The Rochdale Canal joins the Bridgewater at Potato Wharf. That's the Rochdale coming through the Arch. The Lock Keepers Cottage is just above the Arch. (The Arch was being Repaired when the Photo was Taken.) Beetham Tower now called Hilton Tower in the Background Manchester's Tallest Building.
This is where the Bridgewater and the Rochdale Canals join together. While underneath the River Medlock run underground.
This is the Giant Basin where the Excess Water goes down the Hole in to the River Medlock which run underground. What a Great Way to get and Keep the Canals Levels Stable.
The Giants Basin feeds excess water from The Canals of Bridgewater and Rochdale back down to the Medlock which runs underground which neatly solves a level problems in the canals.
Manchester is in the Middle of Three River's, The Irwell, Irk, and the Medlock. This is why the town it was so successful in processing cotton. The water is very soft. 85% of Cotton Goods in the Past was made in Manchester. In places like New Zealand all Supermarkets have a Manchester aisle even today. All cotton goods in the one aisle.
The River appears again from these Twin Arches as goes under a series of busy road junctions on it way to join the River Irwell.
The River once again surfaces from it's underground journey through Manchester.