The Collaborative International Dictionary of English v.0.48:

Sluiceway \Sluice"way`\, n.
   An artificial channel into which water is let by a sluice;
   specifically, a trough constructed over the bed of a stream,
   so that logs, lumber, or rubbish can be floated down to some
   convenient place of delivery.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sluiceway
    n 1: conduit that carries a rapid flow of water controlled by a
         sluicegate [syn: sluice, sluiceway, penstock]