Rio Tinto has their water temperature management target period set for a month, beginning July 20.
The water level in the Nechako River will increase by approximately 0.9 m – 1.6 m when the Summer Temperature Management Program (STMP) begins.
During the STMP, flow in the Nechako River at Cheslatta Falls is maintained between 170 cubic metres per second and 283 cubic metres per second, said Justus Benckhuysen, Nechako Operations Coordinator for Rio Tinto.
“Because it takes several days for water to travel that distance, spillway discharge to achieve the temperature target start on July 15 – 16,” he said.
The temperature target location is the Nechako River immediately upstream of the confluence with the Stuart River (Finmore), Benckhuysen said.
“Because the Cheslatta watershed lakes causes a delay in spillway discharge reaching the target location at Finmore, the lakes are pre-filled starting July 11,” he added.
The lakes are pre-filled to a level that achieves a minimum lake outflow of 170 cubic metres per second and is measured at the Water Survey of Canada Station which is located downstream of the Cheslatta Falls, Benckhuysen explained.
He said that during the STMP period starting July 20 and ending August 20, the spillway discharge will be an absolute minimum of 14.2 cubic metres per second and a maximum of 453.1 cubic metres per second.
“The water level in different locations in the Nechako River will depend on additional inputs from tributaries such as Nautley River,” Benckhuysen said.