Precious Water

Pure Clean Water

Pure Clean Water is a film about the Hobson's Brook, one of our rare and precious chalk streams. Our screening at Eddington on Thursday 25th Jan was sold out. Tony Eva (the producer) took questions afterwards and delegated some to Daniel Clark from Cambridge Water Company. Water Resources East was there too, Water Sensitive Cambridge and Wildlife Trusts.

In the film, we learn that Cambridge Water needs to reduce abstraction from the chalk by more than half in order to allow the streams to recover. So even were the population of Cambridge steady, we need to reduce consumption, and Cambridge Water needs to reduce leakage and we need new supply from somewhere such as the Fens Reservoir. However this already been decades in planning and proposales are still 'at an early stage'.

Meanwhile, Michael Gove is determined that Cambridge needs to double in size with another 150,000 homes (there are currently 120,000 in Greater Cambridge).

Water saving discussions often showcase Eddington as an exemplar development, designed to use only 80 litres/person/day which is 43% less than average. However, Eddington's savings rely on a secondary water supply taking water stored in the lake for use in toilets and washing machines and this supply is still not commissioned because the Drinking Water Inspectorate wants the water treated to drinking water quality (X thread here.)

Pure Clean Water - sold out at Eddington on 25/1/2024. It tells the story of Hobson's Brook, once the main source of drinking water for the Cambridge now only flowing with help from tap water injected directly into the chalk at Nine Wells.

More screenings for the film are listed here.

Enviroment Agency rules that Cambridge must reduce water abstraction

Water supply in Cambridge is an increasingly critical issue. Supply is tight and the Environment Agency has ruled that Cambridge Water must reduce abstraction of water from the chalk aquifers to protect our precious chalk streams. As of July 2021 we are officially a water stressed area. The Environment Agency has objected to several new housing schemes because of projected increase in water demand (Water supply fears prompt first housing objections - BBC, June 2-23). You can read a summary of Cambridge Water's current water resource plans here. These include drastic reductions in leakage and also in per capita consumption from around 140 litres/person/day down to 110. That means us!

Precious water videos

Watch our four short videos about the conflict between our water use and protecting our precious streams and rivers (including the Cam) - and what we can do about them. We made them for Earth Optimism 2021.

View Stephen Tomkins's talk on "Safeguarding our local water resources" here.

Here in Cambridge our water come from underground, mostly from the chalk under the Gog Magog Hills. This is a great resource as it acts as a giant reservoir, plus the water is filtered naturally by the chalk as it flows down into the aquifer. However, the same aquifer feeds streams that provide important habitat for wildlife. If the level drops too far then those streams can dry up - as they did in summer 2019. The flow in the River Cam was reduced to a trickle too for the same reason. It only takes one or two dry winters for this to happen. See this demo for how our water use affects the chalk streams.

Is climate change to blame?

Not entirely, though it definitely makes it worse. Climate change brings extreme weather of all kinds:

  • More heavy downpours . When rain comes in torrents, the ground cannot absorb it fast enough and it runs off into the rivers very quickly. We also get flash floods. Water that is not absorbed into the ground is wasted as far as the chalk is concerned.
  • Longer growing season. During the growing season most rain is used by plants – either in our gardens, on farmland or in the wild. The warmer weather means growing seasons are longer and the winter period when the aquifer fills up again is shorter
  • Hotter summers. When the weather is hot we use more water – to keep ourselves clean, to water the garden and to have fun. One medium sized paddling pool can double your family’s water use for the day.

What can we do?

The main thing is to use less water, both at home and in the garden. Here are some tips but there are links to more help on the Links page.

  • Fix dripping taps
  • Do not leave the tap running while washing vegetables or washing up - use a bowl
  • Get a water butt - plants prefer rainwater anyway
  • Take shorter showers
  • See how you could use less water

Chalk streams

Photograph: Yvonne Chamberlain © 2018
Source: the Waterlight Project

Ruth Hawksley (Wildlife Trust BCN) says: These habitats are very rare, our local equivalent of rainforests... It's their "special water" that makes chalk streams important - that water has been slowly filtered through the chalk so that by the time it emerges at the springs that start chalk streams, it is crystal clear, low in nutrients and pollutants, and at a fairly stable temperature .... All these conditions allow plants and invertebrates to thrive that you might not find in other places. These attract larger creatures such as kingfisher, otter, and water vole to create a diverse community.

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