▁prime ▁location ▁for ▁fresh water ▁muss els . ▁ ▁Two ▁abandoned ▁oil ▁well s ▁can ▁be ▁found ▁on ▁the ▁island . ▁ ▁References ▁Nature ▁Tour ism ▁ ▁Category : Al leg hen y ▁Islands ▁W ilder ness ▁Category : Pro te cted ▁areas ▁of ▁Forest ▁County , ▁Pennsylvania ▁Category : Land forms ▁of ▁Forest ▁County , ▁Pennsylvania ▁Category : R iver ▁islands ▁of ▁Pennsylvania ▁Category : Is lands ▁of ▁the ▁Al leg hen y ▁River <0x0A> </s> ▁The ▁D rac ▁is ▁a ▁ ▁long ▁river ▁in ▁sout he astern ▁France . ▁It ▁is ▁a ▁left ▁trib ut ary ▁of ▁the ▁river ▁Is ère . ▁It ▁is ▁formed ▁at ▁the ▁confl u ence ▁of ▁the ▁D rac ▁No ir ▁and ▁the ▁D rac ▁Bl anc , ▁which ▁both ▁rise ▁in ▁the ▁southern ▁part ▁of ▁the ▁Mass if ▁des ▁É cr ins , ▁high ▁in ▁the ▁French ▁Al ps . ▁ ▁It ▁flows ▁through ▁several ▁res er voir s ▁on ▁its ▁course , ▁including ▁the ▁Lac ▁de ▁Monte yn ard - Av ignon et . ▁It ▁flows ▁into ▁the ▁Is ère ▁at ▁Gren o ble . ▁Its ▁major ▁trib ut ary ▁is ▁the ▁Roman che . ▁ ▁The ▁D rac ▁flows ▁through ▁the ▁following ▁depart ments ▁and ▁towns : ▁ ▁Haut es - Al pes : ▁Saint - B on net - en - Ch amps aur ▁ ▁Is ère : ▁Corps , ▁Gren o ble ▁ ▁The ▁average ▁flow ▁of ▁the ▁D rac ▁at ▁Font aine ▁is ▁, ▁with ▁the ▁highest ▁month ly ▁flows