▁has ▁a ▁length ▁of ▁. ▁The ▁Pet it ▁S ag uen ay ▁River ▁success ively ▁cross es ▁" L ac ▁au ▁S able " ▁from ▁south ▁to ▁north ▁( length : ▁; ▁alt itude : ▁), ▁Lac ▁au ▁Bou le au ▁( Mont - É lie ) ▁( length : ▁; ▁alt itude : ▁) ▁and ▁the ▁eastern ▁part ▁of ▁Em m ura illé ▁Lake ▁( S ag ard ) ▁( length : ; ▁alt itude : ▁). ▁ ▁The ▁mouth ▁of ▁" L ac ▁au ▁S able " ▁is ▁located ▁at : ▁ ▁south - west ▁of ▁lac ▁D esch ê nes ; ▁ ▁south ▁of ▁the ▁village ▁center ▁Pet it - S ag uen ay ; ▁ ▁south ▁of ▁the ▁confl u ence ▁of ▁the ▁Pet it ▁S ag uen ay ▁River ▁and ▁" An se ▁du ▁Pet it ▁S ag uen ay ▁Bay " ▁located ▁on ▁the ▁south ▁shore ▁of ▁the ▁S ag uen ay ▁River . ▁ ▁From ▁the ▁mouth ▁of ▁" L ac ▁au ▁S able ", ▁the ▁current ▁desc ends ▁the ▁Pet it ▁S ag uen ay ▁River ▁for ▁ ▁north , ▁n ortheast , ▁then ▁north ▁to ▁the ▁south ▁bank ▁of ▁the ▁S ag uen ay ▁River ▁which ▁the ▁current ▁then ▁cross es ▁on ▁ ▁east wards ▁to ▁T ad ouss ac ▁where ▁this ▁last ▁river ▁flows ▁into ▁the ▁Saint ▁Lawrence ▁River . ▁ ▁Top onym y ▁ ▁The ▁to pon ym ▁" lac ▁au ▁S able " ▁was ▁formal ized ▁on ▁December ▁ 5 ,