Above: The River Chess in June 2025, a river whose story is a beacon of hope in the long struggle to restore our chalk streams

Chalks Streams First – as regular readers will know – is a radical but pragmatic way to realign abstraction pressure in chalk streams, allowing the streams “first” use of their water, without removing the water from the public supply network. 

The idea was conceived and theoretically tested by John Lawson using the catchments of the Colne and Lea as examples. I joined in with John to help give the idea traction with Ofwat, the EA and eNGOs. There is now a Chalk Streams First coalition of eNGOs who support the concept and variations on the idea have been absorbed into regional planning, albeit few have been fully realised as yet.

Chalk Streams First works by greatly reducing aquifer abstraction in chalk stream headwaters and upper valleys – the cheap and easy way to abstract water – and moving the point of abstraction to the lower, less environmentally sensitve reaches of the same catchments, where it is taken from the surface flow and recirculated, via reservoirs, treatment and network infrastructure to the places formerly supplied by the groundwater abstraction.

Across the full hydrological cycle a large % of the water not taken from the aquifer will manifest as surface flow (known as flow recovery) but that % is much higher in winter (over 100%) than summer (25% to 40%). Hence the need for the reservoir which stores that winter excess and becomes, essentially, a man-made version of the aquifer.

It’s the water resources verison of cakeism. Rivers and taps continue to flow.

There are a number of theoretical variations on this general concept of cakeism: for example, the upper valley groundwater abstraction could feasibly be replaced by lower valley groundwater abstraction where the rises and falls in the water table are much smaller, and the supply more reliable in summer. 

It is this version of the concept that is currently being developed by Affinity Water. Affinity Water’s central region operates largely to the north-west of London and historically has been very much reliant on chalk aquifer abstraction from the chalk hills of Bucks and Herts: the Misbourne, Colne, Lee and Stort units in the map below.

To date, Affinity – which supplies 970 million litres of water per day to almost 4-million people – has reduced its take from chalk groundwater sources by 100 Ml/d by investing in new assets and network reinforcement and increasing imports from Grafham and Ardleigh reservoirs.

Stream by stream these reductions have amounted to:

• Hughenden Stream – a 100% reduction of 1.6 Ml/d
• Misbourne – a 50% reduction of 13 Ml/d
• Upper Chess – a 100% reduction of 6.38 Ml/d
• Upper Gade – a 31% reduction of 6.4 Ml/d
• Ver – a 67% reduction of 28 Ml/d
• Upper Lea – a 27% reduction of 10.2 Ml/d
• Hiz and Oughton – a 13% reduction of 1.3 Ml/d
• Mimram – a 50% reduction of 9 Ml/d
• Beane – a 70% reduction of 16 Ml/d

Of course many of those reductions were from very high totals. For example the Ver’s once total abstraction of 42 Ml/d was well over half the catchment recharge in an average year, meaning the 15 Ml/d still abstracted remains a high % of the stream’s recharge. We (Chalk Streams First) have argued that “sustainable” abstraction should generally amount to no more than 10% of aquifer recharge, ideally less.

However, Affinity hasn’t finished. In AMP8 it will be cracking on with a further 35 Ml/d of reduction from the chalk streams feeding the Colne, including 14 Ml/d of license relocation following the Chalk Streams First principle, which is allowing Affinity to fast-forward these reductions before other strategic resource options (ie reservoirs and transfers) come online.

Planned reductions in AMP9 are also very encouraging, totalling 45 Ml/d.

Affinity deffo deserves credit for pursuing these reductions in the face of severe logistical dificulties and contortions. They inherited a system that was developed in a different era when the resource was thought to be more than abundant. Times have changed. Affinity Water must continue to supply water – its primary statuory duty – whilst finding an environmentally more sensitive way to do it.

The battle aint over, however. The ecological response of the streams will be carefully monitored and the inclination – I’m fairly sure of this – will be to suggest that the response has not been as good as expected. That’s because the economic forces and need to supply water are urgent and are only going one way but also because it is very difficult to tease apart all the environmental stresses on chalk streams and ascribe cause and effect to only one.

The real point is that to get the best value from the investments necessary to reduce and relocate abstraction we MUST also ensure that the water in the streams and aquifers is clean and that physical habitat is restored. Only when all three happen can we expect to see true ecological recovery.

Meanwhile, congrats and chapeau to Affinity Water, for engaging so positively with the chalk stream restoration strategy. The trout will thank you. Maybe one day, the salmon!