s ▁Canadian ▁reach , ▁the ▁US ▁portion ▁of ▁the ▁river ▁had ▁already ▁been ▁heavily ▁developed ▁by ▁the ▁time ▁the ▁treat y ▁entered ▁into ▁force . ▁Because ▁the ▁US ▁role ▁in ▁the ▁agreement ▁was ▁largely ▁to ▁supply ▁power ▁generating ▁capacity , ▁and ▁that ▁capacity ▁was ▁already ▁in ▁place , ▁it ▁was ▁not ▁oblig ated ▁to ▁construct ▁any ▁new ▁d ams . ▁While ▁in ▁the ▁Upper ▁Columbia , ▁treat y ▁d ams ▁meant ▁the ▁filling ▁of ▁large ▁res er voir s , ▁sub mer ging ▁large ▁tract s ▁of ▁land , ▁on ▁the ▁Lower ▁Columbia ▁no ▁new ▁d ams ▁had ▁to ▁be ▁built . ▁The ▁local ▁effects ▁of ▁dam ▁construction ▁were ▁limited ▁to ▁those ▁of ▁the ▁Lib by ▁Dam ▁in ▁Mont ana . ▁The ▁US ▁was ▁author ized ▁to ▁build ▁this ▁optional ▁dam ▁on ▁the ▁K oot en ay ▁River , ▁a ▁trib ut ary ▁of ▁the ▁Columbia . ▁Lake ▁Ko oc an usa , ▁Lib by ▁Dam ' s ▁res er voir , ▁extends ▁some ▁distance ▁into ▁Canada . ▁ ▁Because ▁this ▁project ▁involved ▁a ▁trans bound ary ▁res er voir , ▁it ▁was ▁slow ▁to ▁move ▁from ▁planning ▁to ▁construction . ▁By ▁ 1 9 6 6 , ▁when ▁construction ▁began , ▁the ▁environmental ▁movement ▁had ▁begun ▁to ▁have ▁some ▁political ▁currency . ▁Environment al ▁impact ▁assess ments ▁found ▁that ▁this ▁dam ▁would ▁be ▁de le ter ious ▁to ▁a ▁variety ▁of ▁large ▁game ▁animals , ▁including ▁big - horn ed ▁sheep ▁and ▁el k . ▁While ▁the ▁Lib by ▁Dam ▁opened ▁the