This report considers impacts on the Nez Perce Tribe, the Yakama Indian Nation, the Confederated Tribes of the Umatilla Indian Reservation and the Confederated Tribes of the Warms Springs Reservation of Oregon. Each of these tribes is a sovereign nation, and is unique in many ways. At the same time, these four tribes have retained close linkages over the years: through blood ties; in cooperative pursuit of salmon and other food; and through religion, sharing of languages and similarity of treaties.

The Report also assesses impacts on the Shoshone-Bannock peoples, who live further upriver in the Snake River drainage, and who are more separated from the other four study tribes.