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We're proud of the great variety of wildlife living on our canals and rivers, from smooth newts to mighty oaks. Take a look at the biodiversity of our wonderful waterways.

Biodiversity simply means the variety of life within a particular habitat. All of that life is interdependent and any small changes can have a big effect.

That's why we have a team of ecologists who work across the country to protect and monitor life along the canals and rivers. Amongst other things, they give us advice on projects that could help a vulnerable species, and they make sure any construction or repair work we do isn't disrupting the delicate balance of an ecosystem.

Senior ecologist, Paul Wilkinson, chooses a few of the birds, mammals, insects, amphibians, trees, fish and plants that make up the biodiversity on our waterways.

Common toads

Unlike common frogs that need to keep their skins moist, common toads can travel much further away from water, to often quite dry habitats.

Toads are being found breeding in our waterways more and more. This is partly because their tadpoles are distasteful and fish avoid eating them. It's also because our canals usually have a constant supply of water from our reservoirs, which means they act as a reliable year-round home for toads.

Toads are long lived, so do not have to breed every year. Sadly their biggest threat tends to be getting run over as they cross and congregate on roads.

European otters

European otters are a great conservation success story. They suffered a catastrophic decline of around 90% in the 1970s. This was mostly due to the use of the now banned DDT pesticide that entered the otter's food chain, with devastating effects.

Otters are now back in almost all their previous areas of distribution, thanks to improvements in water quality and our waterways recovering their diversity.

Using data from DNA studies, we think we have about seven to nine otters on our West Midlands canal network.

Twaite shad

Now one of the UK's rarest fish, hundreds of thousands of twaite shad used to breed on the River Severn. The introduction of weirs in the 19 th century meant that the shad couldn't reach their spawning grounds further up the river, so their numbers declined dramatically.

Our Unlocking the Severn project is building six 'fish passes' that will enable the shad, and other fish species, to swim around weirs and establish themselves again.

Azolla

Also known as fairy moss or water fern, azolla isn't a true moss, but an aquatic fern. It grows very rapidly, making it one of the most troublesome invasive plants.

Originally from the Americas, it can now be found on our waterways, often in large clumps. We're using azolla weevils to bring the plant back under control.

Warmer weather caused by climate change may increase the distribution of this plant around the UK. But that might not be an entirely bad thing, because azolla has the ability to 'fix' nitrogen and carbon dioxide (absorb them from the air and use them in the soil). So these plants could play a role in the future in storing excess carbon dioxide that has built up in the atmosphere.

During the summer, females congregate in maternal colonies to keep themselves safe and to use their body temperatures to warm the roost during cold periods. Bats usually only produce a single youngster, a 'pup'.

Smooth newts

The smooth newt appears to be doing well on our canals. Unlike its larger and more infamous relative, the great crested newt, the smooth newt's tadpoles usually hide away to avoid being eaten by fish.

Smooth newts are susceptible to extreme weather conditions though. A dry or cold period in spring can have a big impact on their ability to breed in that year.

Wild cranberry

Can you believe that wild cranberry is a survivor from the last glacial period? It can still be found in a few special places, including the edges of some canals where there are acidic soils.

Rare and vulnerable, this plant is one of the species that could suffer in the future because of rising temperatures and periods of drought caused by climate change.

Kingfishers

My heart always beats a little faster when I'm lucky enough to see the electric blue flash of a kingfisher flying along our waterways.

Climate change can affect this species in several ways. Milder winters often help more birds survive, because canals and rivers don't freeze over and prevent them from feeding. However, flash floods during the breeding season can be disastrous, flooding out nest chambers in the banks of our waterways.

Humans

I've saved the most influential form of life along our canals and rivers for last. It's definitely us humans.

Research has shown that being by the water is great for our wellbeing, whether we're enjoying a boat trip, fishing or just taking a moment to sit and listen to nature. But, whatever we're doing, it's so important to be aware of the biodiversity around us.

Our species has the ability and responsibility to decide whether to take wildlife into the future with us, or leave it behind in the history books. Being respectful of the environment and wildlife, and taking our litter home with us, will help make sure that our waterways continue to thrive in the years to come.

Last date edited: 11 February 2021

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Celebrating the variety of life | Canal & River Trust

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We're proud of the great variety of wildlife living on our canals and rivers, from smooth newts to mighty oaks. Take a look at the biodiversity of our wonderful waterways. Biodiversity simply means the variety of life within a particular habitat. All of that life is interdependent and any small changes can have a big effect.

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Upper course, Middle course, Lower course, Source , Mouth, Oxbow lake, Tributary, Sediment, Meander.

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Source - The beginning of a river , Spring - Water that comes out of the ground at the top of a mountain , Stream - A small river, River - A large natural flow of water , Floodplain - Area of flat land either side of the river likely to flood , Tributary - A stream or river that joins another river , Confluence - The point where a tributary joins a river , Meander - A bend in a river , Oxbow Lake - A lake created when a meander is cut off , Mouth - Place where the river meets the sea , Drainage basin - The area of land drained by a river, Waterfall - Where a band of hard rock lies over a softer one, creating an overhang via erosion., Delta - Where a river carrying a large amount of sediment meets lake or the sea,

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Source - The beginning of a river , Spring - Water that comes out of the ground at the top of a mountain , Stream - A small river, River - A large natural flow of water , Floodplain - Area of flat land either side of the river likely

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•  Water Science School HOME  •  Surface Water topics  •

Rivers, Streams, and Creeks

Glacier melting in springtime causes high streamflows. Bow River Falls, downstream from the Bow Glacier in Banff, Canada.
Credit: Banff Holidays

Rivers? Streams? Creeks? They are all names for water flowing on the Earth's surface. As far as our Water Science site is concerned, they are pretty much interchangeable. I tend to think of creeks as the smallest of the three, with streams being in the middle, and rivers being the largest.

Most of the water you see flowing in rivers comes from precipitation runoff from the land surface alongside the river. Of course, not all runoff ends up in rivers. Some of it evaporates on the journey downslope, can be diverted and used by people for their uses, and can even be lapped up by thirsty animals. Rivers flow through valleys in the landscape with ridges of higher land separating the valleys. The area of land between ridges that collects precipitation is a watershed or drainage basin. Most, but not all, precipitation that falls in a watershed runs off directly into rivers - part of it soaks into the ground to recharge groundwater aquifers, some of which can then seep back into riverbeds.

What is a river?

A river forms from water moving from a higher elevation to a lower elevation, all due to gravity. When rain falls on the land, it either seeps into the ground or becomes runoff, which flows downhill into rivers and lakes, on its journey towards the seas. In most landscapes the land is not perfectly flat—it slopes downhill in some direction. Flowing water finds its way downhill initially as small creeks. As small creeks flow downhill they merge to form larger streams and rivers. Rivers eventually end up flowing into the oceans. If water flows to a place that is surrounded by higher land on all sides, a lake will form. If people have built a dam to hinder a river's flow, the lake that forms is a reservoir.

Rivers serve many uses

The Chattahoochee River, Atlanta, Georgia, USA. The river serves many purposes, from drinking water to wildlife habitat to a recreation spot for the whole city.
Credit: National Park Service

The phrase "river of life" is not just a random set of words. Rivers have been essential not only to humans, but to all life on earth, ever since life began. Plants and animals grow and congregate around rivers simply because water is so essential to all life. It might seem that rivers happen to run through many cities in the world, but it is not that the rivers go through the city, but rather that the city was built and grew up around the river. For humans, rivers are diverted for flood control, irrigation, power generation, public and municipal uses, and even waste disposal.

Are rivers one of your favorite places?
If so or if not, why not vote for your favorite water body in our Activity Center!

Where does the water in rivers come from?

Large rivers don't start off large at all, but are the result of much smaller tributaries, creeks, and streams combining, just as tiny capillaries in your body merge to form larger blood-carrying arteries and veins. The mighty river featured in this image is called the Yarlung Tsangpo as it courses through the Tibetan Autonomous Region of China.
Credit: NASA

The most simplistic answer is that all the water in a river comes from the sky—and that is certainly true, as streamflow is one part of the water cycle. It is also true that most of the water flowing in rivers comes from precipitation runoff from the surrounding landscape (watershed).

But, the water in a river doesn't all come from surface runoff. Rain falling on the land also seeps into the Earth to form groundwater. At a certain depth below the land surface, called the water table, the ground becomes saturated with water. If a river bank happens to cut into this saturated layer, as most rivers do, then water will seep out of the ground into the river. Groundwater seepage can sometimes be seen when water-bearing layers emerge on the land surface, or even on a driveway!

Look at the diagram below. The ground below the water table (the blue area), is saturated, whereas the ground above (the gray area) is not. The top layer (unsaturated soil/rock material) is usually wet, but not totally saturated. Saturated, water-bearing materials often exist in horizontal layers beneath the land surface. Since rivers, in time, may cut vertically into the ground as they flow, the water-bearing layers of rock can become exposed on the river banks. Thus, some of the water in rivers is attributed to flow coming out of the banks. This is why even during droughts there is usually some water in streams.

In the diagram you can see how the ground below the water table (the blue area) is saturated with water. The "unsaturated zone" above the water table (the gray area) still contains water (after all, plants' roots live in this area), but it is not totally saturated with water. You can see this in the two drawings at the bottom of the diagram, which show a close-up of how water is stored in-between underground rock particles.

Where does the water in rivers go?

Like everything else on (and in) the Earth, water obeys the rules of gravity and tries to get to the center of the Earth (did you imagine that every molecule in your body is trying to do this, also?). So, the water in rivers flows downhill, with the ultimate goal of flowing into the oceans, which are at sea level. River water may end up in a lake or reservoir, in a pipe aimed at Farmer Joe's corn stalks, in a local swimming pool, or in your drinking glass, but much of it eventually ends up back in the oceans, where it rejoins the water cycle, which is ALWAYS in progress.

The "Mighty Colorado River" ends up dry

Endpoint of the Colorado River, Mexico. Less than 80 years ago, the mighty Colorado River flowed unhindered from northern Colorado through the Grand Canyon, Arizona, and Mexico before pouring into the Gulf of California. But as this NASA Earth Observatory satellite photo from September 2000 shows, irrigation and urban water needs now prevent the river from reaching its final destination. Rather, the Colorado River just disappears into the desert sands. The Colorado River can be seen in dark blue at the topmost central part of this image. The river comes to an end just south of the multicolored patchwork of farmlands in the northwestern corner of the image and then fans out at the base of the Sierra de Juarez Mountains. Only about 10 percent of all the water that flows into the Colorado River makes it into Mexico and most of that is used by the Mexican people for farming.
Credit: NASA Earth Observatory

One river that doesn't participate anymore in this natural water-cycle process is the mighty Colorado River, flowing from Colorado to the Gulf of California in Mexico. The Colorado River certainly starts out as mighty—mighty enough to have carved out the Grand Canyon—but nowadays it does not even end as a trickle. Whereas it once flowed into a large marshy area at the Gulf of California, today it literally disappears in the farmlands at the base of the Sierra de Juarez Mountains in Mexico. As the Colorado River flows through the desert Southwest, it gets used and used by millions of thirsty residents and for crop irrigation; used until there is nothing left. In this satellite view of the "exit point" of the Colorado River, the river itself is the dark blue patch at the top.

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Rivers, Streams, and Creeks | U.S. Geological Survey

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Rivers? Streams? Creeks? These are all names for water flowing on the Earth’s surface. Whatever you call them and no matter how large they are, they are invaluable for all life on Earth and are important components of the Earth’s water cycle.

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Check out all the different types of rivers here!

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Intro video to Rivers

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Rivers always flow downhill because of gravity. Find out more with Bitesize KS2 Geography.