Rivers and wetlands

Rivers and wetlands are precious habitats in the Chilterns, with crystal-clear chalk streams and the River Thames as highlights.

The River Thames forms the boundary between the two landscapes of the North Wessex Downs and the Chilterns. Throughout the years, its famous flowing waters have provided us with everything from transport and leisure to food and water. Yet, many other creatures value its resources too. Otters run along its riverbanks, water voles plop into its waters from their bankside burrows, herons stalk the edges where fish rest, bright yellow irises and kingcups bloom on its margins, dragonflies skim its surface, and the nodding bells of snake’s-head fritillaries adorn its riverside meadows.

Other wetland habitats in the Chilterns AONB include lakes, gravel and mineral extraction pits, reservoirs, canals, ponds and temporary waterbodies, all providing important wildlife habitat. Many ponds on farmland and common land were originally created to provide water for livestock, but now support a whole host of watery wildlife like newts, caddisflies, water lilies and starfruit.

The chalk aquifer underlying the Chiltern Hills supplies water to millions of people in South East England. It also supplies the bubbling surface waters and springs that flow into the Chilterns’ nine very precious chalk streams – a globally scarce habitat, of which there are just 300 in the world. Chalk streams are shallow, fast-flowing watercourses, with a gravel bed and low banks. They are home to some of the UK’s most endangered species, such as water vole, otter and brown trout. They also have a fascinating history and supported many thriving industries in the past.

Discover the Chilterns’ rivers and wetlands for yourself! Browse our interactive map to find a watery paradise near you or check out our Places to visit section for inspiration.

Please follow the Countryside Code and any rules for the place you are visiting when you’re out and about. Remember: RespectProtect and Enjoy – and help this special landscape and those who live and work here.

Types of rivers and wetlands in the Chilterns

Natural waterways course through the countryside, taking fallen rain and springwater down hillsides and onto floodplains. The Chilterns has several famous waterways, including the mighty River Thames, which runs through its heart. It also has nine precious chalk streams – watercourses that flow across chalk bedrock, often fed by underground or seasonal springs. These rivers and streams support a huge range of wildlife, from plants like yellow flag iris and water crowfoot, to mammals like water voles and otters, from birds like grey heron and kingfisher, to insects like emperor dragonflies and peacock butterflies.


These waterbodies are all made by human activity, whether drainage, water storage, channel modification, digging or quarrying. Despite this, they can support diverse and large numbers of species, in the same way that natural lakes and ponds can. Waterfowl and wading birds flock to flooded quarries and reservoirs, dragonflies and damselflies dance along canal margins, and small mammals feast in waterside vegetation and shrubs.

Lakes and ponds are waterbodies that come in all shapes and sizes. Ponds may be everything from large, permanent waterbodies, to smaller, seasonal ponds that dry up in the heat. Lakes are generally much larger, forming where water collects in hollows and basins, but are only those made by humans can be found in the Chilterns. Fish and amphibians live in the waters of lakes and ponds, and waterfowl and waders use the water and its margins. The edges of waterbodies often provide lush vegetation for invertebrates and mammals.

Fens form in low basins or valleys where drainage is poor (or has not been carried out by humans). As a result, they are water-logged and thick with reeds and tall herbs. Wetland plant species, such as rushes and sedges, dominate, and open pools attract myriad insects. Reedbeds are also damp swamps, forming a transitional habitat between water and land. They are typified by the golden-brown of common reeds standing tall above the water. Herons feed at the water’s edge, while reed buntings are warblers perch on the reeds. Water voles and otters frequent both these habitats.

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Wetland wildlife

There is so much wildlife to enjoy in the wetlands of the Chilterns – ducks dabble on lakes, rivers teem with trout, and frogs frolic among the bankside flowers. Explore our watery places through the seasons to find out where to go for wildlife, what to spot and what’s rare.

Why are rivers and wetlands important?

Wetlands don’t just provide food and shelter for plants and animals, but are an integral part of our whole environment. A healthy natural environment underpins the health and well-being of society and the economy. The natural resources – or ‘natural capital’ – of the Chilterns include its wetlands, alongside other features like habitats, species and soils. The benefits that we get from this natural capital are called ‘ecosystems services’. Our lakes, ponds, rivers, streams, reedbeds and floodplains provide a wide range of ecosystem services, including clean water, natural flood defences, pollination opportunities, carbon storage, recreation, health and well-being opportunities, and locally distinctive products.

From gravel extraction to fishing, navigation to irrigation, our wetlands have supported a range of thriving industries, and still do today. These human activities and industries have left a massive – often negative – mark on our wetland landscapes, although the positive benefits of working with nature, rather than against it, can also be seen in many places, for instance: extraction has left behind flooded pits, home to rare wetland birds; artificial canals criss-cross the countryside, offering leisure activities; over-managed watercourses are being restored to be wildlife-friendly; fishing is providing recreation opportunities and locally sourced food; and land drained for farming and development, is being allowed to regenerate as floodplain grasslands and traditional meadows.

Remember, we can all do our bit to help our wetlands by supporting wetland recreation businesses and buying local wetland products like wood, reeds and fish.

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Rivers and wetlands under threat

Wetlands are naturally evolving features of the landscape, but their important habitats and characteristics are being lost at an alarming rate due to climate change. There are many other threats to the survival of our wetland heritage, too, including pollution, habitat loss and invasive species. Find out how we are tackling these threats and how you can help.

Managing our rivers and wetlands

Protecting and managing our rivers and wetlands is one of the most important conservation activities in the AONB. They are part of the heritage of the area and include important and major rivers like the Thames, precious and rare chalk stream habitats, special flooded gravel and chalk pits home to a rich array of wetland wildlife. Find out more about how we look after our wetlands in the Chilterns AONB Management Plan 2019-2024.

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Chilterns’ Chalk Streams

The Chilterns’ chalk streams are so important that a special partnership uniting all the organisations with an interest in conserving them has been formed. Our Chilterns Chalk Streams project works with local people to improve river habitats, enhance access and enjoyment, and promote the sustainable use of water.

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The Management Plan for the Chilterns National Landscape

The Management Plan sets out the policies and actions to be followed by all stakeholders to conserve and enhance this special place. The current Plan (“the Chilterns AONB Management Plan 2019-24”) has been extended to March 2025 and is currently under review.