La Grande River is a river in northwestern Quebec, Canada, which rises in the highlands of north central Quebec and flows roughly 900 km west to drain into James Bay. It is the second largest river in Quebec, surpassed only by the Saint Lawrence River.
Originally, the La Grande River drained an area of 97,400 km2 and had a mean discharge of 1,690 m3/s. Since the 1980s when hydroelectric development diverted the Eastmain and Caniapiscau rivers into the La Grande, its total catchment area has increased to about 175,000 km2, and its mean discharge increased to more than 3,400 m3/s. In November 2009, the Rupert River was also partially diverted, adding another 31,430 km2 to the basin.
Wikipedia https://en.wikipedia.org/wiki/La_Grande_River
Coordinates 53°44'52.908" N -78°10'31.63" E