Soon after the start of Arc 1 at Hertford, you will encounter this curious building. It is the New Gauge House (1856), marking the abstraction point on the Lea Navigation where the New River begins. This is neither new (1613) nor a river…
but rather a 28 mile aqueduct to bring fresh water from the river Lea and captured springs here and elsewhere to Sadlers Wells in Islington.
The aqueduct follows the 100 foot contour, dropping slowly to deliver fresh water by gravity to London. The original course was a more winding 39 miles, with a gradient of 10cm drop per km (an impressive engineering feat) but it is somewhat straighter now, and terminates in the Woodberry Wetlands reservoir in Stoke Newington – and still supplies 8% of London’s water.