ivers ▁and ▁streams ▁ ▁Some what ▁to ▁the ▁north west ▁of ▁the ▁Nord h elle ▁is ▁the ▁source ▁of ▁the ▁O ester ▁( E bb eb ach ), ▁which ▁passes ▁the ▁mountain ▁to ▁the ▁north ▁before ▁collect ing ▁the ▁Er l me cke ▁– ▁a ▁trib ut ary ▁rising ▁east ▁of ▁the ▁sum mit ▁where ▁the ▁mountain ▁trans itions ▁to ▁the ▁Wald berg ▁– ▁near ▁Em mes za un ▁( H ers che id ). ▁R ough ly ▁south west ▁of ▁the ▁Nord h elle ▁in ▁the ▁transition ▁area ▁with ▁the ▁Groß er ▁H ahn ▁r ises ▁the ▁I h ne ▁trib ut ary ▁of ▁the ▁Sch male ▁Be cke ▁( Hom berger ▁Bach ). ▁ ▁Nature ▁res erves ▁ ▁There ▁are ▁several ▁nature ▁res erves ▁on ▁or ▁around ▁the ▁Nord h elle : ▁ ▁Auf ' m ▁E bbe ▁/ ▁E bb emo ore ▁Nature ▁Reserve ▁( CD DA ▁No .   1 6 2 2 9 4 ; ▁established ▁ 1 9 3 0 ; ▁ 6 . 6 6 4   km ² ), ▁which ▁runs ▁up ▁the ▁southern ▁fl ank ▁ ▁Wolf s bru ch ▁Nature ▁Reserve ▁( CD DA ▁No .   8 2 9 3 9 ; ▁ 1 9 3 0 ; ▁ 1 6 . 9 7   ha ), ▁on ▁the ▁eastern ▁mountains ide ▁ ▁Bra u ke ▁Nature ▁Reserve ▁( CD DA ▁No .   3 1 8 2 3 2 ; ▁ 1 9 9 5 ; ▁ 9 . 4 1