The damming "linked the rivers and lakes of Ootsa, Intata, Whitesail, Chelaslie, Tetachuck, Tahtsa and Natalkuz into the reservoir with a surface area of over 90,000 hectares." "The water of these lakes and rivers was diverted westward to the Pacific Ocean, instead of eastward to the Fraser River."
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.
In the late 1940s, University of British Columbia professor Charles Edward Borden shifted his attention toward urgent salvage archaeology in in the Nechako Canyon after learning that ALCAN planned on flooding the Nechako Canyon to supply power for their smelter in Kitimat (known as Kemano I Project). In 1951 Borden and his protégé, anthropology student, Wilson Duff located over 130 sites of importance to Cheslatta T'en history. They conducted more intensive investigations prior to the flooding of the area. The damming triggered "devastating changes for First Nations communities whose traditional territories lay in their path, including the destruction of Aboriginal gravesites, territories, livelihoods, and archaeological sites." In 1957, Alcan opened the gate of the spillway to Skin's Lake desecrating Cheslatta graves, which came to public attention during the Royal Commission on Aboriginal Peoples.