What is the Brighton Chalk Block aquifer?

An aquifer is a layer of rock underground that can store and move water. Across our Biosphere and the surrounding area, that aquifer is formed by the Brighton Chalk Block, a large body of chalk stretching roughly from the River Adur in the west to the River Ouse in the east and north towards the edge of the Downs.
Chalk is full of tiny cracks and spaces. Rain falling on the Downs can soak into these openings and move slowly down through the rock, where it is stored as groundwater. The chalk behaves a little like a sponge: it takes in water during wetter periods and releases it much more gradually.

That slow journey matters. The water pumped from the aquifer today may not have fallen as rain yesterday, last week or even last year. In many cases it has spent years travelling through and being filtered by the chalk before it becomes part of the water supply we use for drinking, cooking, washing and cleaning.

A healthy aquifer therefore supports more than our taps. It contributes to clean and reliable water, local biodiversity and ecosystems, and the long-term resilience of communities across the area.

Making the hidden water beneath us easier to understand

Groundwater can feel mysterious precisely because it is out of sight. But connecting what happens on the surface with the water stored below us is a powerful way to understand why aquifer protection matters.

The Aquifer Project (TAP) has developed free resources for schools, families, youth groups and anyone interested in learning more about the Brighton Chalk Block aquifer. These include a short ‘What is an aquifer?’ explainer video, printable drawing and colouring activities, and hands-on activities that show how water passes through different layers of the ground.
One activity is to build an edible aquifer using everyday ingredients. By creating layers that represent soil and rock, adding ‘rain’ and watching how water moves through the model, learners can see how groundwater is stored, how slowly it travels and how pollution at the surface can eventually reach the water below.

A water-use calculator can extend that learning into everyday life by showing how much water we use and opening up conversations about water saving, groundwater recharge and the importance of protecting a resource that is replenished gradually rather than instantly.

How is the aquifer at risk?

Being underground does not protect the aquifer from what happens above it. Rainwater can carry pollutants from the surface down through the chalk and into groundwater. Road run-off can contain oil, fuel, metals and tyre particles; chemicals used in homes, gardens and industry can enter the water system; fertilisers and pesticides can be washed from land; and sewer leaks or misconnections can send polluted water in the wrong direction.

Once contaminants reach groundwater, removing them can be difficult and expensive. Preventing pollution before it reaches the aquifer is therefore an important part of protecting local water quality. The way we cover the ground also matters. Roads, pavements, patios and car parks reduce the amount of rain that can soak naturally into the soil. Instead, water is moved rapidly across hard surfaces and into drains and waterways, often collecting pollutants along the way. This gives the aquifer fewer opportunities to recharge and can increase pressure on surface drainage during heavy rainfall. Water demand is another part of the picture. Groundwater moves slowly and the aquifer takes time to refill. When water is used faster than the system can comfortably replenish it, extra pressure is placed both on the water resource itself and on habitats that depend on healthy groundwater.

Protecting the aquifer through local action

Across The Living Coast, a range of projects are already helping to protect groundwater, restore water-related habitats and improve the way rain moves through the landscape. At Wild Park, polluted road run-off is intercepted and passed through a nature-based system of swales and planted basins. These features slow the water, help filter pollutants and support safer infiltration into the chalk, while also creating richer habitat for wildlife and a more attractive space for people

Seven Sisters National Nature Reserve.The landscape around Seven Sisters demonstrates the close relationship between chalk landscapes, groundwater and the natural environment. Protecting the land above the aquifer helps protect the water stored beneath it.

Changing Chalk: Greening the Cities. This work brings elements of chalk grassland into urban areas through pollinator banks, wildflower spaces and community planting, reconnecting neighbourhoods with the chalk landscape around them.

Changing Chalk: Wilding Waterhall. At Waterhall on the edge of Brighton, chalk grassland restoration, ecological monitoring, volunteering and grazing are helping bring a large area of the Downs back to ecological health.

Downs to the Sea, including Falmer Pond.This partnership supports the recovery of ponds, wetlands and waterways while helping communities connect with water in the landscape through conservation and engagement activities.

SuDS in Schools. Rain gardens and other sustainable drainage features in school grounds hold back rainfall, reduce run-off, create habitat and give children a practical way to learn how water moves through the landscape.

Lewes Railway Land Wildlife Trust. Wetlands, ponds and reedbeds at the Railway Land Nature Reserve provide valuable habitat and opportunities for people to learn about healthy water systems in an urban setting.

Cockshut Stream restoration. Restoration of this rare chalk stream is creating wetland habitat and helping the wider water landscape become healthier and more resilient.

Love Our Ouse. Community action around the River Ouse brings people together to celebrate the river and take practical steps to care for it.

Rain gardens across our communities. Rain gardens catch water close to where it falls, slowing it down, allowing more of it to soak naturally into the ground and creating small but valuable areas of habitat.

Protecting groundwater is not limited to large infrastructure or conservation projects. Everyday choices can also help reduce pollution, support recharge and improve the way water moves through our towns and neighbourhoods. Use less water at home where you can.

Choose permeable surfaces and allow rain to soak into the ground rather than immediately running into drains.

Avoid allowing oils, paints, wipes or other pollutants to enter drains.

Think carefully about chemicals used in gardens and on driveways.

Create a rain garden or use planters and planted areas to catch and slow rainfall.

Grow chalk wildflowers and support pollinators.

Join local volunteering, river-care, pond-restoration or habitat-management activities

Talk about groundwater and help others understand that what happens above ground affects the water below.

The Brighton Chalk Block aquifer may be hidden, but it connects our homes, streets, schools, farms, wildlife and the Downs. Understanding that connection is the first step towards protecting it. The more we understand where our water comes from and how our actions affect it, the better equipped we are to look after this precious local resource for people and nature.

Useful resources

The Aquifer Project:
https://thelivingcoast.org.uk/tap

Get Water Fit water-use calculator: https://www.savewatersavemoney.co.uk/getwaterfit/

Wild Park Rainscape:
https://thelivingcoast.org.uk/projects/tap/wild-park-rainscape

Changing Chalk: Greening the Cities: https://thelivingcoast.org.uk/project/changing-chalk-greening-the-cities

Changing Chalk: Wilding Waterhall: https://thelivingcoast.org.uk/project/changing-chalk-wilding-waterhall-2

Downs to the Sea:
https://www.southdowns.gov.uk/celebrating-a-year-of-the-downs-to-the-sea-project/ 

Lewes Railway Land Wildlife Trust:
https://www.railwaylandproject.org/the-nature-reserve/ 

Cockshut Stream:
https://www.cockshutstream.org/ 

Love Our Ouse:
https://loveourouse.org/