Created by nature, shaped by people

Rivers are large running waters created mainly by natural processes but often greatly altered by centuries of human activity.

What is a river?

We treat waterbodies shown on UK Ordnance Survey 1:25,000 scale maps with two blue lines as rivers. This refers to waters with a channel width of more than 8.25m.

People often assume that rivers are just their permanent channels. In fact, virtually all rivers would naturally also have a floodplain area where water flows intermittently – although this fact is often forgotten, or ignored.

There are about 90,000 km of rivers in UK, and they are found in all parts of the country. Only 3% of UK rivers are classed as High Status.

Shallow rocky river with mountains and a blue sky behind.

- The River Feshie in the Scottish Highlands is one of Britain's least modified rivers


of rivers in the UK


UK rivers classed as High status


of rivers in the UK


UK rivers classed as High status

What can you find living in a river?

The plants and animals living in rivers vary depending how steep and fast flowing the river is, and whether it has predominantly acid or alkaline water. In many places, pollution also has a big impact on what lives in rivers with many species eliminated, or their populations reduced. Rivers support the plants and animals that need running water.

For animals, this means species that depend on constantly high oxygen levels – like stoneflies and many (but not all) mayflies. It also includes filter feeders, like blackflies or net spinning caddis larvae, that depend on moving water to bring their food to them.

In the river margins – even in quite fast flowing upland rivers – there are many freshwater plants and animals that can live almost anywhere, as long as there is water. Plants like water mint and brooklime fall into this group, as do animals like the Common Water Slater and the Wandering Snail.

All rivers should have a good variety of fish in them – and in Britain this includes both coarse and salmonid fish. Rivers don’t have as wide a variety of water beetles as ponds, nor so many submerged water plants. Rivers do have specialist dragonflies and damselflies – like the White-legged Damselfly or the Club-tailed Dragonfly which are only occasionally found in riverside ponds.

Species directory
Close up of yellow and black dragonfly on a light green leaf.

- Common Clubtail dragonfly (c) Guido Gerding under licence from CC-BY-SA-3.0 (], via Wikimedia Commons

Why are rivers important?

Rivers are important because they can be among our richest freshwater habitats. They support species that absolutely depend on permanent running water.

These include salmon and other fish that need clean gravels to spawn on, stoneflies and mayflies that depend on constant high oxygen levels and cool water, river mosses, the invertebrate-eating Dipper and in the very best upland rivers, Freshwater Pearl Mussels.

Our policy work
freshwater pearl mussel

- Freshwater Pearl Mussel

How Freshwater Habitats Trust is helping rivers

Much of our work is at catchment scale. This means we focus on protecting the whole water environment, including the river and its tributaries.

In different parts of the country, we are mapping freshwater wildlife and water quality in a range of habitats, including rivers. This includes work to support rare and endangered species, like the Freshwater Pearl Mussel, which needs clean running water. Through our catchment work and research projects, we are working with landowners and partners to evaluate the benefits of natural flood management measures, such as leaky dams, tree hinging and debris dams on rivers.

Rivers are also a crucial element of our strategy to create the Freshwater Network, which includes restoring river floodplains.

The Freshwater Network
Debris dam on a river.

- Debris dam on the River Leck

Find out more about our work on rivers

Group of people walking down a hill through a field, with a large pond behind.
Working across the catchment

We co-host the River Thame, River Ock and New Forest catchment partnerships.

Find out more
Pond with tree reflected on the water, blue sky behind.
Water Friendly Farming

We’re evaluating the benefits of natural flood management measures in this farmed landscape in Leicestershire.

Water Friendly Farming
Aerial view of a landscape, including a meandering river and newly dug ponds.
The Freshwater Network

We’re creating wilder, wetter, cleaner, more connected habitats to reverse the decline in freshwater biodiversity.

Find out more