The River Lee rises around Luton and flows to join the River Thames east of the Isle Of Dogs roughly opposite the Millennium Dome. For a substantial part of its length there are two separate channels — the 'canalised' River Lee Navigation and the old River Lea itself. In Lower Edmonton when we talk about the river it is typically the River Lee Navigation we mean. The actual River Lea would have flowed roughly down the middle of the huge William Girling Reservoir and the "River Lea Diversion" is away on the Chingford side. The River Lea formed the eastern boundary of Edmonton which is why on older maps you see the boundary marked through the middle of the reservoir. The boundary of Enfield has now been shifted to the east side of the reservoir along the diverted River Lea.
You will notice I have used two spellings. There is much debate over the "correct" spelling and it seems that neither of them is the original spelling which is Ley. To cut a long story short, Lee has been adopted for just about all "official" purposes over the last 400 years or so (River Lee Navigation, Lee Valley Regional Park) while Lea tends to be adopted for the original river. Where the canal and river channels merge for a length maps refer to the River Lee or Lea to hedge their bets. Upstream from the Hertford area only the spelling Lea is used because there is only the original course.
Walking from Picketts Lock (left) to Ponders End lock (one mile distant) the river is flanked by the golf course on the left and the overflow channels and then the high banks of the William Girling Reservoir on the right. Those tower blocks in the photo on the right are in South Street in Ponders End.
Roughly on the boundary the landscape changes abruptly to something more industrial (first two photos). As anyone walking the towpath needs to walk further to find an exit path I'll just show a photo of the marina thingy leading up to Ponders End Lock right.