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00:00The power of the sun drives the seasons, transforming our planet.
00:13Vast movements of ocean and air currents bring dramatic change throughout the year.
00:23And in a few special places, these seasonal changes create some of the greatest wildlife
00:29spectacles on earth.
00:34One of the most remarkable transformations occurs here in southern Africa, in the desert
00:40lands of the Kalahari.
00:44Large herds of animals trek for months in search of food and water, waiting for an event
00:50that will dramatically change their lives.
00:54For once a year, life-giving water turns an area of unforgiving desert into a vast watery
01:02paradise known as the Okavango.
01:19Where and when the Okavango will flood determines the fate of millions of animals, making this
01:27one of nature's truly great events.
01:55In the heart of southern Africa, the desert lands of the Kalahari cover an area of almost
02:01400,000 square miles.
02:06It's one of the driest places on earth, yet miraculously, great herds of grazing animals
02:12survive here.
02:17They lead a nomadic existence, trekking huge distances in search of food and water.
02:35It's the start of the dry season.
02:37It won't rain for eight months, and so life, already hard, is about to get even harder.
02:56Of all the animals here, perhaps the most resourceful are the elephants.
03:05Each family is led by an older female, the matriarch, and they all rely on her experience
03:11to guide them through the desert.
03:16Her years here have taught this matriarch that one day, hundreds of miles to the west,
03:27she will find a lush grassland.
03:32But before she will find it, her family will have to survive many months in the desert.
03:41The water that could transform their lives has its origins a thousand miles away, in
03:47the rain clouds over the highlands of Angola.
04:05The rain is so plentiful, it has the power to transform a desert.
04:13It cascades southwards, not to the sea, but into the heart of the Kalahai, towards a basin
04:20shaped like a hand, known as the Okavango.
04:30Here it will fill the swamp that lies at its entrance.
04:35And only if the rains have been plentiful will water flood out onto the arid plains
04:40beyond, transforming them into the grassland paradise that the herds so badly need.
04:55Out in the desert, the elephants need to find water every three days.
05:02Thirsty elephants often race into pools, but the matriarch knows that her family must not
05:08rush in.
05:15This pool is stagnant, and the elephants have a trick that deals with that.
05:25Sediment settles to the bottom, and the cleaner, fresher water lies on the surface.
05:35They skim it carefully from the top.
05:50Then, as gently as elephants can, they move forward slowly, trying not to disturb the
05:56stagnant layers.
06:17Precious water like this draws in herds from far and wide.
06:29In the exuberance of a greeting, all their careful work is undone.
06:44When bulls are forced together by the need for water, tempers can flare.
07:14At this time of year, food and water can often be far apart.
07:32And so, now that the little ones are refreshed, the family has to head off to find food.
07:50The distant Okavango plains that they're heading for are still dry, and getting even drier.
08:04Trapped catfish struggle in the shrinking pool.
08:21And the burning sun is not their only enemy.
08:31An opportunity like this attracts eagles from many miles away.
08:40Usually they dive and snatch fish from the surface of the water, but in this drought,
08:45they won't have to work so hard.
08:53These are prized catches.
09:05Marabou storks and jackals muscle in on the leftovers.
09:14But even with this bounty of fish, it's in an eagle's nature to steal a meal rather than
09:20catch its own.
09:51And all this squabbling gives the marabou a chance.
10:04Got it.
10:09Only the return of the flood can save these fish now.
10:15All around these pools, the grass on the Okavango plains continues to wither and die.
10:26But there's still some nourishment left in the leaves, and millions of tiny mouths make
10:32the most of what remains.
10:40The marabou ants chop the dead grass and drag it underground to feed their colony.
10:49They play a crucial role, helping to return nutrients to these poor soils.
10:54But now, taking the last precious grass, they leave dust and sand in its place.
11:09With the grazing animals dispersed far and wide, it's leaner times for predators here.
11:30Only a desperate leopard would tackle a porcupine.
11:40This youngster is about to meet double trouble.
11:47The only place to get a bite is on their undersides.
11:52The porcupines work together to watch each other's backs.
12:08The leopard will have to flip one over.
12:17Thin, sharp quills can easily snap off and become embedded in flesh.
12:38It's a highly effective defence that can also be turned into attack.
12:59It's a harsh lesson, but with luck and a bit of healing time, there'll be no lasting damage.
13:13Two hundred miles away, the pulse of life-giving water has now reached the swampland at the
13:19entrance to the Okavango.
13:22Clear, thick beds of papyrus act like a sponge, slowing the water's progress.
13:29The swamp can take months to fill, and only then, if there is enough water, can it overflow
13:36and rejuvenate the plains on which the herds depend.
13:47Far to the east, the matriarch elephants have led their families to desert woodlands.
13:58It seems an odd place to come.
14:00There's no sign of food, and there's little shade for the calves.
14:09But elephants can do something unusual.
14:16They can eat and digest seemingly lifeless branches.
14:33The youngsters need to learn that dry sticks are nutritious, and that there is moisture
14:41in the bark.
14:46But bark won't feed the youngest calves.
14:49They need to drink three gallons of milk a day, so their mothers desperately need water
14:56as well as food.
15:01Exhaustion has got the better of one young female.
15:11But she won't get the chance to rest for long.
15:14The next waterhole could be 30 miles away, and the whole herd needs to get moving.
15:34Back on the Okavango plains, the last remnants of grass are going up in smoke.
15:47It's bad news for the few grazers that remain.
16:04The few birds collect the escaping insects.
16:13But fires don't help those who need to eat grass here and now.
16:33The Okavango plains are at their most desolate, yet out in the desert, the elephant herds
16:40are heading towards them.
16:50The matriarchs guide their families along the maze of trails to the next waterhole.
17:04This time, there's no hanging about.
17:24It soon turns into a mud bath.
17:30But elephants have a use for the mud, too, for mud acts both as a sunscreen and an insect
17:38repellent.
17:52Buffalo have learned to follow the elephant trails to water.
18:05There is a clear pecking order here.
18:09Elephants take priority.
18:12And zebra are the last in the line.
18:28Even when young bulls have drunk their fill, they still torment the buffalo.
18:36And they definitely know which end to aim for.
18:51By the time the herds face their final trek across open desert, the swamp has filled.
19:01The channels, which lead out onto the parched plains, get their first welcome trickle of
19:06water.
19:11Amazingly, when the plains are at their driest, fresh water from a distant land spills into
19:22the parched riverbeds.
19:27First, it fills the dry channels, leaving the baked plains on either side hard and dry.
19:54Soon along the route, it finds empty pools to fill.
20:01And now, these pools become magnets for birds, which flock here from the surrounding desert
20:07lands.
20:14Bird-billed quealier can now collect those grass seeds that the termites have missed.
20:39For most of the year, the quealier are nomadic.
20:43And it's this freedom to follow the water that helps make quealier one of the most numerous
20:48birds on earth.
21:08As the water fills the Okavango, animals that have survived in shrinking waterholes begin
21:14to move in.
21:18Female hippos gather in the best territories, and this male is prepared to fight for one.
21:34Only a dominant bull will mate with the females, and the current chieftain isn't prepared to
21:40give way.
21:49The intimidation begins.
22:01When neither backs down, there can only be one outcome.
22:20This can go on for hours, and can be to the death.
22:32Three-pointing tusks can stab right through protected blubber.
22:49This
23:14savage bite to the head brings the contest to an end.
23:30The incumbent has re-established his right to mate with the females, and he wastes no
23:37time.
23:43This is a prime territory, and he will face many more challenges if he is to continue
23:49to hold it.
23:58The loser is badly injured.
24:04Hippos can die from infected wounds, but this young male is fit and should survive.
24:16Oxpeckers are a mixed blessing.
24:18They keep his wounds clean, but they also keep them open.
24:35Freshwater continues to pump through the Okavango Plains, bringing life wherever it flows.
24:43But out in the Kalahari, water is now almost impossible to find.
24:55A matriarch has led her family many miles, only to find the waterhole empty.
25:06This year, the drought is gripping hard.
25:13Each matriarch encourages her family onward.
25:18The calves' lives depend on her.
25:27And with pools so scarce now, even when she finds water, they won't be drinking alone.
25:44At this time of year, some lion prides base themselves around waterholes.
25:50And they're always on the lookout for a meal.
26:03But the elephant's desperate need to drink outweighs the risk.
26:13The mothers are producing less milk, and the calves are weak.
26:23The adults try to shield them from watchful eyes.
26:30It's an uneasy standoff.
26:38In daylight, the elephants should have nothing to fear.
26:51The lions creep as close as they dare, as they too try to drink.
27:08One mistake from an elephant, and the lions could attack.
27:16And cats keep tired elephants on their toes.
27:27While the desert experiences the peak of the drought, the meandering network of channels
27:32in the Okavango is finally brimful.
27:37They're ready to overflow.
27:44Fish gather, ready to ride the flood as a miracle begins to materialize.
27:54And the barrier of desert sand seems to dissolve in the magical water.
28:12Under cloudless Kalahari skies, fresh, sweet water at last begins to bathe the parched
28:50Millions upon millions of gallons surge over the banks.
29:08This is what the fish have been waiting for.
29:15New life returns.
29:40And as the water soaks deep into the sand, it stirs dormant animals into life.
29:56Others are more forcibly evicted.
30:03It's all fresh food, a banquet ready for the feasting.
30:19Water birds follow the advancing front, making the most of the sudden harvest.
30:47The plains soon team with life.
30:52But not all are here to feed.
30:55Some have come to breed.
31:03No one knows where they've come from, but within moments of the flood's arrival, tens
31:08of thousands of dragonflies appear at the water's edge.
31:24The vivid red male leads his partner in a magical dance, guiding her to lay their eggs
31:30in the shallows.
31:59The flood spills ever onwards until it finally reaches the outer fringes of the Okavango.
32:24The catfish miraculously still cling to life.
32:50In moments, the life-giving power of fresh water revitalizes them.
33:20And now, on the plains that appeared so lifeless, some of the most beautiful and colorful changes
33:34occur.
33:39In days, fields of lilies burst into life.
33:54They provide pollen for the early bees and a hiding place for reed frogs.
34:12And it's only now that the most crucial gift of the flood, the grass that the desert herds
34:17need so badly, begins to grow.
34:48Hippos bulldoze their way towards the sprouting grasslands, their paths opening up new arteries
34:55that help keep the water flowing.
35:06In just a few weeks, thousands of square miles of dry desert plains are turned into a watery,
35:13green grassland.
35:19The network of hippo paths benefits all kinds of other animals, from predatory crocodiles
35:26to the grazing herds.
35:46This fresh grass is what the elephants, and indeed all the grazing animals, have been
35:51waiting for.
36:01Their pace quickens.
36:03For months, they have only known the dry smell of the desert.
36:10And now they can catch the scent of fresh grass in the wind.
36:19And lechwe are the first to take advantage of the young shoots.
36:49The lions are no threat here.
37:16They're not very fast in water, and their prey seem to know it.
37:24Lechwe revel in the safety the flood brings.
37:46Soon, they will be joined by the herds of elephant and buffalo.
38:15And the lions seem to know they're not far away.
38:29Baboons don't enjoy getting their feet wet, but the banquet of flowers and juicy snails
38:37is just irresistible.
38:56But they are at their most vulnerable here, from lurking crocodiles, so they keep an ever-watchful
39:03eye.
39:06Others just cling on tight and hope the water doesn't get too deep.
39:13At their feet, the flooded plains are now a vast fish nursery, teeming with life.
39:28Every fish follow, but they, too, will have to be wary, for the okavango now puts on one
39:46of the finest bird shows to be seen anywhere in the world.
40:13The rising waters create thousands of tiny islands.
40:18Safe from predators, surrounded by fish, these are the perfect place to raise chicks.
40:34This is the miracle of the okavango.
40:41Once a year, it provides a magical time of plenty at the height of the dry season, in
40:46the middle of a desert.
40:59Only now, with the grasslands at their most productive, do the great herds arrive, and
41:05they've timed it to perfection.
41:11The herds grow larger as elephant families and buffalo converge from all over the desert.
41:24But as they all get closer to the flooded grassland, there is one final challenge to
41:30face.
41:49Lions have chosen this thick cover to lay their ambushes.
42:00Their favorite prey is the buffalo.
42:08Adult buffalo are powerful and can easily trample lions, so the lionesses seek out weaker
42:17calves that fall behind the herd.
42:28A nervous buffalo mother spots their approach, and the herd stampedes.
42:37One lioness takes a gamble, moving in on a well-protected calf.
42:45The buffalo close ranks, and suddenly the lionesses beat a hasty retreat.
43:07In the panic, calves are separated from their mothers.
43:13Amid the confusion, a lioness darts in and grabs one.
43:25Many buffalo will fall to lions here.
43:36Lions are opportunists, and even an unguarded elephant calf can be vulnerable.
43:54The elephants are nervous.
44:00The scent of lion is all around, yet they can't see them.
44:08The lioness is following them, trying to separate the young straggler from the herd.
44:17One adolescent fights back, confronting its enemy.
44:36In the panic, the family stampedes.
44:41The straggler is taken.
44:58After months of arduous trekking, this elephant family has lost one of its young ones.
45:08But most of the elephants, at last, have made it through, and the great flood awaits.
45:22Older elephants have been here many times before, but the newest calves have never seen
45:27so much refreshment.
45:47At last, they get that first drink of sweet, fresh water.
46:17Thousands of buffalo and zebra have also made it to the magical Okavango wetlands.
46:46Somehow, these remarkable elephants have learned how to find a flood from hundreds of miles
46:53away and to time their arrival just right.
47:02If it wasn't for this annual gift of precious grass, the herds couldn't survive the dry
47:08season in the surrounding Kalahari.
47:17This year, the great flood has lived up to its name.
47:42The lives of these elephants are dominated by this annual rhythm of wet and dry, a seasonal
47:49cycle driven by the power of the sun.
48:02The Okavango River has no great lake to flow into, nor does it ever reach the sea.
48:10Its life-giving waters simply evaporate into the great emptiness of the Kalahari sky.
48:21In a few months, sun may fall as rain far to the north and, once again, become part
48:28of this miraculous event in the Okavango that is the great flood.
48:58In the making of the great flood, the biggest challenge for the filming team was to capture
49:07the magical moment when new flood water first transformed the desert.
49:13But to do this would mean crossing some of the most challenging terrain in the world,
49:22pitting themselves against the very water they'd come to film.
49:33We're right in the heart of the delta right now.
49:36Flood's been in here for a couple of weeks, but the real action's happening out west across
49:4020 kilometers of deep swamp land.
49:44And our mission right now is to get this crane rig out there to where the action's really
49:48happening and so you can get a great new perspective on the flood coming in.
49:54To achieve this new look, the team were using some of the latest camera technology, but
50:00first they had to find the advancing flood.
50:05And the only way to do this was from the air.
50:13Mike has worked here for more than 20 years and knows that this will be a race against
50:18time.
50:22The flood was already well-advanced and wasn't going to wait for a film crew.
50:34Mike pinpointed the water's edge and on his way back laid a GPS trail to follow.
50:45The flight took only 20 minutes, but it would take the ground crew at least three days or
50:50more to get there.
50:54And there was no guarantee they'd get through the swamps.
51:01Are you watching for crocodile?
51:02Yeah.
51:03Okay, good.
51:04Fortunately, at this cooler time of year, crocodiles are less active and wouldn't pose
51:14a serious threat.
51:16The reason Richard's wading in crocodile-infested waters is that we're on this side and we need
51:21to be on the other side.
51:23And he's wading so that we can see how deep it is for this vehicle to cross.
51:32These trucks are specially adapted to cope with such extreme conditions.
51:39They can drive in water up to seven feet deep.
51:46And cross all but the boggiest terrain.
51:51Unfortunately, not all the equipment fared so well.
51:58I don't think this is going to be much use to anyone.
52:03But even the vehicles weren't immune to such punishing use.
52:09Problems always arise when you least expect it.
52:14Kubu, this truck, is our swamp truck, has decided to give us problems again.
52:26The diff has basically collapsed on us.
52:27We're running out of daylight at the moment, so we've got to sort this out.
52:36To film here, you have to be a jack-of-all-trades, a filmmaker, a tracker and a mechanic.
52:46Despite some on-the-spot bush repairs, a replacement part had to be ordered in.
52:51Hello.
52:52Hello.
52:53It's going to be a long night in the bush.
53:03All the crew could do now was wait.
53:13With the nearest garage over two days away by truck, there was only one way the new part
53:18could be delivered.
53:29Now the crew could get back on the road and start making up for lost time.
53:35Yeah, I'm good.
53:40But they would have to choose their route carefully.
53:44The best way to pick a path is where the elephants cross, because they, you know, they've got
53:49regular routes that are the shallowest places.
53:52But often where they've crossed, it's churned up the mud as well, so we try and stay slightly
53:55off the other path.
53:56But once you get into the middle of that, it's just hope like hell and keep going, because
54:01you know, it's probably deep and very soggy in the middle.
54:21Mike's concerns proved well-founded.
54:24The shallower route was simply too boggy.
54:30That left the crew with no choice but to tackle the longer, deeper route and hold their
54:35nerve.
55:06It's a little damp in here now, right?
55:29That was interesting, but we made it.
55:47Success.
55:48Mike and the team had finally got ahead of the flood.
55:56They were now in a truly privileged position, ready to capture the amazing transformation
56:03that was about to unfold.
56:05OK, so drop the camera over the middle of the pool there.
56:14The flood had arrived.
56:18Here it comes.
56:44Using cranes and specially developed close-up camera systems, the Nature's Great Events
56:50team could finally set about bringing the advancing flood to life.
56:54This is one of those magical transformation moments where you've got a landscape which
57:00is asleep that way, and you've got the flood, which is like the catalyst, which is going
57:04to bring that landscape to life, and it's happening right in front of us, which is amazing.
57:10We've got a bit of macro kit that exists nowhere else in the world, and we're able
57:16to just follow it at the really tiniest level.
57:31This was the Great Flood, but filmed on a scale that had never been seen before.
57:37Seems like my hole's filling up.
57:53I'm going to get wet, Rick.
57:56I'm going to drown in three inches of water.
58:04Each year, the magical flood rewards Mike with something new.
58:09Despite years of filming here, he had never seen so many dragonflies.
58:19It's amazing, though, isn't it?
58:21Have you ever watched this happen before?
58:23This is amazing.
58:24You think this is going on all over the delta, miles and miles and miles of water just spreading
58:29everywhere at this rate.
58:32Incredible.
58:34And the team had managed to capture just a tiny part of it, revealing in intimate detail
58:41the character of the Great Flood.
59:11the Great Flood.