This graph shows the water levels in both Tyee and Swan lakes on August 5. The red line shows this year's water levels compared to previous years.
When the water level (brown line) in Tyee Lake reaches the green line, then SEAPA will begin selling power to Ketchikan from Tyee Lake. Once the water level falls below the red line, then SEAPA will stop selling power to Ketchikan.
As the dry weather persists though the summer, Tyee Lake water levels continue to be below the normal levels for early August.
As part of the Southeast Alaska Power Agency, Tyee Lake dedicates its power to Petersburg and Wrangell, while Swan Lake produces power for Ketchikan. Water in Tyee Lake reached 1,313 feet Monday morning. The water level is lower than the norm for Tyee Lake this time of year, but it is higher than the water level this time last year, said Utility Director Karl Hagerman.
“The good news is that we finally achieved a level higher than last year,” said Hagerman. “That’s a bit of a silver lining, but still not very good on the lake level.”
Hagerman said if this dry weather continues, then the water level in Tyee Lake will start to drop like last year. Snow in the area has all melted, so Tyee Lake is relying on precipitation to fill it. Hagerman said if a historically wet fall doesn’t occur, then there’s a chance that Petersburg and Wrangell will have to generate power through diesel generators at some point during the winter. He said he’s optimistic that Southeast Alaska will return to a somewhat normal state and that lakes will receive some much needed rain.
SEAPA has an operations draft limit for Tyee Lake set at 1,260 feet. Once the water level in Tyee Lake reaches SEAPA’s operations draft limit, then the hydroelectric project will no longer be able to draw water to produce power. There is a second draft limit set by the Federal Energy Regulatory Commission at 1,250 feet. If Tyee Lake has already reached the 1,260 feet limit, but there is a major power outage or a failure in the system, Petersburg and Wrangell will still have that extra 10 feet of water to produce power.
Tyee Lake also has a spill limit. If water in the lake reaches 1,400 feet, then water will start to spill over the lake into the creek; however, Hagerman said Tyee Lake is in no danger of overflowing.
“When a hydropower lake is overflowing, that’s a loss of energy,” said Hagerman. “We want to generate as much water as we can with that water and not let it go down the creek without generating power.”
In addition to receiving power from Tyee Lake, Petersburg has its own hydroelectric project at Blind Slough that draws water from Crystal Lake. Hagerman said that last year, the water level in Crystal Lake got down to the lowest it has ever been before. Crystal Lake is currently about four feet away from last year’s record water level. The bottom of the pipe that sucks in water is at about 1,267 feet. The Blind Slough Hydroelectric project operates between 1,274 feet and 1,294. If water levels reach 1,294, the water will spill out. As of Tuesday morning, Crystal Lake was at 1,283.52 feet.
Hagerman said that Crystal Lake had to provide more water to the Crystal Lake Hatchery recently since they are about to start harvesting king salmon eggs and sperm. The hydroelectric project is drawing water from Crystal Lake at about .15 feet per day. If the hydroelectric project kept up that pace, then it would take 26 days to get down to the lowest water level Crystal Lake has ever seen. If that happens, Hagerman said there is concern that water will begin to vortex above the headstock, and air could get sucked in, which would damage the equipment.
“It’s not the end of the game, but we’re just going to have to keep a close eye on the lake and make sure we don’t have the vortex,” said Hagerman.
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