Original subtitles

NARRATOR: Earth's great rivers...

..make extraordinary journeys...

..carving through continents,

feeding and connecting life...

..nurturing culture...

..providing a place for adventure.

From the frozen wilderness of the Yukon...

..to the tropical heat of the Zambezi...

HIPPO GROANS

..and the magical, hidden worlds of the Danube.

Great rivers are the lifeblood of planet Earth.

The majestic Danube...

..almost 3,000 kilometres long, from source to sea...

..running through the heart of Europe.

So much more than a single river.

The Danube is a giant network of water,

reaching out across the continent.

Flowing east from Germany and Austria,

all the way to Romania and the Black Sea.

Its tributaries gather water from 19 countries...

..making it the most international river on Earth.

On its journey, it will cross formidable landscapes

and ancient kingdoms...

..revealing glorious riches

and magical surprises.

But to follow the ever-changing face of this unique river...

..we start...

..at the very top.

Over 4,000 metres above sea level,

Piz Bernina Mountain in Switzerland

is the highest point of the entire Danube system.

Here, 800 million tonnes of water

is locked in...as ice.

Seven kilometres long and 250 metres deep,

the Morteratsch glacier, for most of the year,

is covered in deep snow.

But when temperatures rise in spring,

and conditions are just right...

..there's a window of opportunity.

WOMAN: Running keeps me alive.

It connects me with nature and connects me with my own spirit.

NARRATOR: Anne-Marie Flammersfeld has spent most of her life running

the world's toughest landscapes.

Today, she is seizing her moment

to run on the frozen headwaters of the Danube.

ANNE-MARIE: Running on a frozen river, it's something really weird

because it's only there in a special period of time.

NARRATOR: It looks beautiful,

but looks can be deceiving.

ANNE-MARIE: Even in the summertime, running on a glacier is really dangerous.

You don't know where the crevasses are.

When you fall into a crevasse, you can fall for three or five metres.

NARRATOR: So it pays to follow a planned route.

I always try to look for the best line when I run downhill

because I run downhill really fast,

and I really enjoy it, and then my eyes are concentrated

on every step and, tak, tak, tak.

And, uh, yeah, this is most of the fun.

NARRATOR: As she nears the base of the glacier...

..there's a glimpse of the true power locked up in the ice.

ANNE-MARIE: When you look into it and you see that the water

is coming from somewhere

and you think, "Ah, it's a river."

NARRATOR: Beneath the glacier,

the headwaters of the Danube are on the move.

More than a quarter of the river's water

comes from the Alps.

And, in spring, it becomes an unstoppable force of nature...

..fuelling the flow of the Danube across the continent,

all the way to the Black Sea.

Its journey...

..has only just begun.

Just a few kilometres away,

on the slopes of the valley below...

..the melting snow...

..makes way for new beginnings...

..revealing...

..someone's home.

Inside is a creature who has been waiting to come out...

..for nearly eight months.

A male alpine marmot.

They may seem small,

but, growing up to 8kg,

these are the heavyweights of the squirrel family.

Winter has not been easy on him and his kind.

Alpine marmots lose about a third of their body weight,

stuck in their burrows during winter.

Now, he needs to fatten up.

The melting snow has uncovered valuable food.

Marmots eat grasses, flowers,

and even a worm or two...

..if they can find them.

But there's a problem -

other families live here, too.

With only so much food to go around,

he'll need to defend his territory.

And when it comes to protecting home,

marmots mean business.

An intruder approaches.

It's time to go on the offensive.

To get an advantage...

..marmots rise up and stand tall.

Here in the valley, it's hand-to-hand combat...

..each pushing and grappling.

Now, keeping your footing is everything.

But just when the coast seems clear,

there's more danger.

The heat from the sun Now causes giant icicles

to fall from frozen waterfalls.

A blow from one of these would spell disaster.

Crisis over.

In the valley of the marmots,

life is looking good.

As the meltwaters run on...

..they join countless other streams and tributaries...

..flowing from all corners of the Danube system.

Passing through a myriad of habitats,

some of which hide secret wonders.

In the forests of Bosnia,

one Danube tributary has a very different source.

These crystal clear waters are fed by underground springs...

..creating a magical water world.

Legend has it that the Romans were so stunned by this river's beauty

they named it Una, meaning "The One."

While the water may look clear,

it's full of dissolved minerals from the limestone below,

producing a special kind of river

with miniature waterfalls and pools.

As water flows over moss and other plants,

the dissolved minerals are gradually absorbed

and collected by this natural sponge,

which hardens and builds...

..eventually forming whole new waterfalls.

It's like something from a fairy tale.

But not everything to see here is above the water.

Below, there's a party underway.

The nutrient and oxygen-rich headwaters of the Danube

create the perfect place to gather and search for food.

Golden shoals of barbel

mix with graceful grayling, and busy trout.

Many use these fresh waters to spawn...

..including one species

found nowhere else on Earth.

Each spring, if you look carefully,

you'll find one of the river's top predators.

The huchen, also known as the Danube salmon,

can grow over a metre long.

The largest freshwater salmon in the world.

Today, this pair are showing their softer side.

With her powerful tail,

the female sweeps away the gravel

to make a small depression in the riverbed.

A nest in which to lay her eggs.

Very soon, the riverbed looks like it's had a spring clean.

The male joins her to mate...

..and guards her from any unwanted attention.

But then...

..perhaps it's best to leave these giant predators to it.

The secret waters of the Danube provide a bounty

of opportunity for life.

And where there are fish...

..others will surely follow.

Today, Zdena Gavranovic is hoping to catch a fish

that thrives in crystal clear waters,

the trout.

She starts by making some fishing flies.

ZDENA IN CROATIAN:

NARRATOR: Her aim is to make the perfect insect...

..something that might just trick a trout to eat it.

ZDENA IN CROATIAN:

NARRATOR: Tiny feathers for the wings and silk for the body.

Solid enough to look the part,

yet delicate enough to cast.

Now, time to put them to use.

First, she casts out her line...

..with a loop in the air.

Released on to the water as light as she can...

..placing the fly to entice her quarry.

Fly fishing is a special kind of fishing.

ZDENA IN CROATIAN:

NARRATOR: Timing and rhythm are everything.

Each cast lets out a little more line...

..a little more hope.

ZDENA IN CROATIAN:

NARRATOR: No luck this time, not that it matters.

When a river is as beautiful as this,

that is rewarding enough.

While some are drawn to the tranquillity of the river,

the waters of the Danube constantly change.

In Slovenia, one of the Danube's largest tributaries,

the Sava offers an entirely different experience.

MAN: Woohoo-hoo!

NARRATOR: Like the rushing waters around him,

kayaker Rok Rozman finds a freedom here.

But it's not without risk.

ROK: There might be trees in the rapids,

which can be really dangerous.

There's some rocks that produce siphons.

So, like old people said,

the river is full of traps.

But, at the same time, the river is full of joy.

People who meet the river in a kayak

will always see the river differently.

NARRATOR: For Rok, who is also a biologist,

rivers bring so much more than just enjoyment.

ROK: Cos the river has the most abundance in diversity

and life out of any habitat, you know?

Transporting nutrients, water, energy,

it's the most important part of nature.

NARRATOR: And when faced with the pressures of life,

Rok also believes the river can help.

If you have problems,

you can go and talk to the psychiatrist,

or you can go and sit next to the river.

It's up to you what's nicer, cheaper, and better.

NARRATOR: As they flow down from headwaters and alpine valleys,

the Danube tributaries finally come together

to become this great river.

Towns...

farmland...

..and cities begin to line its route.

Over thousands of years, people have settled on its banks

and have tamed the river...

..straightened and engineered

to help protect against annual flooding.

But there are still wild places here.

Just outside Austria's capital, Vienna,

lies Donau-Auen National Park.

A strip of protected forest and wetland

on the banks of the Danube...

..home to some extraordinary creatures.

EARTH CRACKLES

A baby European pond turtle.

Buried as an egg four months ago,

it's now hatched and free.

Its mother chose a nesting spot that would be safe from flooding...

..but now it's far away from water.

And this tiny creature needs to go on an epic journey...

..all on its own.

But when you're the size of a thumbnail,

everything is so much larger.

Even tiny ants are a big deal.

But this turtle comes with its very own suit of armour.

Its arms and legs might be small,

but they are powerful.

Using all its energy,

it instinctively heads towards water.

Out of all the baby turtles that hatch every year,

only 2% will make it to adulthood.

And just when you think you've made it...

..the finish line seems so very far away.

And it's not just the turtles on the move.

BELL RINGS

Now or never.

BELL RINGS

A close shave.

Fortune favours the brave.

Critically endangered in Austria,

every turtle that makes it counts.

At last,

cool and refreshing water.

It might seem unfamiliar to our young turtle,

but, finally, home.

Safety, food,

and even some friends.

Having passed through Germany, Austria and Slovakia,

the Danube is now at the midpoint on its great journey

and arrives in Hungary...

..at the majestic capital of Budapest.

A city that owes its existence to the Danube

and has seen empires rise and fall,

from the Romans to the Crusaders.

In Budapest, art and romance intertwine.

Grand architecture,

and no less than seven bridges,

showcase a place that has been the source

of cultural inspiration down the ages.

Today, with a population of 1.7 million,

it is as important as ever.

Water might be one of the oldest means of transport,

but it's still the cheapest.

And Budapest, because of its unique location,

is key to the Danube's continued success

as the backbone of the European transport network.

Up to 50 million tonnes of freight are transported

along the Danube each year.

Giant cargo ships and barges sail from port to port...

..carrying large and heavy loads,

like cereals, sand, and fuel

that would otherwise have to take less economical routes.

Dockyards act as transport hubs,

where shipping containers and goods are ferried like clockwork.

A giant, moving jigsaw puzzle,

working 24 hours a day,

seven days a week.

It's easy to see the importance of the Danube

to everyday life in Budapest,

but there is more.

A secret, hidden from view.

A shaded pool is hard to spot.

But, for two scientists,

it's an ancient wonder that connects the Danube

to the last Ice Age.

To explore it...

..Dr Gergely Balazs

and Dr Denes Szieberth

need to put on specialised equipment

as they prepare to enter a cave

that is completely filled...

..with freshwater.

The Molnar Janos caves only started to be explored in the 1950s,

with the invention of suitable diving equipment.

GERGELY: We have this busy city on the top of it.

But the cave, it's an ancient thing.

NARRATOR: Crystal clear water,

filtered through rock over millennia,

stretches for almost six kilometres right under Budapest.

And there's more to be discovered with each dive.

DENES: Some of the passages here are huge,

and the water is so clean that you don't even see

that you are in the water.

So you are just flying through these huge spaces.

NARRATOR: The caves offer unique opportunities for the scientists.

DENES: You see things which no-one have seen.

You make measurements which no-one had the opportunity to make.

This is pure exploration.

NARRATOR: Despite the challenges,

the scientists have already begun to unlock

the secrets of these waters...

..concluding that over a million litres of water a day

flows imperceptibly through the caves.

And, in Budapest, there can only be one destination.

There is an obvious connection.

The cave feeds a lake,

which, through a channel under the Locash bath,

the water of this lake is flowing directly into the Danube.

NARRATOR: A hidden tributary...

..joining the Danube on its great journey downstream.

Here, in Hungary,

the Danube's waters may seem slow and sluggish...

..but they still have the ability

to conjure up moments of wildlife magic.

On one of its middle tributaries...

..there's an animal that produces

one of the most spectacular natural events on Earth.

IN HUNGARIAN:

NARRATOR: Freshwater scientist Dr Bela Kiss

is trying to find some of them.

Bela monitors the population of an insect

that hides underwater for up to three years.

But, to do that...

..he has to dive down over four metres to the riverbed.

BELA IN HUNGARIAN:

NARRATOR: It might not look like much...

IN HUNGARIAN:

NARRATOR: But in a few months, these larvae will transform

themselves to become one of the largest mayflies in the world.

For just a few days in June...

..when the water temperature rises,

they begin to hatch.

First, the males take flight.

BELA IN HUNGARIAN:

NARRATOR: For some...

.life is very short indeed.

Soon, more and more appear from the water.

There's no time to hang around.

They have only three hours to live

and just one purpose...

..to find a female and mate.

The search for newly-hatched females

begins a frenzied mating dance.

The sky soon becomes thick with several million mayflies

all mating in groups.

Once common in many parts of the Danube system,

pollution and habitat-loss

mean this great event is becoming harder to find.

But if you know where to look...

..it's an astonishing super-swarm of life.

IN HUNGARIAN:

NARRATOR: As quickly as it began,

this remarkable event...

..iIs over.

After a three-year wait,

it's a short existence,

but it's a life well-lived.

In just one day, they have flown,

mated and died.

By this stage on its journey,

the Danube has been joined by its major tributaries,

the Drava, the Tisza...

..and the Sava.

Combined, they almost triple its flow.

As it reaches its third and final capital city,

Belgrade, in Serbia.

Averaging a kilometre wide,

discharging 5.5 million litres per second.

This now mighty river...

..flows on towards the border with Romania

and one of the last great landmarks on its epic journey.

The Iron Gate gorge.

144 kilometres long, yet narrowing to just 150 metres wide.

For thousands of years,

all traffic on the river had to pass this daunting gateway.

The narrow gorge, with towering cliffs,

was infamous for its dangerous rapids and whirlpools...

..making passage in a boat extremely treacherous.

But in the 1970s,

this part of the Danube was changed forever...

..when engineers harnessed the river's power

and created the Iron Gates Dam...

..one of the largest hydroelectric plants in Europe.

This giant feat of engineering

produces five and a half million megawatts of electricity,

relied upon by 25 million people in Romania and Serbia.

A super-structure that has had an impact on both people...

..and the river.

Below the dam,

the Danube enters the lowlands of Romania and Bulgaria.

In these waters, there is one group of animals

that has been deeply affected by the man-made barrier upstream.

A true monster of the deep...

..the sturgeon.

Some species of sturgeon, such as the Beluga,

live for over 100 years and grow up to six metres long,

the size of a shark.

But it's their eggs that have made them famous,

sold as luxury caviar,

and shipped around the world.

As one of the major rivers draining into the Black Sea,

the Danube is a vital spawning ground for sturgeon.

But overfishing, pollution and the construction of dams,

which have blocked them from their spawning grounds upstream,

mean this river giant has all but disappeared.

Now, sturgeon are thought to be more critically endangered

than any other group of species...

..on the planet.

For one person, their future is something worth fighting for.

It's my passion.

I want to do it all the time.

NARRATOR: Borislava Margaritova,

a fish biologist working in Bulgaria,

is trying to conserve the health of the Danube and its fish,

especially four species of extremely rare sturgeon still found here.

BORISLAVA: The Danube is the last river

in Europe that they spawn naturally.

So we try to protect them because they're very rare now.

NARRATOR: Today, she's going out with her team to survey the river.

BORISLAVA: We are on the river at five in the morning

and we work most of the time until the evening time,

ten in the evening.

It depends what we catch.

NARRATOR: Using nets, they hope to find some fish for their research.

But in such a large river,

and with a small team,

it's not going to be easy.

In nine years of doing this work,

Borislava and her team have only ever caught six sturgeon.

It's very difficult.

You spend eight, nine hours on the river, on the boat,

and you pick up the nets,

and you see the empty nets.

It's very frustrating for me.

NARRATOR: But there is always hope.

And today is a very special day indeed.

Yes!

HE SHOUTS

THEY CHEER

NARRATOR: Incredibly, the team catch not just one sturgeon, but two.

Smaller than the famous Beluga, but no less precious.

A young sterlet sturgeon,

estimated to be between three and five years old.

And a starry sturgeon,

between five and seven years old.

Woo!

NARRATOR: It's a huge result for the team.

We try to catch these specimens for months,

so it's very rare.

We are lucky. - Ah-ha!

BORISLAVA: It's like when somebody have a birthday

and you have this present that you want for many,

many years...

HE CHEERS

..and you have it, and it's not only one, you have both.

NARRATOR: They use their precious time with the fish

to record important data...

..including size and weight.

And carefully attach tags,

so they can monitor the fish's movements.

The significance of this unique encounter is not lost on Borislava.

The sturgeons are like a flagship on the Danube.

So, if the sturgeon are still here,

we will know that the river is healthy.

NARRATOR: There is a way to go.

But, for now, Borislava can celebrate this small victory.

BORISLAVA: Bye, baby.

NARRATOR: It's hoped that conservation efforts,

like restocking and protecting migration routes,

might just give these iconic fish a future.

The Danube has finally arrived

at the last stage of its epic journey,

saving the greatest transformation till last.

The Danube Delta.

Passing through Romania and Ukraine,

this mighty river finally breaks free.

At over 5,000 square kilometres,

this is the largest undisturbed wetland in Europe.

Only fully accessible by boat.

Narrow channels pass through riverine forests

of willow and poplar.

Opening out into freshwater marshes...

..fringed with reedbeds...

..and vast lakes covered in water lilies.

One of Europe's least inhabited places...

..giving space for wildlife to thrive.

More than 5,000 animal and plant species are found here.

The Delta is a globally important destination for birds,

some migrating from as far away as Africa and Asia to breed,

like whiskered terns and squacco herons.

And one bird...

..that has made the Danube Delta its own.

The Great White Pelican.

With 17,000 breeding pairs...

..this is the largest colony in the world

outside of Africa, and their numbers are increasing.

For just a few months,

they'll nest here and feed on the Delta's bounty...

..working together in giant flotillas to feast on fish.

A glorious spectacle at the end of the Danube's great journey,

before, once more, they head into the Black Sea and beyond.

The Danube's waters have flowed through more countries

than any river on Earth...

..through a continent separated by borders

and changed by humanity.

Despite these challenges,

always finding a way to keep going...

..to inspire...

..to nourish...

..and even astonish.

One continent connected and united...

..by water.

The Danube and its tributaries cover 19 countries,

creating the most international river system on Earth.

To capture its secret hidden worlds,

Earth's Great Rivers teamed up with local crews,

contributors and experts right across Europe...

..the people who know the Danube best.

But it was in Slovenia

that they met one person who revealed

a different side to the Danube story...

..a threat that could affect its future,

as well as many other rivers around the world.

Biologist and former Olympic rower -

Rok Rozman.

ROK: It's this mighty river that I call home.

The meaning of it is just extremely big in every way.

NARRATOR: Rok has lived all his life on the Sava river,

one of the Danube's major tributaries...

..and he knows it as well as anyone.

ROK: Sava is really special

because it brings everything that's stored high up

in the mountains down to the bottom of the valley.

Without Sava, this valley wouldn't be green

and we wouldn't have pastures,

and we wouldn't have tourism.

We wouldn't be kayaking,

we wouldn't be fishing,

we wouldn't be enjoying the sound of the river.

It's basically the essence of this place.

Woo-hoo-hoo!

NARRATOR: But it isn't just Rok who takes advantage of the power of rivers.

Over the years,

engineers have harnessed them across Europe

as a source of energy...

..building dams -

a valuable and low carbon source of electricity...

..and a way to store water and help control flooding.

But dams will always create winners and losers.

And these barriers have complex implications...

..dramatically reshaping the river's ecology

up and downstream...

WHISTLE TOOTS

..which is a concern

for many who live alongside these rivers.

The Sava river already has over ten dams

and there are plans for ten more.

For Rok,

the damage caused by these barriers to the wildlife

and ecology of the river is too great to ignore.

ROK: It would be sad to see

such destruction to this river, you know?

The river provides home for these animals.

You know, they can't go anywhere else.

If a bird lives on a gravel bar, well,

then it lives on a gravel bar.

If an otter needs a river with fish, well,

then that's what this river provides,

and that's why it's so important to protect these rivers.

And by the time we realise

the negative effects, it's already way too late.

And it just...

..breaks my heart and mind. Erm...

Because if these plans go ahead,

the place where I'm sitting right now will be underwater.

And it's not just me, I'm the last in line, you know?

My enjoyment in kayaking is the last in line.

There's fields here, people depend on these fields.

There's an otter family living there.

Where will the birds go? Where will the plants go?

NARRATOR: Free-flowing rivers can be hard to find in Europe.

Recent research has suggested more than a million barriers

fragment the continent's rivers.

The Danube and its tributaries

have seen more than 700 dams

and weirs built along their course.

The effect of these man-made structures

on wildlife is significant.

Faced with this, Rok decided to do something.

ROK: I realised that emotion without action

is basically going to ruin your soul eventually,

and I called a bunch of my friends and I said,

"Look, guys, these rivers are going to be destroyed

"without anybody knowing if we don't do something."

CHEERING

We realised that the core of the problem is that

there's not enough people spending time next to the river

and we said, "Well, we're going to take people rafting.

"We're going to take people picnicking by the river.

"We're going to take them kayaking, swimming, whatever."

You first need to know a place

to fall in love a place

and only then you're going to feel the need to protect it.

NARRATOR: Rok's initiative has already helped stop

the building of 12 new dams in the region.

And one of the dams on his home river,

the Sava, has now been delayed.

But it's also focused attention

on the importance of allowing rivers to flow naturally.

Along with lakes and wetlands,

rivers cover less than 1% of the planet...

..and yet are home to a quarter of all vertebrate species...

..including over half of all species of fish.

ROK: Hydro is seen as a renewable source.

Their intentions might be good,

but the reality is that what we're doing is, basically,

we're destroying the most important parts of our environment.

NARRATOR: Hydropower is a major low-carbon source of electricity,

but as decision makers are coming to understand

the value of free-flowing rivers...

..its use is being reassessed.

And a revolution in renewable technologies

may offer exciting alternatives...

..like solar...

..wind, and battery storage,

which could all help keep rivers flowing.

My hope for the future is that people realise

the importance of rivers for themselves...

..then also for all the wildlife and plants,

and whatever lives next to it...

..because the time is running out.