West Branch levels to drop Annual drawdown aids trout spawning

MILLINOCKET – Later this week, boaters and camp owners on the five lakes behind the North Twin Dam will see water levels begin to drop.

Although water levels at North Twin recovered from last year’s drought, they will begin dropping again as Great Lakes Hydro America (formerly Great Northern Energy) begins its annual drawdown for the lake trout spawning season.

“Our Federal Energy Regulatory Commission license requires that North Twin be drawn down to its lowest level of the year by Oct. 15 to allow lake trout to spawn in the impoundment,” said Dave Preble, Great Lakes Hydro superintendent.

Preble said late August is typically the time of year when the company begins drawing down water levels of the five lakes – North Twin, South Twin, Pemadumcook, Ambajejus and Elbow – behind the North Twin impoundment.

“We try to have North Twin down between 10 and 15 feet for when lake trout start spawning on Oct. 15,” he said. Preble said lake levels will drop by 1 to 1.5 feet a week during the next seven-week period, something the company does routinely every year to meet the requirements of its federal hydro license.

Preble said lake trout primarily spawn in Pemadumcook Lake. “They spawn on wind-swept rocky shores of the lakes,” he said. The hydro official said the company will hold the lower water level through Nov. 6 while lake trout spawn. Then, the company will bring the lake levels up several feet and retain those levels for the remainder of the year so the eggs are always covered by water.

The water levels in the five connecting lakes that make up the water storage system behind North Twin Dam currently are about 2.7 feet from full, and are up about 22 feet compared with this spring when they were nearly empty. Water levels behind Ripogenus Dam, the company’s largest storage area where water from dozens of lakes and ponds is stored, are about 8.4 feet from full.

The company’s 56.1 billion-cubic-foot water-storage system on the West Branch of the Penobscot River is about 71 percent full, or about 12 percent below the system average for this time of the year.

On Sept. 16, the company will begin reducing flows from McKay Station during weekdays, Preble said. Recreational weekend flows of at least 2,300 cubic feet per second will continue through Oct. 1. Water flows from McKay Station have been averaging about 2,800 cfs through the summer months.

Preble said precipitation so far this month had brought about one-half inch of rain in Millinocket, down 86 percent compared with the long-term average of 3.8 inches of rain. Pittston Farm, located farther north in the West Branch storage, received less than one-quarter inch of rain so far this month, or 95 percent less than the long-term average of 4.35 inches.

“We have a good summer in terms of recreational use,” said Preble. “After we got through June, everyone had what they needed recreationally and commercially on both the West Branch and the North Twin impoundment.”

Preble said the company typically makes any needed dam repairs during the annual drawdown period. Last week, the company began a $1.5 million project to upgrade various structural components of the North Twin Dam radial arm gates. The steel gates each are about 50 feet wide and 27 feet high. The upgrade project is expected to run about 20 weeks.

“We want to get information out to people so they will know the lake levels will start dropping and about the gate upgrade so people understand why they are seeing heavy equipment around North Twin dam,” he said.