Delvenau
It begins in Büchen , flows to the Elbe–Lübeck Canal near its confluence with the Elbe in Lauenburg . 
<triplet> Elbe–Lübeck Canal <subj> Elbe <obj> origin of the watercourse <triplet> Lauenburg <subj> Elbe–Lübeck Canal <obj> located in or next to body of water <subj> Elbe <obj> located in or next to body of water