The creation of the reservoir flooded the series of lakes which typified the upper Nechako basin and in the process rendered the Quanchus Range, which lies between the north and south arms of the reservoir, a virtual island. The names of lakes amalgamated into the reservoir are perpetuated as names for the various stretches of water. The north arm includes Ootsa Lake, Whitesail Lake, and Whitesail Reach, the south arm Eutsuk Lake, Natalkuz Lake, Chedakuz Arm, Knewstubb Lake, Tetachuck Lake and others. Because Ootsa Lake is the largest of the original lakes its name is sometimes used for the whole reservoir, though the official name remains Nechako Reservoir.