runnel (n.)

• aqueduct
• arroyo
• beck
• bed
• bourn
• branch
• brook
• brooklet
• bum
• burn
• canal
• channel
• creek
• crick
• culvert
• flume
• freshet
• gill
• gulch
• gully
• headrace
• kill
• midstream
• nullah
• race
• river
• rivulet
• run
• rundle
• sluice
• spillway
• stream
• streamlet
• swash
• tailrace
• wadi
• watercourse
• waterway
• waterworks