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The Priest Lake SIPHON


The Idaho Department of Fish and Game is proposing to spend between $8.2 - $16.5 million to build a siphon that will tap the colder deep water (hypolimnion) of Priest Lake.  The siphon, a 5-foot diameter, 7,500 - 8,000-foot pipe, would run from the headwaters of Priest River, through Match Bay, the full length of the Outlet channel and into Coolin Bay/Priest Lake, out to a depth of at least sixty feet.  The siphon would bypass 75% of the natural, existing water volume and current flow rates away from this popular and highly used area and pipe it directly into Priest River.  They have stated their goal is to use the "colder water” to lower the temperature of the 45 mile-long Priest River, to encourage improved natural fish production, creating a “high-value fishery” one that will generate $1.5 million in annual economic benefits to the local area.  

We, the stakeholders of Priest Lake, formally go on record as opposing THE PRIEST LAKE SIPHON. 
Our opposition is based on many factors, several of which are outlined below.


We do not consent to the diversion of the deep cold waters of Priest Lake for the purpose of providing colder water, multiple miles downstream, in an attempt to artificially build a “high-value fishery” where none previously existed.  Priest River, has historically (even prior to the dam), been “warm water impaired” and very dependent on Priest Lake’s surface water, being warmer in the summer months as it always has been.  

We object to the artificial manipulation of an ecosystem based upon an unproven theoretical computer model in violation of our senior water rights.  The only way this theory can be “proven” is to build it!  If it fails to achieve modeled results, fails to yield a sustainable fishery, or produces other environmental damage, it is only the stakeholders of Priest Lake that will have to live with the resultant consequences.

IDFG has failed to recognize that a water right would need to be obtained for the proposed siphon which is not a foregone conclusion.  This lengthy, complicated process would require filing an application with the Idaho Department of Water Resources, an opportunity for protests to be filed, and a trial-like contested administrative proceeding, subject to court appeals.  Among other things, IDFG would need to prove that the proposed diversion of water from Priest Lake is in the local public interest and that it won’t injure the existing 1927-priority water right held for the lake by the Governor of the State of Idaho.   



We oppose the use of public monies for a project that is ill-conceived with its justification based on unrealistic economics and outcomes.   These funds and department resources could be better utilized, if they were dedicated to priorities and projects that would better benefit the citizens, taxpayers, property owners, and visitors to the great State of Idaho.

IDFG has stated that by developing a “high value fishery” would generate $1.5 million in annual benefits to the local area. To achieve this level of benefit, based on IDFG’s own data, would require an additional 7,300 fisher-people visits to Priest River every year - a number not even in the realm of the possible, due to many reasons, including the short season and lack of the public river accessibility. IDFG have also stated they will not stock the river. A senior IDFG official said “in any event, we have no intention of trying to support the fishery with stocking if a cold-water bypass is implemented.  Rather we would rely on reproduction of wild fish, that's free”

Since when is $8-$16 million in construction costs make free fish? where is the proof that by adding colder water to Priest River will ever enable a naturally developed “high-value fishery” when it could not even be done through restocking?   IDFG has stated that it would take around 10 years to develop a “high-value fishery.”  There is no data that IDFG has provided to validate this estimate and again, during this period, there is no way that the annual benefits economics, would be achievable, if ever!

The siphon’s economic life is projected to be 20 years, to ensure that any “pipe” can be replaced, assuming 2% annual inflation, the cumulative cost through 2040, would be around double, requiring IDFG to set aside somewhere between $180,000-$450,000 each year for the next 20 years, to ensure funds are available to fund the replacement. This is another expense that is not addressed in the costs of this project.  



There has been no comprehensive effort or studies by IDFG to explore more natural methods to address how Priest River and its tributaries could be cooled in support an improved fishery. There are many studies available that spell out the positive results to fisheries resulting from placement of a variety of rock weirs, islands, log deflectors, trees, etc. in and along the river to create cooler habitats for fish. Adopting a similar approach for Priest River and its tributaries would be a very natural and environmentally friendly, as well as a more economical way to help work toward IDFG goals rather than trying to create an artificial system that has significant downsides and highly questionable benefits. 

A 2021 article the Idaho State Fishery Manager, pointed out that quote…”trout are resilient and even extreme weather rarely has a long-term impact on populations -wild animals, for the most part are well equipped to survive fluctuations in environmental conditions, and trout, Idaho’s favorite fish, are no different.”

Another alternative to the siphon, that would cool the waters of Priest River, as put forward in the engineering study by McMillen Jacobs Associates, is the “Groundwater System.” This alternative takes ground water, from a locally-distributed cluster of groundwater wells located below the dam, and would pump cold water through a pump house system and back into the upper reaches of Priest River helping to cool the river. The construction costs for this system (2019 dollars) would be in the range of $684,000 - $1.7 million with summer annual operations and maintenance costs of around $157,000. This alternative is “significantly” less expensive than the siphon alternative, and “does not directly impact the lake or the Outlet Bay/channel”.

This alternative needs to be seriously considered and assessed by IDFG before any additional work is considered on the siphon!


We oppose the granting of any littoral permits from the Idaho Department of Lands (IDL) or US Army Corps of Engineers that will allow the destruction of approx. 1.5 miles of lake and Outlet channel bed, as a significant portion the 5 ft. diameter siphon pipe will be buried to a depth of around 7 feet, requiring  excavation that will destroy the existing Kokanee and other fish species spawning beds, as will as posing a significant risk to other aquatic species due to the debris caused by the operation.

No quality geologic or seismic studies have been done to determine the under lying composition of the geologic structure along the route of the siphon pipe. If bedrock or other significant findings exist, requiring blasting, significant dredging, or other major construction considerations, this must be accurately determined, along with the costs, permits, etc. as well as being communicated to us, the stakeholders, before any decision can be made to even consider proceeding with the pipe. A portion of the pipe, out in the lake, would not be buried but raised off the lake floor by concrete pedestals about every twenty feet apart. This would potentially create not only problems for fishing but, if visible, would spoil one of the great aesthetic values of Priest Lake... the deep clarity of water.  A visible pipe, at any depth is unacceptable!



No studies or assessments have been made to determine the toxicity of the sediment either in the Outlet Bay/channel or at the intake end of the siphon. Excavating a mile long, or longer, 7-foot-deep channel will disrupt sediments and the resultant suspension of that material is a given.  If the lake bed has any toxins present, either from past mining, logging or other sources, there is the potential this will be drawn into the siphon and passed downstream into Priest River. The lake has a mining and logging history and there is every possibility that disturbing any sediments, etc. could create issues. 



We believe a one-off study, to assess the potential ultimate impact resulting from decades of mining of the hypolimnion, will not be able to come close to assessing any unintended consequences nor the long-term impact the siphon will have on Priest Lake. 

The limnology study, commissioned by IDFG, measured one summer (2020) and assumed stasis. Problems that have occurred in several North American lakes, with cold water by-pass systems, have appeared over time.  Multi-year droughts, heat domes, the continuing impact of climatic changes, global warming, along with the impacts of fires and large-scale logging coupled with increased hypolimnion withdrawals and the impact of reduced winter recharge, all generate negative impacts on this resource over time. These factors can and have, in other lakes and reservoirs, resulting in the warming of the hypolimnion as well as creating other devastating impacts to their overall thermostructure and on their fishery.

“Cold water delivery schemes based on pre-bypass conditions will be overly optimistic.  One of the riskiest operating strategies is to have an overly optimistic projection for late summer cold water supplies and to ultimately run out of cold water before the temperature-sensitive life history stages (of the thermostructure) have been completed…..running out of cold water can result in a sudden increase in downstream temperatures.”  -Water Resources Research, Vol. 40W05204

This, at a minimum means, fish kill downstream and higher fish mortality should an adverse event occur.

"... managing impoundments is often a balancing act between seemingly disparate goals of achieving optimum condition above or below a dam, with undesirable consequences often occurring if the focus is disproportionately on a single goal.”   -Lake and Reservoir Management 22(3): 223-232,2006.

The siphon project is disproportionately focused on the single goal of transporting cold hypolimnion water downstream, for miles, to achieve a targeted temperature, it does not account for the thousands of variables, many of them negative, and feedback loops that may be affected. There are significant potential longer-term negative environmental consequences if the project is implemented.  The only real way to ascertain if these unintended consequences would occur is to build the siphon and find out. 

We, the stakeholders of Priest Lake, are the ones that will be directly impacted by the implementation of this decision. We refuse to accept this risk!



To date, the studies, papers, and models that have gone into determining the feasibility of the siphon are based on historic temperature and climate data and conditions. In some studies, the data used to justify the benefits of this, and other projects have been one point in time studies and are also not current. Regardless, none of the studies have been proofed or modeled for predicted changes in our climate. Global surface temperatures are predicted to continue to rise and this with other environmental changes will likely result in extreme climate fluctuations, drought, increases in water temperatures, and other biotic changes. A warmer climate will affect everything this project is attempting to achieve, and failure to take this factor into account, considering even some of the predicted impacts to the lake, regarding these studies, is both short-sighted and unacceptable. 



A growing challenge in lake management is the incidence of toxic algae bloom. This problem is occurring all over the nation and was devastating in N. Idaho in 2021, as high summer temperatures broke historic records. Hayden Lake, Spirit Lake, Lake Pend Oreille, and Priest Lake all had public advisories issued.  This was a first for Priest Lake, and it occurred in the exact area that would be impacted by the siphon which will reduce the water volume and flow rates by 75%. Historically, warm surface water continually flows out the dam. We believe that the water in the Outlet Bay/channel (being the only outlet for the entire Priest Lake drainage) will become more stagnant, become warmer, and further exacerbate the incidence of HAB. 

Factors contributing to HAB are complex, but warm, slow moving, stagnant water contributes to its development. HAB can cause poisoning and death to animals and humans as well. It also renders water undrinkable as it cannot be filtered and many homes at the lake still take some or all their water directly from the lake. Any incident of toxic algae blooms virtually shuts down all water recreation as well.

These concerns have previously been sent to IDEQ, Manager of Water Quality, Mr. Herron. He replied “I do see your concerns and have similar concerns. It makes me realize that the residents of Priest Lake do care about water quality and are informed about some of the planning that is being queued up.”   He said, “I think that notion could serve as an indication of the concern for the human dimension impacts of these various flow regime manipulations by the out of state interest partnership formed by this Cold-Water Bypass project and the citizens of Idaho, the impact to the economy, the misuse of the Endangered Species Act, the utilization of BPA money to effect these changes, and lack of coordination with the public that could be most impacted.”



There are invasive species currently present downstream that may very well benefit from lowering the temperature of Priest River, should the siphon succeed in delivering cooler water. They are present now, and in a historically “warm water impaired” river there is the danger that their population may well explode given a cooler environment. 



Considering the potential destruction of the Kokanee, and other species spawning beds in the channel, there has been no considered discussion regarding the siphon’s impact on the fishery above the dam. Any change in the lake’s temperature patterns or flow characteristics will certainly have a potential impact on the fishery and other aquatic organisms.  The intake section of the pipe, even with various screening techniques, will still suck up foreign material, as well as potentially kill fish and other aquatic life.  Changes any the fishery will potentially also have an adverse impact on the fishing population and economics of the lake. 

Maintenance, repairs, and cleaning of the siphon will also present major timing and seasonal challenges to keep from interfering with the public’s recreational use. The siphon’s discharge location, below the dam, will also create potential issues relative to erosion and destruction of the bank and existing riverbed.  The recreational impact of the siphon’s discharge location is a concern as there are many rafters and others using this section of the river, more so now since major work was done on Hwy. 57 to enlarge parking and access capability to the river. 

The dam, which is currently being rebuilt, has made no accommodation, either in design or budgets for The siphon.
How the siphon would be integrated into or around the dam is not known, nor is how the flows through the siphon would be managed and controlled.  The impact on the fishery above and below the dam is also unknown and could be very detrimental to fish populations and survival rates. 



It has been stated that the siphon would be implemented within a very “brief” construction period.  The true construction period, and its impact, is not known due to the lack of geologic and other seasonal information on the Outlet Bay/channel.  There are over one hundred boats that are in the Outlet area marinas, and they all require access to this area at varying times of the year, particularly during the summer and fall months.  Any reduction in access to this area will not only have a significant impact on the area’s economy but depending on the type of excavation needed, e.g., blasting, heavy dredging machinery access, noise, etc. many “permanent residents” residing along the construction area will be adversely impacted. 

Longer construction times may also be encountered due to disruptions in the supply chain for materials, and labor shortages, let alone cost increases due to inflation. Priest Lake could find itself with a semi-finished project that could cause years of disruption to both the citizens and recreational users and the economy of the Outlet and the lake. It is conceivable that if such disruptions continued, the project could be abandoned out of necessity, partially completed in perpetuity.



Dihydrogen Sulfide can be a component of the hypolimnion. Many Priestlakers have experienced those rare occasions when the lake “turns over” and produces a foul smell generated when the deep waters from the lake, containing Dihydrogen Sulfide surface.  

The siphon will lift those waters over the dam for the duration of the recreation season.  Should this occur, year-round residents and visitors may well experience this during the peak season of the year.   This condition would be unacceptable and could have unacceptable economic consequences. 



We the stakeholders of Priest Lake object to the siphon because we are not convinced that by piping cold water out of the lake, diverting it away from the environmentally sensitive Coolin Bay/channel, will result in improving Priest River’s 40 plus miles of temperature sufficient enough to build what IDFG has labeled a “high-value fishery.”   This is particularly true when considering the ongoing impacts of climate change to the lake and river.  

We are also not convinced that the economic benefits being promoted by IDFG will be able to be generated by spending millions of dollars in public money.  We are also not convinced that a project of this size, one with such potential environmental and public impact, will not cause significant negative unintended consequences over the short, medium and long term consequences, where remedies are few, if at all, and ones that will have destroyed one of the most beautiful lakes in all of North America in the process.  The Crown Jewel of Idaho - Priest Lake.


We must protect our children’s legacy at all costs. 



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