Trout Redd Surveys this Fall and come see for yourself!

GRAVEL AUGMENTATION

In February of 2023 BVFF added 15 cubic yards of spawning gravel on the inside bend of a side channel of the Boise River. On a normal runoff year we would expect most of the gravel to stay on that inside bend, but on a high water year like 2023 Mother Nature is going to relocate it downstream (Mother Nature knows what she is doing and is very good at placing it in locations that are suitable for trout spawning). The below photos show the gravel augmentation location at winter flows (250cfs), in May at 6,000cfs, and then in August at 650cfs. At 6,000cfs you can see water coming into the side channel across a wider area, but the river velocity is still significantly less than the main river channel and there are plenty of soft-spots behind the woody cover for trout to shelter.

GRAVEL RELOCATION

Flows on the Boise River recently dropped to 650cfs (a very fishable flow!!) and I walked the side channel to see where Mother Nature decided to relocate our gravel. The good news is that the gravel is still in the side channel and Mother Nature left it in good locations for trout to use for spawning! The figure below shows the side channel, the gravel augmentation location, and where new gravel has accumulated. It is impossible to identify our gravel from natural gravels, but I can say that there are significant new deposits of small gravel about 500 feet downstream of our augmentation-zone, below where the side channel has an “S Curve”. This is a typical location for the river to drop gravel as they like to drop it on the inside bend where water velocity is reduced, which is one reason why sinuosity is important to a healthy river (sinuosity is a measure of how many curves a river has). And because the flows were so high, some gravel was dropped above the normal summer high water mark, leaving a kind of “bathtub ring” in some locations. This bathtub ring effect can also be observed in the entry area of the side channel from new gravels being dug up from the water spilling over the banks.

WOODY COVER

As a part of our trout habitat improvement work on the side channel we worked with IDFG and the Boise Flood District to incorporate woody cover to give trout fry shelter (shown in the figure above and the photo to the right). Woody cover is just as important to improving the trout population as spawning gravel. Early observations this summer have shown some rainbow trout fry in the side channel and we hope to join IDFG on their annual Trout Fry Survey later this fall to see how the juvenile trout handled the high flows. The large pieces of woody cover that were anchored are still in place but some of the smaller pieces were carried away by the high flows and could use to be refreshed and anchored.

The high water event left some debris at the entry to the side channel and broke through the nearby New Dry Creek diversion dam, dropping the water level and reducing flows into the side channel. At 650cfs we are getting about the same inflows to the side channel as we did at 250cfs last winter. We will be doing some maintenance on the side channel in August to help clear debris to improve inflows and improve the woody cover. If you are interested please sign up for the event posted on our website. 

TERRAFORMING

Below are some examples of how Mother Nature “terraformed” the side channel and where she moved our gravel. There is now good spawning gravel in the S-Turns and the tail-out below that. Before high water there was a 100' long narrow trench with a bottom of large cobble. That trench is now filled with spawning gravel and is an awesome long spawning run!  Some of these locations are more suitable to rainbows to spawn at higher flows and others are perfect for brown trout spawning at lower flows.  We will continue to monitor the side channel for spawning activity and report what we see.

THANKS FOR THE HELP, MOTHER NATURE!

Please welcome BVFF member Johnny Rogers as the new Leave It Better Lead. He replaces Brian Martin who has moved into the role of BVFF president. Johnny has been a member since December of 2021 and has volunteered for many projects including river cleanups, Diane Moore Nature Center access, and Expo 2023 where he posed as Eddy Trout.

Johnny Filling The Net On The SF Boise 2023

The Leave It Better Lead is responsible for coordinating our Spring and Fall "Real" Boise River Cleanups, informing us of partner organization river cleanups on the Boise and Owyhee rivers, and assisting with the Adopt-A-Stream program through Snake River Waterkeeper.

Thank you, Johnny, for volunteering for this Conservation mission role! We're here to help in any way you need.

A bill to permanently protect fish and wildlife on Owyhee River Canyonlands was introduced by Oregon legislators on June 8th.  The bill is supported by a coalition of ranchers, native tribes, anglers, hunters, and conservation groups, and will protect approximately one million acres of fish and wildlife habitat.  This Trout Unlimited article describes the bill and the support that will be needed to get it passed.

Trout Unlimited has also released a short film, produced by the Owyhee Sportsmen Coalition on fishing the Owyee River, which can be viewed HERE.

With the Idaho General Trout Season Opener approaching, people are wondering when the Boise River System will be fishable. The Boise River Reservoirs (Lucky Peak, Arrowrock and Anderson Ranch) are managed primarily for irrigation and their objective is to capture the maximum amount of water in the reservoirs. They release water from the reservoirs as needed to capture the runoff and have “rule curves” they use to manage reservoir outflows. Looking at the Bureau of Reclamation Hydromet site you can see that the reservoirs typically reach their peak levels the 3rd or 4th week of June. This means the river flows below Lucky Peak and Anderson typically drop to their normal summer levels around that same time—a bit later on high water years.

Our Boise Tailwater rivers tend to come into shape quicker than the Freestone sections because of how they are managed. While the MF of the Boise will continue to run high well into July the SF of the Boise below Anderson Ranch and the Main Boise River below Lucky Peak will drop into shape quicker.

Here is a look at this year’s runoff flows on the South Fork, Middle Fork and Lower Boise Rivers compared to similar years of 2011 and 2019. Based on those years, the SF Boise will be running very high when the season opens and won’t drop to normal summer levels until early July. In 2011 and 2019 the Main Boise river dropped to normal summer flows by early July. This year we had more space in the reservoirs so it is possible that flows on the Lower Boise will stabilize a bit sooner in late June.

The rivers are running high and cold and are dangerous to wade. Do not attempt to wade the SF of the Boise River until flows drop below 600cfs this Fall. Same goes for the Boise in town. Make sure you check BVFF’s Local Waters page for the latest conditions, including streamflows, water temperature and reservoir/boat ramp levels.

This winter’s excellent snowpack is turning into runoff and our local rivers are running high. Spring runoff’s impact on river flows, both timing and magnitude, depends on whether the river is a Tailwater River (below a dam, like the Lower Boise River through town), a Freestone River (naturally flowing like the Middle Fork of the Boise River) or a Spring Creek (like Silver Creek). Spring river flows can be dangerous, so it is important to know the river before you venture out. Both the Lower Boise River in town and the South Fork of the Boise River become dangerous to wade when flows rise above 600cfs. Flows on the Owyhee below the dam have started to come up and with the reservoir filling should reach normal 200cfs flows this summer, which is a very wadable level. Checking river flows on BVFF’s Local Waters page is an important part of planning your fishing trip.

TAILWATER RIVERS

Our Tailwater rivers are primarily managed for irrigation and flood control and spring flows below the dam depend on both the snowpack and the reservoir carryover from the previous year. If you have a good snowpack but low carryover—like the Owyhee drainage this year—then you aren’t likely to have high river flows below the dam. But if you have a good snowpack and good reservoir carryover—like the Boise drainage this year—then you are going to see high spring flows.

Dam managers are currently draining water in the Boise reservoirs (Anderson Ranch, Arrowrock and Lucky Peak) to make room for our great snowpack. The Lower Boise River in town is running high and expected to flow at 5,000cfs to 6,500cfs through June. Flows like this are not uncommon, Figure-1 shows how often we’ve had high flows over the last 25 years, which includes 13 years over 5,000cfs and 9 years when we reached or exceeded “bank full” conditions (6,500cfs or higher).

The South Fork of the Boise River is also running higher than normal and we will likely see flows reach 4,000cfs – 6,000cfs in May with continued high flows when the season opens Memorial Day weekend, so make sure you check BVFF’s Local Waters page before you go.

High flows on a Tailwater river tend to happen earlier in spring in order to make room in the reservoirs for the anticipated snowmelt. It is a calculated game of letting out just enough water to avoid flooding while capturing the maximum amount of water in the reservoirs. They are pretty good at managing flows to avoid major flooding—although it has been close a few times. Figure 2 shows runoff from the 2017 Snowmageddon year, and while flows on the Lower Boise River did exceed “bank full” flows of 6,500cfs and caused some minor flooding, the natural (undammed) combined flows of the N.F., M.F. and S.F. of the Boise rivers reached peaks of 15,000cfs – 24,000cfs which would have been a major flood event for Boise.

The Owyhee reservoir was sitting at 35% of capacity this winter (significantly below average) but has started to fill and is rising fast, as shown in Figure 3. Over the last 25 years the Lower Owyhee River has seen 7 years with high flows, but even though the Owyhee drainage had an excellent snowpack this year, Owyhee Reservoir had so little water carryover that it is unlikely that the lower Owyhee river will see high flows, which is too bad because that river could really benefit from higher flows to clean sediment left by side stream blowouts.

FREESTONE RIVERS AND SPRING CREEKS

Spring flows on freestone rivers like the M.F. Boise and the Wood River are 100% dictated by the snowpack and the weather. A quick warmup on a high snowpack year results in the highest flows, and with our high snowpack and cool spring there is likely to be some flooding when it finally warms up, so stay tuned to the BVFF Local Waters page and be careful. Spring Creeks can be a good place to escape high flows because they are not fed by runoff (make sure to check fishing regulations before you go to ensure it is open). Spring Creeks, such as Silver Creek, don’t see as significant range of flows, but high and low snowpack years do impact groundwater springs which changes flows some.

SPRING CLEANING

High spring flows are very healthy for a river: They clean out accumulated sediment which improves the river’s carrying capacity and keeps it connected to the floodplain. High flows clean and redistribute gravel for trout spawning, although rivers below a dam don’t get new gravel from upstream because it gets trapped behind the dam. Over time this limits the amount of wild trout spawning habitat, which is why we recently added gravel to the Boise River and are working to add gravel on the Owyhee. Luckily the S.F. of the Boise has some good tributaries that bring in gravel when they blow-out which periodically refreshes the spawning gravel on that river.

Removing accumulated sediment is good for insect life as well. For example, after high flows on the Owyhee, caddis and stonefly populations improve although some slow water insects like callibaetis mayflys get swept away and take a few years to recolonize. When planning your summer fishing trips keep in mind that high water years usually delay hatch timing because of the colder runoff, compared to low water years when rivers warm up sooner which accelerates hatches. For an example of how runoff impacts hatches see this month’s Bug Corner.

SIDE CHANNEL PROTECTION

As flows come up the Lower Boise River stays “in bank” until the river reaches 7,000cfs and the water gets very fast, compared to the Lower Owyhee River which comes out of bank quickly, spreads out and stays at a much lower velocity. High velocity flows are difficult for juvenile trout, especially brown trout fry that recently emerged from their redds/nests in March. Side channels provide refuge for trout to escape the hurtling velocities of the main river. Figure 4 shows the “BVFF Side Channel” on the Boise River at winter flows and at high runoff flows. While the main river is raging with little place for trout to hide, you can see numerous areas of softer water and good woody cover in the side channel where trout can hold. The location of our gravel augmentation is circled in the photo: We intentionally added it on an inside corner to protect it from higher flows and it will be interesting to see how much of it stays put and where Mother Nature decides she wants to relocate some of it. We will volunteer with IDF&G on their Fall Shoreline Fry Surveys again this Fall to evaluate the side channel gravel and see how the juvenile trout population fared.

The Owyhee River below Owyhee Reservoir in Oregon is one of the best brown trout streams in the West and a favorite place for anglers from the Treasure Valley to Fish. But as good as it is, the Owyhee River could even be better if it had more trout spawning habitat.

Boise Valley Fly Fishers (BVFF) has worked with the Oregon Department of Fish and Wildlife (ODFW) to monitor brown trout spawning since 2016. The brown trout population and number of redds varies year to year, but one common theme every year is that most of the brown trout spawning happens in the top 5 miles of river and very few fish spawn downstream by the Owyhee River Ranch even though the water quality and insect population in that reach is very good.

In Fall of 2021 we began an effort with ODFW to do a gravel augmentation to improve the spawning habitat on the lower reaches of the Owyhee River. We have determined that the run below the intermittent Sand Hollow creek has the right water depth and velocity for trout spawning but it lacks the smaller gravels needed. By adding gravel to this location trout will have a productive place to spawn which will improve the trout population in the lower reaches of the river.

BVFF’s gravel augmentations on the Boise River in Idaho have been very successful and we have high expectations for the potential improvement to the trout population on the Owyhee River. We have secured partial funding through grants from Fly Fishers International and ODFW, but the cost of doing a large gravel augmentation at a remote location is considerably higher than our small gravel augmentations on the Boise River. The costs are also higher for doing any stream alteration work in Oregon because of additional permitting.

We are raising money for the gravel augmentation through our internal club fundraiser “Greenbacks For Redds” and through the Idaho Gives Campaign which runs May 1st through May 4th, 2023. Please consider helping us reach our gravel augmentation goal by contributing to the Idaho Gives Campaign. Donations made through Idaho Gives will be generously matched up to $1,000 by St. Clair Contractors, who has been a great partner in helping with BVFF’s Boise River gravel augmentation and our Angler Access project at the new Diane Moore Nature Center.

OUR THANKS goes to the people who have already purchased Greenbacks to support our gravel augmentation effort on the Boise River. Funds left over from that project will be applied to the Owyhee River gravel augmentation.

THANK YOU!

George Butts, Troy Pearse, Brian Martin, Robert Boatright, Fairlee Frey, Greg Mondin, Dennis Moore,

Dennis Fomin, Gary Gettman, Larry Hill, Kathi Rothner, Scott Lenz, Kent Christensen, Tim Hall, Terry Burton,

Klaus Kissman, Jack Truschel, Johnny Rogers, Robert Hurley, Brad Stewart, Ray Arguello, Michael Stahl,

John Slovick, Jason Hansen, Tim Opp, Jim Kazakoff, Guy Beaudine, Ron Gambassi, James Murry, Joel Peterson, Ralph Stark, Joe Barberio, and Mike Schwiebert.

When river flows come up, side channels are a safe haven for trout to seek shelter from the heavy currents. Side channel protection is especially important for juvenile trout, including baby brown trout that recently emerged from their redds/nests and don’t swim very well yet.

Here is a photo of the side channel where BVFF has been working to improve trout habitat. You can see the main river is raging but there are numerous soft areas in the side channel for trout, including the corner where we added some woody cover. The gravel BVFF added to the side channel this Spring is tucked out of the main current and is at a good depth and flow for rainbows to spawn. We will keep an eye on it and report spawning activity.

Our weather is finally heating up and there is still lots of snow in the mountains to melt and runoff. Keeping on track of water conditions can help you avoid showing up at the river only to find it is blown-out, unsafe and unfishable. BVFF’s Local Waters webpage has links to current flows and water temperatures for nearby rivers as well as reservoir and boat ramp conditions and is a good tool to help you plan your fishing trip.

I also use the “riverflows.net” app on my Android phone to track river flows on my favorite rivers. I like that it includes both USGS stations and AHPS (Advanced Hydrologic Prediction Service) stations that give you insights into how the river is expected to rise or drop over the next week.

Here is a look at the main screen of my river “favorites”. For some stations you will notice both a USGS and AHPS entry. Here is a look at both of those water flow graphs. You can see that the USGS graph goes back further in time, but the AHPS graph includes a forecast for the next week.  As you can see in the MF Boise forecast, flows are headed up! So be safe out there.

Boise Valley Fly Fishers has wrapped up their Brown Trout Redd mapping on the Lower Boise River and delivered updated waterproof maps to Boise Flood District 10 for use in their annual winter river maintenance. Now that the redd map is complete we plan to refloat the river yearly to identify which sites are active and communicate that to the Boise Flood District and Idaho Fish and Game. Last year the Boise Flood District reported that the redd mapping had enabled them to avoid all but one of the redd areas and the Flood District excavator driver, shown in Figure 1 holding the Redd Map along with new Assistant District Manager Mark Zirschky, told me that he has also been able to identify and avoid smaller redd areas that were not on the map. Well done and thank you to the Boise Flood District!

BVFF is tracking 50 redd sites across 22 miles of the Boise River, from the Willow Lane boat ramp in Boise down to Star. This year we were able to add the South Chann el around Eagle Island, which had fewer redd sites than the North Channel, but some of the sites had quite large gravel deposits and many brown trout redds. Figure 2 shows the area of the Boise River that we are tracking, and you can see how many more redd sites are in the North Channel vs the South Channel. There are many factors that could be responsible, but one reason is the North Channel has more “sinuosity” (a measure of the number of curves in a river channel) resulting in more areas where smaller gravels settle out that trout can use to spawn.

This year spawning redds were observed as early as the first week of November and as late as the 2nd week of December. Spawning locations were consistent between 2021 and 2022 but this year we counted fewer total numbers of redds. This is partially due to being more conservative in our counting and not including some areas that IDF&G fish biologist Tim D’Amico thought could be caused by scour from higher velocity flows, but even then the overall redd numbers appear to be down. On a positive note, the number of redds in our BVFF Side Channel increased this year because of gravel shifting into prime locations and having a little more water flowing into the channel. Idaho Fish and Game is very interested in tracking the redd locations from year to year and we will continue to report our findings to them.

This year we piloted a process of noting the location of downed trees as we floated the river, to help the Boise flood district plan their winter maintenance work, which has opened the door for more discussions with the Flood District and Idaho Fish and Game on identifying trees that would be good to try and retain for trout fry protection. A great continuation of our partnership on the Boise River.

Last year we floated in November and missed some of the brown trout redds because browns were not done spawning so this year we waited until December to make sure that brown trout spawning activity was complete. Next year we will switch to checking known redd-zones for activity which should allow us some weekend outings in November. Thanks to our volunteers (George Chen, Klaus Kissman, George Butts, Johnny Rogers, and Troy Pearse) who braved cold days on the river to count redds.

In February, Boise Valley Fly Fishers added 15 cubic yards of gravel to a side channel on the Lower Boise River located by the New Dry Creek diversion below Glenwood Bridge. Thanks to our awesome volunteers (Ray Arguello, Tim Opp, Dwane May, Guy Beaudine, Jose' DeSousa, Mike Stahl, Klaus Kissman, George Butts , Scott Lenz , Russ Dodd, Johnny Rogers, Jeff Jones, Troy Pearse and Dennis Fomin) who stuck with the project thru several delays and complications.

Two years ago we added 15 cubic yards of gravel but spread it out in 3 locations on the side channel. That worked well as a way to seed the channel with spawning gravel and since then we have seen a significant increase in trout spawning. The gravel has slowly been working its way down the side channel and Mother Nature has been sorting and depositing it in productive locations for trout to use. This time we decided to add all of the gravel at the top both to refresh the gravel in a location that rainbows like to spawn and to give Mother Nature more building materials to move downstream.

In addition to adding spawning gravel we also worked with fish habitat restoration experts at BioAnalysts and Idaho Fish and Game to improve the woody cover on the side channel to give trout fry refuge after they hatch. Idaho Fish and Game tells us that having this woody cover is the key to helping trout fry survive into adulthood.

One issue we have had during the low water fall and winter is keeping good flows coming into the side channel because the public throws rocks and logs across the top in order to cross, which reduces inflows.Brown Trout

need sufficient flows to spawn in Fall and their nests/redds need those flows continued through the winter to oxygenate the eggs. This year the Boise Flood District placed some large boulders near the top of the side channel that can be used as steps to cross--let’s hope the public uses them.

A BIG Thank You to our project partners: To Sunroc for donating the gravel again and to Boise Flood District 10 for their assistance moving it into the side channel.

A special thanks to those people who bought Greenbacks to support our gravel augmentation projects (Robert Boatright, Dennis Moore, Larry Hill, Scott Lentz, Kent Christensen, Tim Hall, Terry Burton, Klaus Kissman, Jack Trushel, Johnny Rogers, Bob Hurley, Brad Stewart, Ray Arguello, Mike Stahl, John Slovick, Jason Hansen, Tim Opp, Guy Beaudine, Jim Kazakoff, George Butts, Brian Martin, Troy Pearse, Ron Gambassi, James Murry, Joel Peterson, Ralph Stark, and Joe Barberio). We are still working to raise money for the Owyhee Gravel Augmentation. If you are interested in helping please consider buying a $25 Greenback at the BVFF Store.

Newspaper Stories about the project can be found at:

Idaho Press

Capital Press

Idaho Statesman (March 15)

KTVB Channel 7 News