About Us

A community organisation established to restore the flow to the upper River Ivel

The upper reaches of the River Ivel are dying.

The upper River Ivel is a perennial chalk stream, meaning it runs all year, supplied by groundwater in the chalk aquifer. In 2019 the river ran dry from its source at Ivel Springs to Radwell for the first time in living memory.

The RevIvel Association is made up of a committee that meets regularly and is supported by the Ivel Protection Association who are an association of angling clubs, Radwell Parish Meeting and North Herts District Council.

The Revivel Association is pleased to be part of the Chalk Aquifer Alliance, a network of chalk stream river groups campaigning for these precious environments.

The Chalk Aquifer Alliance (CAA) aim to  unite independent groups to protect our chalk streams.

RevIvel continue to be a part of the CAA working group and since the summer of 2020 the Chalk Aquifer Alliance have been able to present a series of talks pertinent to chalk streams and the challenges they face, thanks to the generosity of both Bury Water Meadows Group (who host the talks) and of each speaker

Each have been recorded and make a useful archive to dip into.

They can be found at   –   Talk Archive – Chalk Aquifer Alliance (wordpress.com)


  • Because the upper reaches of the River Ivel are dying
  • Because Affinity Water is taking too much from the source of the river or from the aquifer
  • Because the growth in population cannot be supported by existing water and sewerage systems
  • To inform and educate – to raise awareness of what is happening
  • To tackle the problems and do something about them


  • Too much water is being taken out of the aquifer
  • Historically there was enough water flow to drive multiple mills along the river
  • There is not a single river in the UK that meets the Environment Agency’s own ‘Good’ environmental standard!
  • There are only about 250 chalk streams in the world, fewer than there are Blue Whales or Coral Reefs! And 85% of them are in the UK
  • If we do not change our habits there will be no water in the river, and none to drink!


What makes our Chalk stream special and what does good look like.

Spring water comes from rainfall during the months October to March and is important to support the flow of crystal-clear spring water at the Ivel Springs. 
Rain in the spring and summer months is mostly taken up by plants (transpiration) or lost through evaporation on the chalk hills to the southeast of Letchworth/ Baldock (Clothall and Quickswood). 
However, throughout the autumn and winter months rain will soak into the soil and once field capacity is reached then rain will percolate into the chalk. 
The chalk is porous and fractured and will act like a giant “sponge” and rain will be stored in the chalk as “groundwater”. 
Groundwater levels and spring flow is at its greatest in the spring and at their lowest in early autumn.

Key features of natural, healthy chalk streams make them very special:

  1. The natural flow regime is relatively constant. Whilst it varies through the year, on a day-to-day basis it does not change much. Floods are rare and extreme low flows occur only in very dry years, usually as an effect of a dry previous winter.
  2. The water is filtered through the chalk and emerges crystal clear, with pH 7.4-8.0, high in minerals (esp calcium) and low in nutrients (phosphorus 0.01-0.03mg/l and nitrogen 0.2mg/l) and high in dissolved oxygen.
  3. The variable temperature of rainfall and snowmelt is averaged out as it filtered through the chalk and chalk spring water is about 11 degree Centigrade throughout the year.
All these features mean that a healthy chalk stream is a unique habitat for special plants, invertebrates, fish, birds, and mammals to thrive. 
Plants include water crowfoot (Ranunculus penicillatus subsp. pseudofluitans), water speedwell and watercress which provide vital habitat.
The pure waters and vegetation are home to invertebrates such a mayfly, stonefly, caddis, water shrimp and molluscs such as water snail. 
A healthy chalk stream should have fish such as bullheads, stickleback, minnows, and the iconic brown trout. 
In such an environment it should be common to see kingfishers flashing past you, hear the “plop” of the water vole as it enters the water and even catch a glimpse of an otter.
However, central to a healthy chalk stream is flow. 
Water crowfoot has an optimum growth at flow velocity of 0.3 – 0.5 m3/s and if flow is curtailed then it will die. 
Spawning brown trout need water that is roughly 0.9-1.2 metres deep and stream flow at a velocity of about 0.2 – 0.68 m3/s. 
Juvenile trout like water roughly greater than 15cms deep with stream flows between 0.1 – 0.4 m3/s.

This World Wildlife Fund 2min clip is a useful introduction to chalk streams. 

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