 The resulting dam would have created a lake roughly the size of Lake Erie , making it the largest man @-@ made reservoir in the world . The plan for the dam itself called for a concrete structure 530 feet ( 162 m ) high with a top length of about 4 @,@ 700 feet ( 1 @,@ 430 m ) . The proposed power facilities would have consistently generated between 3 @.@ 5 and 5 gigawatts of electricity , based on the flow of the river as it differs between winter and summer . 
