The water of the brook

Water over-abstraction in Cambridge

A sustainable water supply—for both the human population and the city’s chalk stream wildlife—is now a major concern in the City. The Cam Valley Forum has been documenting this for some years and the main issues are summarised on their website:

Cambridgeshire is the driest part of Britain, with nationally important chalk streams and highly variable rainfall. The Chalk aquifer that supplies 97% of our public water supplies is under unsustainable pressure: over-abstraction means that already it cannot keep our chalk streams running as they should through the year. Pollution of the water by faecal bacteria, nitrates and phosphates is becoming an increasing problem, and the pressures of increasing population, economic growth, intensive land management and climate change will only make a bad situation worse.

In his article, David Brooks provides some details on the water flow in Cherry Hinton Brook and gives some information on how this has changed over time.

The Cherry Hinton Brook has some of the characteristics of a Chalk stream. It emerges from the Zig Zag Chalk through a genuine Chalk spring at Giant's Grave, Cherry Hinton and flows over the Marly (clayey) Chalk at a nearly-constant rate. It is now recognised that in the longer term the Cambridge Water Company has pumped so much ground water from the Chalk aquifer that the water table has been lowered enough to reduce the discharge of this and other springs.

As an affiliate member of the Chalk Stream Aquifer Alliance Friends of Cherry Hinton Brook, along with Cam Valley Forum and other local and national groups, are helping to identify and implement solutions to this problem.

Cambridge City Council and Cambridge Water have commissioned a report: Greater Cambridge Chalk Stream Project report as an audit of chalk streams in the upper Cam catchment. It provides a brief overview for each river of the main issues affecting it and key opportunities. It also identifies some potential projects. These projects range from wellresearched plans which will be delivered in 2021, to project ideas and long-term ambitions.