The River Lea is located in south-east England. It rises in Bedfordshire in the Chiltern Hills and flows south-east through Hertfordshire, along the Essex border and into Greater London, where it joins the Thames at Bow Creek. It is one of the largest rivers in London and the easternmost major tributary of the Thames. The river’s importance as a major east-west barrier and border tends to obscure its importance as a north-south trade route. Below Hertford, the river has been modified since medieval times to make it more navigable for ships between the Thames and East Hertfordshire and Essex, known as the Lee Navigation. This encouraged the development of industry on its banks. The navigable River Stort, its main tributary, joins it at Hoddesdon.
While the lower reaches of the River Lee remain somewhat polluted, its upper reaches and tributaries, classified as watercourses. They are the main source of drinking water for London. An artificial waterway known as the New River, opened in 1613, takes clean water for drinking purposes from the upper reaches of the river at Hertford and also takes water from the lower reaches.
The boundary of the River Lea and its main tributary, the Stort, has long been used as a political boundary. In the Iron Age, the valleys of the Lea and Stort formed a closely watched border zone between the Catuvellauns to the west and the eastern Trinovantes. It is believed that both rivers were the border between the core territory of the East Saxon Kingdom and its Central Saxon province.
