A lovely song, and found quite often in tradition in England, Canada, the USA and Ireland; roughly in that order (Roud Folk Song Index number 987, Laws O15). Completely unrelated to the subject of this thread, however. There are two sets in the DT and one in the Forum:

THE GREEN MOSSY BANKS OF THE LEA  from Mackenzie's Ballads and Sea Songs From Nova Scotia.

THE GREEN MOSSY BANKS OF THE LEA (2)  from O'Lochlainn's More Irish Street Ballads.

Looking for 'The banks of the Lee'  Text and abc of the set recorded by Nic Jones (source unspecified).