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Lucky Peak is being drawn down 125 feet to do repairs on the Turner Gulch boat ramp. The low water levels in Lucky Peak will impact water temperatures on the Boise river this August. Water temperatures on the whole river are expected to rise and stay above 66 degrees for several weeks, which is very hard on trout.

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The US Army Corps has started down Lucky Peak in order to do a repair on the Turner Gulch boat ramp, which means by the end of August, there will be no ramps available.  The Lucky Peak Dam and Lake – WallaWallaUSACE Facebook Page recently posted this warning:

BOATERS - Remember to be very cautious about any long term mooring, beaching, or anchoring as the continued fall of the lake is about 2’ per day. No salvage services are available and if your boat becomes stranded it will likely remain until the spring fill so be careful.

The figure below shows the current elevation of the reservoir (as of 7/27/24) and the different boat ramps. You can find the latest version of this graph under the "Boat Ramps" section of BVFF's Local Waters web page.

BOISE RIVER FLOWS

Flows on the main Boise through town are not expected to rise during the drawdown. The drawdown is being achieved by reducing inflows from Arrowrock and Anderson Ranch Reservoirs (Arrowrock cut inflows first and Anderson will reduce flows the 3rd week of August). This approach allows them to maintain the water in upstream reservoirs for future irrigation needs.

LUCKY PEAK OUTFLOW ZONE

Tailwaters like Lucky Peak and Anderson Ranch Dam usually release cold water all summer long because the water is coming out of the bottom below the thermocline where water is colder. However, the Lucky Peak drawdown will bring the warmer surface epilimnion layer of water into the outlet zone which will increase the temperature of outflows.

2024 EARLY AND DEEP DRAWDOWN

Lucky Peak is typically drawn-down around 20 feet in August as a way to manage water for the next irrigation season. In 2021, because of prolonged drought conditions, the drawdown was started a couple weeks earlier than normal and by the end of August Lucky Peak was 75 feet lower than usual. This drawdown resulted in the warmer surface water entering the outlet-zone which resulted in water temps being released from Lucky Peak that were 67 degrees all day long with water temperatures downstream at Glenwood Bridge reaching the low 70s. (Water temperature data was obtained from a public records request from the City of Boise who has a temperature logger just below Lucky Peak dam. Click on the graph to see a larger version.)

Looking back at Lucky Peak Reservoir elevation data, there has never been a drawdown in August like this. This year’s draw down is likely to impact Boise River water temperatures even more than 2021, because the reservoir level will drop another 33 feet than it did in 2021 (down 108 feet from 2020!), which will increase the percentage of outflows that are the warmer surface layer. There is no way to know how warm Lucky Peak’s outflow water temperatures will get, but it is possible they will reach the lower 70s, which means water temperatures at Glenwood bridge would warm into the mid 70s. 

High water temperatures are hard on trout, especially when the temperatures don’t drop below 65 degrees overnight for trout the bleed off the excess heat their bodies gained. Sadly, once Lucky Peak starts putting out water temperatures over 66 degrees in mid-August, this condition will exist on the entire river. Trout will seek out cool water refuge zones near ground springs and deeper holes, but will become overwhelmed by the prolonged high water temperatures.

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