Lake Management

September 4, 2024 | Fall 2024 Release Announcement and Summer Operations Update

Summer Operations
Construction of the Priest Lake Outlet Dam was complete as of Spring of 2024.  One modification at the dam included a six-inch gate height increase to all eleven gates. With the gate height increase, it is now physically possible to hold the lake level at 3.5 feet during the recreation season. The gate height modification was completed in Spring of 2022.

Idaho Legislators updated Idaho Code § 70-507 in 2018 to establish how the lake level will be maintained throughout the recreation season as follows, depending on the anticipated type of water year:

• In dry and marginally dry years, the lake level is to be held between 3.0 and 3.5 feet, and
• In wet to normal years, the lake level is to be held at 3.0 feet.

The dam modifications and corresponding statute revisions were developed to avoid a repeat of the summer of 2015, in which drought led to extreme conditions. That summer, to maintain the required minimum lake level of 3.0 feet, the flow to Priest River below the dam was reduced to 42 cfs. Stakeholders found such low flow in the Priest River to be unacceptable. To prevent similar low flow in the Priest River in dry years, a higher lake level is maintained during the recreational season. In other words, keeping lake levels higher earlier in summer facilitates preservation of higher flow in the Priest River throughout the summer.

As you may be aware, weather and environmental conditions vary significantly from year to year at Priest Lake, and lake operations must accommodate the variation. Considering weather and environmental variations, along with the newer gate height modifications, the Department continues to develop best practices for managing lake levels. The Department invites feedback to help inform future operations, planning, and development of best practices for managing the additional lake level during dry to marginally dry water years. Helpful information would include photos with dates. Please email your feedback to northerninfo@idwr.idaho.gov.

Fall 2024 Release

The Fall release of Priest Lake will begin on October 1, 2024. On that date, the lake will be lowered below 3.0 feet.  Please plan accordingly.

Please direct any questions or comments to northerninfo@idwr.idaho.gov or call (208) 762-2800.

April 23, 2024:

May is fast-approaching, and operations are underway to bring the lake level up to the summer recreation level.

As of today, the lake level is at 1.6 feet. IDWR staff members continue to watch two SNOTEL sites, Bunchgrass Meadow and Hidden Lake, both at an elevation of about 5000 feet. Much of the snow at lower elevations has already melted, and staff will monitor the Snotel sites to react to any sudden influxes of high-elevation runoff into the lake.

Here are links to the two SNOTEL sites:
Bunchgrass Meadow: AWS Plot (usda.gov)
Hidden Lake: AWS Plot (usda.gov)

Hydrologists are predicting a warmer-than-average and dryer-than-average summer. Accordingly, the Department will aim to stabilize the lake level to 3.4 feet in the early portion of the recreation season.

For questions contact Michelle Richman, IDWR Northern Regional Manager, northerninfo@idwr.idaho.gov or (208) 762-2800.

February 16, 2024 | End-of-Construction Update:

Construction at the dam by Northbank Civil and Marine is wrapping up with some final tasks, such as rock placement and gate seal work. Northbank has begun the process of demobilizing. Normal gate operation is expected to resume by early next week. As you are likely aware, the construction limited the flow through the dam to a maximum of 800 cfs over the winter months. At the same time, rain-on-snow and warmer temperatures led to significant inflow into the lake. This combination of circumstances caused lake levels to increase through the winter months. The current lake level is 2.53 feet.

The plan for the next few weeks is to bring the lake level down to approximately 1.5 feet and to hold that level while monitoring the Snotel sites (see links below). Both sites are near 65% of normal snow water equivalent. Drought conditions are predicted to continue in Northern Idaho through September. Subsequent gate operations and lake level management will depend on the speed at which the runoff comes out of the Priest River basin.

Snotel sites:
Bunchgrass Meadow: AWS Plot (usda.gov)
Hidden Lake: AWS Plot (usda.gov)

As for prior years, the goal will be to have the lake level to at least 3.0 feet by Memorial Day.

For questions contact Michelle Richman, IDWR Northern Regional Manager, northerninfo@idwr.idaho.gov or (208) 762-2800.

December 2023 Construction Update:

Construction at the dam continues in full swing by Northbank Civil and Marine. In this construction phase, 100% of the flow through the dam is being directed through a constructed flume within the dam. This creates a dewatered area on the south side of the dam that allows for construction to occur. It appears that the project is on schedule to pour concrete at the south side of the dam prior to mid-December. The construction crew will pause for the holidays and then resume after the new year. In the meantime, IDWR will continue to pass all water through the dam via the constructed flume until construction on the south side is complete. The flume capacity is nearly 800 cfs. Precipitation, including rain on snow, has led to — and will likely continue to lead to — greater inflow to the lake, which leads to increases in the lake level.

The purpose of this update is to provide information about these atypical operations and to reiterate that these are temporary measures due to specific construction activities. The Department will continue to provide periodic updates during the project.

For questions contact Michelle Richman, IDWR Northern Regional Manager, northerninfo@idwr.idaho.gov or (208) 762-2800.

November 2023 | Construction Update:

As many of you are aware, mobilization and construction on the Priest Lake Outlet Dam resumed on October 16, 2023. Idaho Department of Water Resources is working with the construction company, Northbank Civil and Marine, to facilitate successful completion of the project. You may have recently noticed that the lake reached the .1-foot mark on November 1, 2023. For the two weeks following November 1, the Department will work with Northbank as they construct a cofferdam. (This effort directs 100% of the flow through a constructed flume to allow for construction of the concrete pad on the south side of the river.) The Department is, therefore, operating gates to reduce flow to about 100 cfs during the day to enable construction activities to proceed. During non-construction hours, the Department will operate gates to increase flow through the dam to 400 cfs or more. Due to the rain and day-time gate closures, the lake is rising, and it is currently at .25 feet.

The purpose of this update is to provide information about these atypical operations and to inform you that these are temporary measures due to specific construction activities. The Department anticipates typical winter operations to resume by mid-November. The Department will provide periodic updates during the project.

Fall 2023:

On October 1, 2023, IDWR will begin releasing the lake level at Priest Lake below 3.0 feet. This will allow construction to resume at the Priest Lake Outlet Dam this Fall/Winter. The primary construction efforts will take place on the south side of the dam and include extension of the downstream concrete pad and the addition of boulders downstream of the dam for added scour protection.

Drawdown gate operations will lead to flow increases in the Priest River that will range between 100 and 400 cubic feet per second (cfs) at a time. To enable the construction crew to begin work as soon as possible, three operations will occur daily between October 1 and October 5. Those three operations each day will cumulatively result in daily increases of less than 1000 cfs for the day. The lake level will likely drop to 2.0 feet prior to October 8. The lake level will continue through the remainder of October to decline to the winter lake level.

Please stay clear of the dam to avoid fast-moving water both upstream and downstream of the dam for your safety.

For questions contact Michelle Richman, IDWR Northern Regional Manager, northerninfo@idwr.idaho.gov or (208) 762-2800.

May 15, 2023:

May’s warm temperatures melted much of the snow in the Priest Lake basin. Priest Lake levels peaked once last week and could peak again as snow continues to melt.

As of today, the lake level is 4.21 feet (ft), with and flow through the dam is 5360 cubic feet per second (cfs). Department staff continue to watch two SNOTEL sites, Bunchgrass Meadow and Hidden Lake, both at an elevation of about 5000 ft. The general rule of thumb is peak flow into Priest Lake occurs when the Hidden Lake site has about 75% melt-out and when the Bunchgrass Meadow site has about 60% melt-out. These melt-out conditions (75% and 60%) are approaching with the warmer temperatures. Below are links to the SNOTEL charts for both the Bunchgrass Meadow and Hidden Lake sites.

Bunchgrass Meadow:  AWS Plot (usda.gov)
Hidden Lake:  AWS Plot (usda.gov)

Once peak inflow and a corresponding peak lake level occur, the gates will be operated to maintain the lake level for summer recreation. The Department’s hydrologists are predicting a dry year, and the Department will aim to stabilize the lake level at 3.2 to 3.3 ft through the summer months.

For questions contact Michelle Richman, IDWR Northern Regional Manager, northerninfo@idwr.idaho.gov or (208) 762-2800.

April 2023:

As of early April, rain and warmer temperatures have led to rising water levels in Priest Lake. IDWR staff are watching two SNOTEL sites, Bunchgrass Meadow and Hidden Lake. Both sites are at an elevation of about 5000 feet and may receive more snow this season before a reduction in snow occurs. It is difficult to know when peak flow will occur each year. The general rule of thumb is that peak flow into Priest Lake occurs when the Hidden Lake site has about 75% melt-out and when the Bunchgrass Meadow site has about 60% melt-out. Below are the links to the SNOTEL charts for both sites.

Bunchgrass Meadow:  AWS Plot (usda.gov)
Hidden Lake:  AWS Plot (usda.gov)

Snow is presently melting at lower elevations in the Priest Lake Basin. As snow continues to melt and the Priest Lake water level steadily rises, the outlet dam gates will be managed to pass some runoff through the dam. The Department’s goal is to have the lake level at 3 feet by Memorial Day Weekend. Keep in mind that peak lake level and timing of the peak lake level is determined by Mother Nature.

The Department’s hydrologists are seeing preliminary predictions for a dry year; however, that could change if the Priest River Basin continues to receive precipitation. If this is a dry year, the Department will likely aim to hold the lake around 3.2 feet once the lake level is stabilized.

For questions contact Michelle Richman, IDWR Northern Regional Manager, northerninfo@idwr.idaho.gov or (208) 762-2800.

September 2022:

IDWR will begin drawing down Priest Lake on October 10th this year.  Flows through the Outlet Dam will increase daily to achieve the winter lake level by November 1.  This will facilitate kokanee spawning and accommodate boat and dock winterizing needs along the shoreline.  Construction and hydrologic conditions vary annually, which guide the operation decisions.  This winter, construction work on the dam will not take place other than on-site surveying.  Construction is anticipated to resume next October of 2023.

For questions contact Michelle Richman, IDWR Northern Regional Manager, northerninfo@idwr.idaho.gov or (208) 762-2800.