Before 1600 London’s water supply was limited to the River Thames, local streams, wells and springs. These sources, often contaminated, were largely distributed by sellers carrying water in wooden buckets. In 1606 a Parliamentary Act granted the Corporation of London the power to make a “New River for bringing water to London from Chadwell and Amwell in Hertfordshire”.
The New River is a critical and complex component of Thames Water’s Lee Valley Raw and Stored Water System, conveying raw water abstracted from the River Lee and some forty boreholes to three water treatment works and the storage reservoirs of the lower Lee Valley. Full utilisation of the available water resources depends on the capacity of the New River to convey the flow, and the capacity of major tunnel and pipe mains to transfer flow from the river.
In 2012, Thames Water produced a detailed hydraulic model of the entire New River system in order to better understand the capacity of the system and improve operation of the river. The model was developed for the Flood Modeller 1D solver and covers the full present-day length of the river and over 40 individual hydraulic structures, tunnels and pipe mains.
The model was built from record drawings, some more than 130 years old themselves, and data collected from site inspections and a walkover survey of the entire 36km length of the river.
The model was calibrated using data collected from a river flow gauging exercise and water level measurements at key locations along the river. In addition, field trials were carried out to determine by experiment the capacity of the King George Transfer Tunnel – a 1.8m diameter 3km long tunnel connecting the New River to the King George V reservoir – and the Amhurst Main – a 36” diameter, 3.6km main connecting the New River to Coppermills WTW.
The calibrated model has been used to determine the capacity of the system under a range of operational scenarios including drought conditions and various combinations of treatment works demand and reservoir transfers.
This has led to a better understanding of the operational constraints to borehole operation along the New River and identified opportunities to improve the operation of the system and maximise water resource utilisation whilst preventing flooding and minimising losses.