DAVID ATTENBOROUGH: The power of the sun drives the seasons,
transforming our planet.
Vast movements of ocean and air currents
bring dramatic change throughout the year.
And in a few special places, these seasonal changes
create some of the greatest wildlife spectacles on Earth.
One of the most remarkable transformations
occurs here in Southern Africa, in the desert lands of the Kalahari.
Large herds of animals trek for months in search of food and water,
waiting for an event that will dramatically change their lives.
For once a year, life-giving water turns an area of unforgiving desert
into a vast, watery paradise known as the Okavango.
Where and when the Okavango will flood
determines the fate of millions of animals,
making this one of nature's truly great events.
In the heart of Southern Africa, the desert lands of the Kalahari
cover an area of almost 400,000 square miles.
It's one of driest places on Earth,
yet miraculously, great herds of grazing animals survive here.
They lead a nomadic existence,
trekking huge distances in search of food and water.
It's the start of the dry season. It won't rain for eight months,
and so life, already hard, is about to get even harder.
Of all the animals here,
perhaps the most resourceful are the elephants.
Each family is led by an older female, the matriarch,
and they all rely on her experience to guide them through the desert.
Her years here have taught this matriarch that, one day,
hundreds of miles to the west, she will find a lush grassland.
But before she will find it,
her family will have to survive many months in the desert.
The water that could transform their lives
has its origins a thousand miles away,
in the rain clouds over the highlands of Angola.
(THUNDER CRASHES)
The rain is so plentiful it has the power to transform a desert.
It cascades southwards, not to the sea, but into the heart of the Kalahari,
towards a basin shaped like a hand
known as the Okavango.
Here it will fill the swamp that lies at its entrance.
And only if the rains have been plentiful
will water flood out onto the arid plains beyond,
transforming them into the grassland paradise
that the herds so badly need.
Out in the desert, the elephants need to find water every three days.
Thirsty elephants often race into pools,
but the matriarch knows that her family must not rush in.
This pool is stagnant,
and the elephants have a trick that deals with that.
Sediment settles to the bottom,
and the cleaner, fresher water lies on the surface.
They skim it carefully from the top.
Then, as gently as elephants can, they move forward slowly,
trying not to disturb the stagnant layers.
But precious water like this draws in herds from far and wide.
In the exuberance of a greeting all their careful work is undone.
When bulls are forced together by the need for water,
tempers can flare.
At this time of year, food and water can often be far apart.
And so, now that the little ones are refreshed,
the family has to head off to find food.
The distant Okavango plains that they're heading for are still dry,
and getting even drier.
Trapped catfish struggle in a shrinking pool.
And the burning sun is not their only enemy.
(CAWING)
An opportunity like this attracts eagles from many miles away.
Usually, they dive and snatch fish from the surface of the water,
but in this drought they won't have to work so hard.
These are prized catches.
Marabou storks and jackals muscle in on the leftovers.
But even with this bounty of fish,
it's in an eagle's nature to steal a meal rather than catch its own.
And all this squabbling gives the marabou a chance.
Got it!
Only the return of the flood can save these fish now.
All around these pools,
the grass on the Okavango plains continues to wither and die.
But there's still some nourishment left in the leaves,
and millions of tiny mouths make the most of what remains.
Termites chop the dead grass and drag it underground
to feed their colony.
They play a crucial role,
helping to return nutrients to these poor soils.
But now, taking the last, precious grass,
they leave dust and sand in its place.
With the grazing animals dispersed far and wide,
it's leaner times for predators here.
Only a desperate leopard would tackle a porcupine.
This youngster is about to meet double trouble.
The only place to get a bite is on their undersides.
But the porcupines work together to watch each others' backs.
The leopard will have to flip one over.
Pin-sharp quills can easily snap off and become embedded in flesh.
It's a highly effective defence that can also be turned into attack.
It's a harsh lesson,
but with luck and a bit of healing time, there'll be no lasting damage.
Two hundred miles away,
the pulse of life-giving water has now reached the swampland
at the entrance to the Okavango.
Here, thick beds of papyrus act like a sponge,
slowing the water's progress.
The swamp can take months to fill,
and only then, if there is enough water,
can it overflow and rejuvenate the plains on which the herds depend.
Far to the east,
the matriarch elephants have led their families to desert woodlands.
It seems an odd place to come - there's no sign of food
and there's little shade for the calves.
But elephants can do something unusual.
They can eat and digest seemingly lifeless branches.
The youngsters need to learn that dry sticks are nutritious,
and that there is moisture in the bark.
But bark won't feed the youngest calves.
They need to drink 1 5 litres of milk a day,
so their mothers desperately need water as well as food.
Exhaustion has got the better of one young female.
But she won't get the chance to rest for long.
The next waterhole could be 30 miles away,
and the whole herd needs to get moving.
Back on the Okavango plains,
the last remnants of grass are going up in smoke.
It's bad news for the few grazers that remain.
A few birds collect the escaping insects.
But fires don't help those who need to eat grass here and now.
The Okavango plains are at their most desolate.
Yet, out in the desert,
the elephant herds are heading towards them.
The matriarchs guide their families along the maze of trails
to the next waterhole.
And this time there's no hanging about.
It soon turns into a mud bath.
But elephants have a use for the mud, too,
for mud acts both as a sunscreen and an insect repellent.
Buffalo have learned to follow the elephant trails to water.
There is a clear pecking order here.
Elephants take priority,
and zebra are the last in the line.
(SNUFFLING)
Even when young bulls have drunk their fill,
they still torment the buffalo.
And they definitely know which end to aim for.
By the time the herds face their final trek across open desert,
the swamp has filled.
The channels which lead out onto the parched plains
get their first, welcome trickle of water.
Amazingly, when the plains are at their driest,
fresh water from a distant land spills into the parched river beds.
First it fills the dry channels,
leaving the baked plains on either side hard and dry.
All along the route it finds empty pools to fill.
And now, these pools become magnets for birds,
which flock here from the surrounding desert lands.
Red-billed quelea can now collect those grass seeds
that the termites have missed.
For most of the year, the quelea are nomadic,
and it's this freedom to follow the water
that helps make quelea one of the most numerous birds on Earth.
As the water fills the Okavango,
animals that have survived in shrinking waterholes
begin to move in.
Female hippos gather in the best territories.
And this male is prepared to fight for one.
Only a dominant bull will mate with the females,
and the current chieftain isn't prepared to give way.
(GRUNTS)
The intimidation begins.
When neither backs down, there can be only one outcome.
Fights can go on for hours and can be to the death.
Forward-pointing tusks can stab right through protective blubber.
This savage bite to the head brings the contest to an end.
The incumbent has re-established his right to mate with the females,
and he wastes no time.
This is a prime territory,
and he will face many more challenges if he is to continue to hold it.
The loser is badly injured.
Hippos can die from infected wounds,
but this young male is fit and should survive.
Ox-peckers are a mixed blessing.
They keep his wounds clean, but they also keep them open.
Fresh water continues to pump through the Okavango plains,
bringing life wherever it flows.
But out in the Kalahari, water is now almost impossible to find.
A matriarch has led her family many miles,
only to find the waterhole empty.
This year the drought is gripping hard.
Each matriarch encourages her family onward.
The calves' lives depend on her.
And with pools so scarce now,
even when she finds water, they won't be drinking alone.
At this time of year, some lion prides base themselves around waterholes,
and they're always on the lookout for a meal.
But the elephants' desperate need to drink outweighs the risk.
The mothers are producing less milk, and the calves are weak.
The adults try to shield them from watchful eyes.
It's an uneasy stand-off.
In daylight, the elephants should have nothing to fear.
The lions creep as close as they dare, as they too try to drink.
One mistake from an elephant and the lions could attack.
Big cats keep tired elephants on their toes.
(TRUMPETING)
While the desert experiences the peak of the drought,
the meandering network of channels in the Okavango
is finally brimful.
They are ready to overflow.
Fish gather, ready to ride the flood as a miracle begins to materialise.
And the barrier of desert sand seems to dissolve in the magical water.
Under cloudless Kalahari skies,
fresh, sweet water at last begins to bathe the parched plains.
Millions upon millions of litres surge over the banks.
This is what the fish have been waiting for.
New life returns.
And as the water soaks deep into the sand,
it stirs dormant animals into life.
Others are more forcibly evicted.
It's all fresh food, a banquet ready for the feasting.
Water birds follow the advancing front, making the most of the sudden harvest.
The plains soon teem with life.
But not all are here to feed.
Some have come to breed.
No one knows where they've come from,
but within moments of the flood's arrival,
tens of thousands of dragonflies appear at the water's edge.
The vivid red male leads his partner in a magical dance,
guiding her to lay their eggs in the shallows.
The flood spills ever onwards,
until it finally reaches the outer fringes of the Okavango.
The catfish, miraculously, still cling to life.
Within moments, the life-giving power of fresh water revitalises them.
And now, on the plains that appeared so lifeless,
some of the most beautiful and colourful changes occur.
Within days, fields of lilies burst into life.
They provide pollen for the early bees, and a hiding place for reed frogs.
And it's only now that the most crucial gift of the flood, the grass
that the desert herds need so badly, begins to grow.
Hippos bulldoze their way towards the sprouting grasslands,
their paths opening up new arteries that help keep the water flowing.
In just a few weeks,
thousands of square miles of dry desert plains
are turned into a watery green grassland.
The network of hippo paths benefits all kinds of other animals,
from predatory crocodiles to the grazing herds.
This fresh grass is what the elephants, and indeed all the grazing animals,
have been waiting for.
Their pace quickens.
For months, they have only known the dry smell of the desert.
And now, they can catch the scent of fresh grass in the wind.
Red lechwe are the first to take advantage of the young shoots.
The lions are no threat here.
They're not very fast in water, and their prey seem to know it.
Lechwe revel in the safety the flood brings.
Soon they will be joined by the herds of elephant and buffalo.
And the lions seem to know they're not far away.
Baboons don't enjoy getting their feet wet,
but the banquet of flowers and juicy snails is just irresistible.
But they are at their most vulnerable here
from lurking crocodiles,
so they keep an ever-watchful eye.
Babies just cling on tight and hope the water doesn't get too deep.
At their feet, the flooded plains are now a vast fish nursery,
teeming with life.
Predatory fish follow.
But they too will have to be wary.
For the Okavango now puts on one of the finest bird shows
to be seen anywhere in the world.
The rising waters create thousands of tiny islands.
Safe from predators, surrounded by fish,
these are the perfect place to raise chicks.
This is the miracle of the Okavango.
Once a year, it provides a magical time of plenty
at the height of the dry season, in the middle of a desert.
Only now, with the grasslands at their most productive,
do the great herds arrive,
and they've timed it to perfection.
The herds grow larger as elephant families and buffalo
converge from all over the desert.
But as they all get closer to the flooded grassland,
there is one final challenge to face.
Lions have chosen this thick cover to lay their ambushes.
Their favourite prey is the buffalo.
Adult buffalo are powerful and can easily trample lions,
so the lionesses seek out weaker calves that fall behind the herd.
A nervous buffalo mother spots their approach
and the herd stampedes.
One lioness takes a gamble, moving in on a well-protected calf.
The buffalo close ranks,
and suddenly, the lionesses beat a hasty retreat.
(ROARING)
In the panic, calves are separated from their mothers.
Amid the confusion, a lioness darts in and grabs one.
Many buffalo will fall to lions here.
Lions are opportunists,
and even an unguarded elephant calf can be vulnerable.
The elephants are nervous.
The scent of lion is all around, yet they can't see them.
A lioness is following them,
trying to separate the young straggler from the herd.
(TRUMPETING)
One adolescent fights back, confronting its enemy.
In a panic, the family stampedes.
The straggler is taken.
After months of arduous trekking,
this elephant family has lost one of its young ones.
But most of the elephants, at last, have made it through,
and the great flood awaits.
Older elephants have been here many times before,
but the newest calves have never seen so much refreshment.
At last, they get that first drink of sweet, fresh water.
Thousands of buffalo and zebra
have also made it to the magical Okavango wetlands.
Somehow, these remarkable elephants have learned how to find a flood
from hundreds of miles away, and to time their arrival just right.
If it wasn't for this annual gift of precious grass,
the herds couldn't survive the dry season
in the surrounding Kalahari.
This year the Great Flood has lived up to its name.
The lives of these elephants
are dominated by this annual rhythm of wet and dry,
a seasonal cycle driven by the power of the sun.
The Okavango River has no great lake to flow into,
nor does it ever reach the sea.
Its life-giving waters simply evaporate
into the great emptiness of the Kalahari sky.
In a few months, some may fall as rain far to the north,
and, once again,
become part of this miraculous event in the Okavango,
that is the Great Flood.
In the making of ''The Great Flood'',
the biggest challenge for the filming team
was to capture the magical moment
when new floodwater first transformed the desert.
But to do this would mean crossing
some of the most challenging terrain in the world,
pitting themselves against the very water they'd come to film.
We're right in the heart of the delta right now.
The flood's been in here for a couple of weeks,
but the real action's happening out west,
across 20 kilometres of deep swampland.
And our mission right now is to get this crane rig out there
to where the action's really happening,
and see if we can get a great new perspective on the flood coming in.
ATTENBOROUGH: To achieve this new look,
the team were using some of the latest camera technology.
But first they had to find the advancing flood,
and the only way to do this was from the air.
Mike has worked here for more than 20 years,
and knows that this will be a race against time.
The flood was already well advanced,
and wasn't going to wait for a film crew.
Mike pinpointed the water's edge,
and on his way back, laid a GPS trail to follow.
The flight took only 20 minutes,
but it would take the ground crew at least three days or more
to get there.
And there was no guarantee they'd get through the swamps.
-Are you watching for crocodiles? -Yeah.
Okay, good.
ATTENBOROUGH: Fortunately, at this cooler time of year,
crocodiles are less active and wouldn't pose a serious threat.
The reason Richard's wading in crocodile-infested waters
is that we're on this side, and we need to be on the other side,
and he's wading so that we can see how deep it is
for this vehicle to cross.
ATTENBOROUGH: These trucks are specially adapted
to cope with such extreme conditions.
They can drive in water up to seven feet deep,
and cross all but the boggiest terrain.
Unfortunately, not all the equipment fared so well.
I don't think this is gonna be much use to anyone.
ATTENBOROUGH: But even the vehicles weren't immune to such punishing use.
Problems always arise when you least expect it.
This truck, which is our swamp truck,
has decided
to give us problems again.
The dif has basically collapsed on us.
We're running out of daylight at the moment,
so we got to swap this out.
ATTENBOROUGH: To film here, you have to be a jack of all trades,
a filmmaker, a tracker and a mechanic.
Despite some on-the-spot bush repairs, a replacement part had to be ordered in.
Hello.
(GROANS)
It's going to be a long night in the bush.
ATTENBOROUGH: All the crew could do now was wait.
With the nearest garage over two days away by truck,
there was only one way the new part could be delivered.
Now the crew could get back on the road and start making up for lost time.
-Are you all right? -MAN: Yeah, I'm good.
ATTENBOROUGH: But they would have to choose their route carefully.
The best way to pick a path is where the elephants cross,
because they've got regular routes that are the shallowest places.
But often where they've crossed, it's churned up the mud as well,
so we try and stay slightly off to the edge of the path.
But once you get into the middle of that,
it's just hope like hell and keep going.
Because it's probably deep and very soggy in the middle.
Okay, this is getting a bit silly. We're officially stuck.
ATTENBOROUGH: Mike's concerns proved well-founded.
The shallower route was simply too boggy.
That left the crew with no choice but to tackle the longer, deeper route,
and hold their nerve.
MAN: It's coming over your windows.
(EXCLAIMS) I'm getting wet.
(EXCLAIMS) Water's coming in!
It's a little damp in here now.
That was interesting, but we made it across the swamp!
ATTENBOROUGH: Success!
Mike and the team had finally got ahead of the flood.
They were now in a truly privileged position,
ready to capture the amazing transformation
that was about to unfold.
Okay, so drop the camera over the middle of the pool there.
The flood had arrived.
Here it comes.
Three, two, one...
ATTENBOROUGH: Using cranes and specially developed close-up camera systems,
the Nature's Great Events team could finally set about
bringing the advancing flood to life.
This is one of those magical transformation moments,
where you've got a landscape which is asleep that way,
and you've got the flood, which is like the catalyst
which is going to bring the landscape to life.
And it's happening right in front of us, which is amazing.
And we've got a bit of macro kit
that exists nowhere else in the world,
and we're able to just follow it at the really tiniest level.
ATTENBOROUGH: This was the Great Flood,
but filmed on a scale that had never been seen before.
Seems like my hole is filling up.
I'm going to get wet, Rick. I'm going to drown in three inches of water.
ATTENBOROUGH: Each year, the magical flood rewards Mike with something new.
Despite years of filming here, he'd never seen so many dragonflies.
It's amazing, that, isn't it?
Have you ever watched this happen before?
It is amazing.
I mean, you think this is going on all over the delta.
Miles and miles and miles of water just spreading everywhere
at this rate.
Incredible.
ATTENBOROUGH: And the team had managed to capture
just a tiny part of it,
revealing in intimate detail the character of the Great Flood.