The Lee Navigation is a canalised river incorporating the River Lea. It flows from Hertford Castle Weir to the River Thames at Bow Creek; its first lock is Hertford Lock and its last Bow Locks.

The River Lea is in the East of England and Greater London. It originates in Bedfordshire, in the Chiltern Hills, and flows southeast through Hertfordshire, along the Essex border and into Greater London, to meet the River Thames at Bow Creek. It is one of the largest rivers in London and the easternmost major tributary of the Thames.