0:00:13 > 0:00:16This is the least known of Africa's great rivers.
0:00:18 > 0:00:21The Zambezi brings life to six countries
0:00:21 > 0:00:26and its reach spans half a million square miles of southern Africa.
0:00:26 > 0:00:30It's a river of thrilling spectacle
0:00:30 > 0:00:32and wild surprises.
0:00:48 > 0:00:51At times, the Zambezi's power can be almost overwhelming.
0:00:57 > 0:01:02Yet it can be just as challenging when its waters all but disappear.
0:01:14 > 0:01:19The fate of all life here is at the mercy of the ever-changing moods
0:01:19 > 0:01:21of this great river.
0:01:31 > 0:01:34In April, half a million tons of water
0:01:34 > 0:01:37pours over the Victoria Falls every minute.
0:01:39 > 0:01:41Just a few months later,
0:01:41 > 0:01:44the Zambezi's most famous landmark has dried up.
0:01:51 > 0:01:54By September, the drought is so intense
0:01:54 > 0:01:59that for much of its course, the river has shrunk to almost nothing.
0:02:00 > 0:02:03This leaves a great swathe of south-east Africa
0:02:03 > 0:02:06deprived of its life-giving waters.
0:02:09 > 0:02:10During the wet season,
0:02:10 > 0:02:13the Zambezi flows for 1,600 miles
0:02:13 > 0:02:16from its source in the Zambian Highlands
0:02:16 > 0:02:20to the coast of Mozambique, where it empties into the Indian Ocean.
0:02:22 > 0:02:26But by the end of the dry season, the river barely flows at all...
0:02:26 > 0:02:31leaving the land at the mercy of a blistering sun.
0:02:41 > 0:02:46The dwindling river draws in thirsty animals from near and far.
0:02:49 > 0:02:52Its banks see a constant flow of traffic.
0:03:05 > 0:03:06The desperate search for food
0:03:06 > 0:03:10can keep elephants away from the river for days at a time...
0:03:17 > 0:03:21..which must make their brief return visits all the sweeter.
0:03:34 > 0:03:37Buffalo put in more regular appearances...
0:03:39 > 0:03:42..dipping into the river morning and evening.
0:03:51 > 0:03:54Hippos are even more tightly bound to the river.
0:03:57 > 0:03:59As the Zambezi shrinks,
0:03:59 > 0:04:02these dedicated bathers are forced to crowd together
0:04:02 > 0:04:04into what pools remain.
0:04:11 > 0:04:14HIPPO GRUNTS
0:04:16 > 0:04:22They've spent the cooler night wandering the banks looking for food.
0:04:25 > 0:04:28Daybreak sees them heading back to the river.
0:04:32 > 0:04:34HIPPO GRUNTS
0:04:37 > 0:04:39Hippos have thick, blubbery skin
0:04:39 > 0:04:41and no sweat glands.
0:04:41 > 0:04:44So overheating can be a real problem.
0:04:46 > 0:04:49Wallowing through the heat of the day is one way
0:04:49 > 0:04:51to help them keep their cool.
0:04:54 > 0:04:58One hippo is late back from its nocturnal wanderings,
0:04:58 > 0:05:02only to find its way to the river barred.
0:05:12 > 0:05:14These hyenas are really pushing their luck,
0:05:14 > 0:05:16picking on such an enormous victim.
0:05:19 > 0:05:23But when times are tough, no opportunity can be overlooked.
0:05:23 > 0:05:26HYENAS SCREAM
0:05:37 > 0:05:40Hippos only feel safe in deep water.
0:05:40 > 0:05:43But this late in the dry season,
0:05:43 > 0:05:46that's a commodity in very short supply...
0:05:48 > 0:05:52..forcing thousands to share the narrowing channels
0:05:52 > 0:05:54that feed the Zambezi.
0:05:58 > 0:06:01This stressful overcrowding leads to fighting
0:06:01 > 0:06:04and the inevitable casualties.
0:06:13 > 0:06:16The smell of death draws out the river's scavengers.
0:06:30 > 0:06:32Within a few hours,
0:06:32 > 0:06:37over 100 crocodiles have converged on the carcass from far and wide.
0:06:44 > 0:06:48The younger ones hold back, while the larger crocodiles
0:06:48 > 0:06:50squabble over the choice cuts.
0:06:56 > 0:07:01Crocodiles are true survivors, able to go for months between meals.
0:07:03 > 0:07:07So this one chance to feed will be enough
0:07:07 > 0:07:10to get many through the hard times.
0:07:18 > 0:07:21Others too are reaping the benefits of this overcrowding.
0:07:23 > 0:07:26Wherever there are hippos, there are oxpeckers.
0:07:27 > 0:07:31The hippos tolerate these birds because they remove ticks
0:07:31 > 0:07:34and other skin parasites.
0:07:34 > 0:07:36Their habit of picking at old wounds
0:07:36 > 0:07:41to lap up fresh blood is much less friendly.
0:07:44 > 0:07:48And hippos aren't the only choice open to these freeloaders.
0:07:55 > 0:08:00Buffalo are plagued by their attentions, as they poke and probe,
0:08:00 > 0:08:04feasting on bugs, dead skin, saliva...
0:08:04 > 0:08:08even earwax.
0:08:19 > 0:08:23Six months ago, these mud banks were completely underwater.
0:08:24 > 0:08:26But as the river level has dropped,
0:08:26 > 0:08:29carmine bee-eaters have moved in
0:08:29 > 0:08:31to stake their claims.
0:08:35 > 0:08:38Each nest hole must be dug anew each year,
0:08:38 > 0:08:43after the Zambezi has reshaped its banks during the flood season.
0:08:47 > 0:08:50Some colonies may contain several hundred pairs,
0:08:50 > 0:08:52all crowded together for safety.
0:08:57 > 0:09:00But the adults are still vulnerable to aerial attack.
0:09:04 > 0:09:07An African fish eagle has taken up residence.
0:09:07 > 0:09:10And it's developed a real taste for bee-eaters.
0:09:10 > 0:09:13BIRDS CHIRP
0:09:20 > 0:09:24Its feet are designed for grappling with slippery fish,
0:09:24 > 0:09:27but they're just as good at snatching panicking birds.
0:09:39 > 0:09:41It's another of the Zambezi's residents,
0:09:41 > 0:09:45adaptable enough to make the most of any chance that presents itself.
0:09:50 > 0:09:54By October, the river has pretty much reached rock bottom.
0:10:03 > 0:10:06Out on the Zambezi's floodplain,
0:10:06 > 0:10:09the intense heat is sucking the last water holes dry.
0:10:11 > 0:10:16This warm, muddy water holds little oxygen for trapped catfish,
0:10:16 > 0:10:20but asphyxiation is the least of their problems.
0:10:23 > 0:10:26Marabou storks gather around the shrinking pool.
0:10:30 > 0:10:33Smaller catfish can burrow into the mud to escape
0:10:33 > 0:10:39and will even travel short distances over land to reach new pools.
0:10:39 > 0:10:42But the larger ones have nowhere to hide.
0:10:48 > 0:10:52In the heat, their fate is sealed.
0:10:57 > 0:11:00Several hundred miles further inland,
0:11:00 > 0:11:02and upstream from the Victoria Falls,
0:11:02 > 0:11:06the situation around the Zambezi is just as desperate.
0:11:09 > 0:11:13Along the river's banks, the land is turning into a dust bowl.
0:11:15 > 0:11:19As the grass withers and dies, there's little left to eat.
0:11:20 > 0:11:22Everything is hanging on,
0:11:22 > 0:11:26hoping the river will soon revive their fortunes.
0:11:33 > 0:11:37Wandering guinea fowl disturb a pack of hunting dogs.
0:11:42 > 0:11:45The birds are of only passing interest.
0:11:45 > 0:11:47These dogs are after bigger prey.
0:11:51 > 0:11:56The pack exchange greetings as they steel themselves for the chase.
0:11:59 > 0:12:02The dogs have been waiting for the cool of the evening...
0:12:02 > 0:12:03but now it's time.
0:12:06 > 0:12:08The pack is led by an alpha pair.
0:12:08 > 0:12:10They decide when to move and what to hunt.
0:12:24 > 0:12:29As they close in, the pack splits up, trying to outflank their prey.
0:13:06 > 0:13:07Impala have speed.
0:13:15 > 0:13:18But the dogs can run at 30 miles an hour...
0:13:21 > 0:13:25..and have incredible stamina, as well as guile.
0:13:27 > 0:13:31In their panic, the impala runs straight into the trap.
0:13:35 > 0:13:37DOGS WHIMPER
0:13:39 > 0:13:43Three quarters of all wild dog hunts end in a kill.
0:13:49 > 0:13:53A group this size needs to kill every day.
0:13:54 > 0:13:58And a river-side territory means they fare better than many.
0:14:08 > 0:14:10Away from the river, the land is parched.
0:14:18 > 0:14:21Life is a challenge for even the biggest
0:14:21 > 0:14:24and smartest of the Zambezi's inhabitants.
0:14:32 > 0:14:34With the river side vegetation exhausted,
0:14:34 > 0:14:38hungry elephants have been forced away from the river
0:14:38 > 0:14:41in search of food.
0:14:45 > 0:14:48They can't afford to ignore anything.
0:14:48 > 0:14:51Even a toppled tree gets the herd excited.
0:15:02 > 0:15:05Little ones need to learn these twigs are edible
0:15:05 > 0:15:09and some moisture can still be found in the bark.
0:15:13 > 0:15:19But the adults need up to 200 kilos of forage every day...
0:15:23 > 0:15:27..and lots of water to help digest such a high-fibre meal,
0:15:27 > 0:15:32which means repeatedly trekking back and forth to the river.
0:15:36 > 0:15:40Three or four days without a drink is just about their limit.
0:15:46 > 0:15:50Local knowledge can make all the difference to survival.
0:15:50 > 0:15:54It's intelligence the herd matriarchs have accumulated
0:15:54 > 0:15:56over decades of wandering the plains.
0:16:02 > 0:16:07Young calves begin to absorb this survival know-how
0:16:07 > 0:16:09as they march at their mothers' side.
0:16:15 > 0:16:20A fully grown elephant can easily drink 100 litres of water
0:16:20 > 0:16:21in a single visit.
0:16:26 > 0:16:29There's little time to linger,
0:16:29 > 0:16:33although some seem reluctant to leave the comfort of the river.
0:16:36 > 0:16:39But soon, this ordeal will be over.
0:16:40 > 0:16:43The mood of the Zambezi is about to change.
0:16:44 > 0:16:47The first signs of that change
0:16:47 > 0:16:51can be seen above the rolling hill country of northern Zambia.
0:16:51 > 0:16:56The Kaleni Hills rise just 1,500 metres above sea level,
0:16:56 > 0:17:01but they are the green heart that will pump life back into the Zambezi.
0:17:06 > 0:17:09Above these hills, powerful and opposing trade winds
0:17:09 > 0:17:13begin to converge.
0:17:15 > 0:17:19These collisions generate huge thunderclouds and torrential storms.
0:17:33 > 0:17:38These first downpours mark the rebirth of the Zambezi.
0:17:41 > 0:17:44From these hidden springs,
0:17:44 > 0:17:48the great river begins to trickle its way to the sea.
0:17:51 > 0:17:52As the streams combine,
0:17:52 > 0:17:56the rejuvenated Zambezi begins to gather strength
0:17:56 > 0:17:58as it curves westward into Angola.
0:18:03 > 0:18:08These forest glades are the last stronghold of giant sable antelopes.
0:18:14 > 0:18:17The darker males carry huge, curved horns
0:18:17 > 0:18:20that can grow to over a metre and a half.
0:18:26 > 0:18:30For 30 years, there were no sightings of these animals.
0:18:30 > 0:18:32Then, in 2005,
0:18:32 > 0:18:36this one herd was rediscovered.
0:18:39 > 0:18:41With only a few hundred left,
0:18:41 > 0:18:45every new addition helps bolster the sables' dwindling numbers.
0:18:47 > 0:18:52For the moment at least, these highly-endangered antelopes
0:18:52 > 0:18:55have found a sanctuary on the banks of the Zambezi.
0:18:59 > 0:19:03As the river swings back east and re-enters Zambia,
0:19:03 > 0:19:07it leaves the sable and the forests far behind.
0:19:09 > 0:19:14The growing Zambezi begins to wind its way across the Barotse Plains.
0:19:17 > 0:19:21These first rainstorms have partially refilled
0:19:21 > 0:19:23some of the long-dry water holes.
0:19:24 > 0:19:26After months on the move,
0:19:26 > 0:19:30the pressure on the great herds of buffalo finally eases.
0:19:43 > 0:19:45As the plains turn from brown to green,
0:19:45 > 0:19:51the buffalo can settle down to the serious business of eating,
0:19:51 > 0:19:55spending up to 18 hours every day grazing the new grass.
0:20:04 > 0:20:09The Losi people have lived alongside the Zambezi for generations,
0:20:09 > 0:20:11adapting to it many moods.
0:20:17 > 0:20:21Before the water levels begin to rise, there's time to visit
0:20:21 > 0:20:24a favourite fishing hole to plunder the last of the trapped catfish.
0:20:46 > 0:20:49Soon, this grassland will be unrecognisable
0:20:49 > 0:20:53and the Losi will be forced to move on to pastures new.
0:21:01 > 0:21:04They will not be the only ones on the move.
0:21:09 > 0:21:11As the rains gather in strength,
0:21:11 > 0:21:14others are being drawn towards the Zambezi.
0:21:18 > 0:21:22Small groups of blue wildebeest begin to arrive,
0:21:22 > 0:21:26after a 200-mile journey south from the forests of Angola.
0:21:33 > 0:21:3530,000 will eventually gather here.
0:21:44 > 0:21:49It's one of the largest, yet least known migrations in Africa.
0:21:56 > 0:22:00They are here to graze the fresh grass...
0:22:00 > 0:22:02and to calve.
0:22:07 > 0:22:12Almost all wildebeest calves are born within a three-week period,
0:22:12 > 0:22:15flooding the Zambezi's plains with new life.
0:22:22 > 0:22:26But they have already attracted some unwelcome attention.
0:22:28 > 0:22:32A clan of hyenas begin to shadow the growing herds.
0:22:35 > 0:22:38Their hunting strategy is simple...
0:22:40 > 0:22:41Get the herd moving.
0:22:43 > 0:22:45Look for a weakness...
0:22:48 > 0:22:49..then strike.
0:22:52 > 0:22:56The hyenas move in amidst the chaos, searching for a victim.
0:23:07 > 0:23:10The calf makes it back to the safety of the herd.
0:23:11 > 0:23:15Its mother is not so lucky.
0:23:20 > 0:23:24The clan soon gather around the downed wildebeest.
0:23:28 > 0:23:33Despite having so much choice, nothing is wasted.
0:23:35 > 0:23:39All too soon, the wildebeest will move on.
0:23:40 > 0:23:43And the hyenas' time of plenty will disappear.
0:23:52 > 0:23:55By January, the storms are coming thick and fast.
0:24:10 > 0:24:14The river channel can barely contain the torrent.
0:24:29 > 0:24:30After months with so little water,
0:24:30 > 0:24:33the Barotse's residents are about to be confronted
0:24:33 > 0:24:35by a very different Zambezi.
0:24:43 > 0:24:46The flood surges out over the river banks,
0:24:46 > 0:24:49inundating thousands of square miles.
0:24:50 > 0:24:52Almost overnight,
0:24:52 > 0:24:56the grassy plains are transformed into a shallow inland sea.
0:24:58 > 0:25:02More migrants arrive, following the advancing flood...
0:25:05 > 0:25:07..their growing numbers adding
0:25:07 > 0:25:11to one of the greatest gatherings of birds anywhere on the planet.
0:25:16 > 0:25:20The rising water has suddenly got everything on the move.
0:25:27 > 0:25:30Insects, frogs and fish all make their way
0:25:30 > 0:25:33onto the flooded plains to breed.
0:25:33 > 0:25:36Easy pickings for the hordes of water birds.
0:25:37 > 0:25:40Even ground hornbills take advantage,
0:25:40 > 0:25:41stalking the shallows.
0:25:46 > 0:25:50Spoonbills sift the grasses for snails and minnows,
0:25:50 > 0:25:54while yellow-billed storks tackle bigger fish.
0:26:05 > 0:26:08But while these new arrivals make merry,
0:26:08 > 0:26:11others are now forced to move on as the waters deepen.
0:26:15 > 0:26:19The buffalo herds bulldoze their way towards higher ground.
0:26:30 > 0:26:33The blue wildebeest continue their wanderings.
0:26:33 > 0:26:37It will take five months for them to complete their return journey
0:26:37 > 0:26:40back to the Angolan hills.
0:26:42 > 0:26:44Lechwe antelope are in their element.
0:26:47 > 0:26:50Strong swimmers, they never stray far from water.
0:26:52 > 0:26:56But even they must move to keep pace with the rising tide.
0:27:00 > 0:27:05The relentless Zambezi forces both predator and prey into full retreat.
0:27:24 > 0:27:28April marks high water on this stretch of the Zambezi.
0:27:34 > 0:27:37The river's floodplain is now 20 miles wide.
0:27:42 > 0:27:46It takes weeks for the floods to cross these flat expanses,
0:27:46 > 0:27:51as if the river is drawing breath before plunging on toward the sea.
0:28:00 > 0:28:04The Losi too have learnt to adjust to the rhythms of the great river.
0:28:11 > 0:28:14Their villages first become waterlogged...
0:28:16 > 0:28:19..then, gradually, submerged.
0:28:25 > 0:28:30Soon, they will abandon their huts, driven out by the rising tide.
0:28:33 > 0:28:37But they can't just up sticks and leave.
0:28:37 > 0:28:41By tradition, they must first wait for the signal from their king.
0:28:45 > 0:28:50Today has been decreed as the moving day - the Kuomboka.
0:28:52 > 0:28:56The word means literally "to get out of the water."
0:28:57 > 0:29:02CHEERING
0:29:04 > 0:29:09It marks the time when the entire community moves to higher ground
0:29:09 > 0:29:11and in some style.
0:29:15 > 0:29:17An elephant decorates the King's barge.
0:29:19 > 0:29:22A crane perches on the roof of the Queen's.
0:29:31 > 0:29:36100 men peddle each of the royal barges across the flooded grasslands.
0:29:45 > 0:29:48It takes hours in the boiling heat
0:29:48 > 0:29:52and humidity to reach their summer villages on the edge of the plains.
0:29:56 > 0:29:59The Losi may be away for six months or more,
0:29:59 > 0:30:02but it's a disturbance well worth putting up with.
0:30:06 > 0:30:09The silt left behind after the floodwaters recede
0:30:09 > 0:30:14invigorates the plains, preparing it for the returning villagers
0:30:14 > 0:30:17to plant their crops and graze their animals.
0:30:19 > 0:30:24The Kuomboka is a celebration of the gifts the Zambezi brings
0:30:24 > 0:30:26to this part of Africa
0:30:26 > 0:30:30and of how much the rise and fall of the river dictates life here.
0:30:34 > 0:30:40For now, the Losi villages stand empty, deserted by the people
0:30:40 > 0:30:43and their livestock.
0:30:43 > 0:30:45But there is life here still.
0:30:55 > 0:30:58New lodgers flood into the abandoned settlements.
0:31:02 > 0:31:07Carp, minnows and cichlids pick over the remnants of village courtyards.
0:31:14 > 0:31:18The flooded houses make perfect breeding grounds
0:31:18 > 0:31:21for many Zambezi fish.
0:31:21 > 0:31:24Others use them as shelter from predatory tigerfish.
0:31:27 > 0:31:29But stray too far from cover
0:31:29 > 0:31:32and there are other hunters waiting to drop in.
0:31:50 > 0:31:52Able to hover and eat on the wing,
0:31:52 > 0:31:55pied kingfishers are perfectly at home
0:31:55 > 0:31:57fishing over the flooded grasslands.
0:32:04 > 0:32:07As the floodwater finally reaches the southern end
0:32:07 > 0:32:09of the Barotse plain,
0:32:09 > 0:32:13it is gently funnelled back into the main channel of the Zambezi.
0:32:15 > 0:32:18Now, over 700 miles from its source,
0:32:18 > 0:32:22the great river gathers itself for the next stage of its journey.
0:32:24 > 0:32:27Heading east again, the Zambezi begins cutting through
0:32:27 > 0:32:30the tough volcanic rocks of the Tonga Plateau.
0:32:35 > 0:32:39Ahead, a cloud rises half a mile into the sky.
0:32:41 > 0:32:43It's not smoke from a bushfire,
0:32:43 > 0:32:46but spray.
0:32:46 > 0:32:49Visible from 20 miles away,
0:32:49 > 0:32:53this cloud signals the most famous landmark on the Zambezi.
0:32:57 > 0:33:00This is Mosi-oa-Tunya -
0:33:00 > 0:33:02the smoke that thunders.
0:33:05 > 0:33:08To the wider world, these are the Victoria Falls.
0:33:24 > 0:33:28In full flood, this is the largest sheet of falling water in the world.
0:33:34 > 0:33:40Over half a million cubic metres of water pour over the lip every minute.
0:33:57 > 0:34:01At this time of year, the falls are over a mile wide.
0:34:10 > 0:34:13And the cascade throws up enough spray to sustain
0:34:13 > 0:34:17a unique rainforest along the Zambezi's banks.
0:34:31 > 0:34:35Once the surge has passed, the local fishermen move in to try
0:34:35 > 0:34:41their luck, in what must be the most exclusive fishing holes in the world.
0:34:44 > 0:34:49Generations have made the precarious journey out to this pool.
0:34:53 > 0:34:58One false move and it's a drop of over 100 metres onto the rocks below.
0:35:10 > 0:35:13The Victoria Falls are a pivotal point on the river.
0:35:15 > 0:35:20From here, the Zambezi leaves the wild plains far behind
0:35:20 > 0:35:23and powers on towards a new and very different world.
0:35:35 > 0:35:38Below the falls, the river cuts through
0:35:38 > 0:35:42the first of several deep gorges.
0:35:44 > 0:35:48The Zambezi is squeezed into a channel just 100 metres wide.
0:35:54 > 0:35:57The power of the compressed river is immense.
0:36:10 > 0:36:12Over millions of years,
0:36:12 > 0:36:17this slow attrition has carved a series of steep-sided canyons.
0:36:22 > 0:36:28Deep and inaccessible, these gorges have been cut a centimetre at a time
0:36:28 > 0:36:31by the raw energy of the river in full flood.
0:36:39 > 0:36:44For over 100 miles, the Zambezi zigzags its way east,
0:36:44 > 0:36:47driving on towards the coast.
0:37:12 > 0:37:15But as the river bursts from the last of these canyons,
0:37:15 > 0:37:19the current slackens
0:37:19 > 0:37:23and the flood lost in the deep waters of Lake Kariba.
0:37:26 > 0:37:31Over 180 miles long, this is one of the largest lakes in Africa.
0:37:34 > 0:37:35But only 60 years ago,
0:37:35 > 0:37:39these islands were hilltops, because this lake is a recent addition
0:37:39 > 0:37:43to the Zambezi's ancient course.
0:37:45 > 0:37:49Holding back all this water is the Kariba Dam.
0:37:58 > 0:38:01It was the first of several huge dams which now help control
0:38:01 > 0:38:04the flow of the Zambezi...
0:38:07 > 0:38:11..converting the elemental energy of the river into electricity
0:38:11 > 0:38:14for Zambia, Zimbabwe and South Africa.
0:38:19 > 0:38:23After the dam was completed in 1959,
0:38:23 > 0:38:27it took just four years for Lake Kariba to fill.
0:38:31 > 0:38:34As the waters backed up behind the new dam,
0:38:34 > 0:38:38a massive rescue mission known as Operation Noah
0:38:38 > 0:38:42was mounted to help animals caught out by the rising tide.
0:38:48 > 0:38:51A group of dedicated wildlife rangers
0:38:51 > 0:38:53moved in to deal with the stranded animals
0:38:53 > 0:38:55ELEPHANT TRUMPETS
0:39:01 > 0:39:03Larger animals were sedated...
0:39:06 > 0:39:11..then moved to newly-established national parks along the lake shore.
0:39:13 > 0:39:16Small animals were stampeded into nets.
0:39:19 > 0:39:22DEER WHINE
0:39:24 > 0:39:27It was a dangerous business for all involved.
0:39:34 > 0:39:38It was the first time such an ambitious wildlife rescue
0:39:38 > 0:39:40had ever been attempted,
0:39:40 > 0:39:43but Operation Noah was hailed as a triumph.
0:40:00 > 0:40:02Over five years,
0:40:02 > 0:40:06more than 6,000 animals were removed to safe ground.
0:40:15 > 0:40:17RHINO GRUNTS
0:40:21 > 0:40:23RHINO ROARS
0:40:27 > 0:40:30Although clearly some were less than grateful for the efforts
0:40:30 > 0:40:33made on their behalf.
0:40:35 > 0:40:37RHINO ROARS
0:40:43 > 0:40:46While the rescued animals lived to fight another day,
0:40:46 > 0:40:50the dam itself changed the Zambezi's character forever.
0:40:53 > 0:40:57Robbing the river of much of its essential wildness.
0:40:57 > 0:41:01Today, the seasonal floods on the lower reaches of the river
0:41:01 > 0:41:04are no longer dictated by nature,
0:41:04 > 0:41:07but largely controlled by engineers.
0:41:10 > 0:41:13Yet enough water is still released from the dam
0:41:13 > 0:41:16to keep the river flowing
0:41:16 > 0:41:21and every rainy season, the Zambezi spills out of its main channel
0:41:21 > 0:41:25and floods into a series of ancient lakes and stream beds.
0:41:27 > 0:41:30These are known as the Mana Pools.
0:41:31 > 0:41:33ELEPHANT GRUNTS
0:41:33 > 0:41:37The barren earth bursts into life with grasses
0:41:37 > 0:41:40and seeds that have lain dormant for months.
0:41:42 > 0:41:45This flush of green draws in game animals
0:41:45 > 0:41:47all along the fringes of the river.
0:41:51 > 0:41:55Young hippos hide away in the quieter backwaters.
0:41:57 > 0:42:02Many of these pools are now choked with water hyacinth, a fast-growing,
0:42:02 > 0:42:07invasive weed, introduced from the Amazon in the 19th century.
0:42:13 > 0:42:16But these floating mats block out the light
0:42:16 > 0:42:20and starve the water of oxygen, choking all other life.
0:42:25 > 0:42:29Although hippos and elephants seem to adore it.
0:42:32 > 0:42:37So the more they can eat, the better it is for the health of the pools,
0:42:37 > 0:42:40but they have quite a job on their hands.
0:42:43 > 0:42:47The flooding draws even reluctant bathers into the water.
0:42:50 > 0:42:52INSECTS BUZZ
0:42:53 > 0:42:57Baboons certainly don't enjoy getting wet,
0:42:57 > 0:43:02but the chance to feast on snails and flowers proves irresistible.
0:43:12 > 0:43:15Along the tree-lined banks, other Zambezi residents
0:43:15 > 0:43:17seem much more at home.
0:43:21 > 0:43:23Fish eagles don't miss a trick.
0:43:26 > 0:43:30With the bee-eaters long gone, they have turned their attentions
0:43:30 > 0:43:33to the shoals of fish that gather in the shallows.
0:44:14 > 0:44:16They can even turn the tables
0:44:16 > 0:44:21on the tigerfish, one of the most voracious of the Zambezi's predators.
0:44:27 > 0:44:29BIRDS SQUAWK
0:44:31 > 0:44:35For a brief moment, the flooded pools are a magnet for many
0:44:35 > 0:44:37along the stretch of the Zambezi.
0:44:41 > 0:44:45Smart hunters stake out the water holes.
0:44:48 > 0:44:51Waiting and watching.
0:44:58 > 0:45:00These buffalo are nervous.
0:45:05 > 0:45:07They sense something is not right.
0:45:14 > 0:45:17They hightail it for cover.
0:45:36 > 0:45:40When threatened, buffalo bunch in a defensive group,
0:45:40 > 0:45:45with the calves gathered together and larger adults running shotgun.
0:45:48 > 0:45:52The lion is persistent, but when he catches up,
0:45:52 > 0:45:55one of the herd's enforcers proves more than a match.
0:46:03 > 0:46:05The rest of the herd move in as back-up.
0:46:18 > 0:46:22Buffalo are notoriously bad-tempered
0:46:22 > 0:46:24and quite capable of dispatching a lion.
0:46:28 > 0:46:32But today, it's only his pride that's been injured.
0:46:35 > 0:46:40After months of rain, the Zambezi is about to change moods once again.
0:46:48 > 0:46:51Storm clouds still build over the river each afternoon,
0:46:51 > 0:46:54but these last downpours have lost much of their power.
0:47:00 > 0:47:03The rain does little but kick up the dust.
0:47:10 > 0:47:12ELEPHANT GRUNTS
0:47:12 > 0:47:15All along the Zambezi,
0:47:15 > 0:47:20animals once again start preparing for harder times.
0:47:20 > 0:47:23But on one of the river terraces, a rare treat.
0:47:23 > 0:47:26An ancient fig tree has burst into fruit.
0:47:28 > 0:47:33A Trumpeter Hornbill shares the figs with a troupe of baboons.
0:47:39 > 0:47:42Fig trees can crop at any time of the year
0:47:42 > 0:47:45and these fruits always attract a crowd.
0:48:00 > 0:48:04As the heat intensifies, acacias begin shedding their seed pods.
0:48:07 > 0:48:10These are irresistible to bull elephants.
0:48:11 > 0:48:15In a good year, one tree may produce 300 kilos of seeds.
0:48:17 > 0:48:21For the tree, it's a great way to spread its seeds.
0:48:21 > 0:48:25For the elephants, these are rare and welcome morsels,
0:48:25 > 0:48:27packed full of energy.
0:48:32 > 0:48:35It's a chance for everyone to stock up.
0:48:42 > 0:48:46There are no giraffes here, so every extra centimetre gained
0:48:46 > 0:48:50gives these bulls exclusive access to more food.
0:48:54 > 0:48:58But it can be a precarious balancing act.
0:49:04 > 0:49:08Some elephants go to extraordinary lengths to reach the best leaves.
0:49:10 > 0:49:12ELEPHANT ROARS
0:49:18 > 0:49:21Bulls can weigh over 5,000 kilos
0:49:21 > 0:49:23and these acrobatics must place immense stresses
0:49:23 > 0:49:26on their spine and legs.
0:49:28 > 0:49:32But it's worth the risks to gather in the last of the greenery.
0:49:34 > 0:49:37Soon, life all along the Zambezi
0:49:37 > 0:49:42will become much more challenging, as the dry season begins to bite.
0:49:44 > 0:49:48Beyond the Mana Pools, the river continues eastwards
0:49:48 > 0:49:52through an ancient rift valley, heading towards Mozambique.
0:49:53 > 0:49:57The Indian Ocean is only a few hundred miles distant.
0:50:01 > 0:50:05But already the water level in the river is dropping.
0:50:09 > 0:50:11HIPPO GROANS
0:50:11 > 0:50:13Once again, hippos begin crowding
0:50:13 > 0:50:17into the deeper stretches of the Zambezi and its tributaries.
0:50:20 > 0:50:24Adults tend to hog the deeper parts of the river
0:50:24 > 0:50:27and the youngsters have learnt to give them a wide berth.
0:50:31 > 0:50:35They form their own gangs on the fringes,
0:50:35 > 0:50:39where their curiosity can get them into all sorts of scrapes.
0:51:02 > 0:51:07In the main channel, a dominant bull controls each stretch of deep water.
0:51:17 > 0:51:19He will tolerate others,
0:51:19 > 0:51:22as long as they behave themselves and defer to him.
0:51:32 > 0:51:35This muck flinging is all about intimidation.
0:51:42 > 0:51:44Crowded together, cheek by jowl,
0:51:44 > 0:51:47it's only a matter of time before tensions erupt.
0:51:55 > 0:51:57The shockwaves ripple down the line.
0:52:09 > 0:52:14Once the pecking order is restored, everyone settles down,
0:52:14 > 0:52:16but there's unfinished business here.
0:52:39 > 0:52:43Fights can last for hours and if opponents are well matched,
0:52:43 > 0:52:45can be to the death.
0:52:48 > 0:52:52The dominant male has reasserted his right to be the leader
0:52:52 > 0:52:56and so monopolise the females along this stretch of river.
0:53:01 > 0:53:04For a while longer, elephants can still take things easy.
0:53:06 > 0:53:09ELEPHANTS RUMBLE
0:53:09 > 0:53:13The bank-side vegetation is not yet exhausted,
0:53:13 > 0:53:16so they can stay close to the river.
0:53:17 > 0:53:22There's even the odd moment for them to indulge themselves.
0:53:22 > 0:53:27River mud makes an excellent screen against the blistering African sun.
0:53:32 > 0:53:35This very young calf is none too steady on its feet...
0:53:38 > 0:53:41..and soon needs rescuing by its ever-attentive mother.
0:53:46 > 0:53:48Elephants are great swimmers.
0:53:48 > 0:53:51River crossings hold few fears.
0:53:58 > 0:54:01Their snorkels allow them to continue
0:54:01 > 0:54:04even when fully submerged.
0:54:18 > 0:54:23There's time to spend a few minutes enjoying each other's company
0:54:23 > 0:54:25and the cool of the water.
0:55:04 > 0:55:07Soon, life will become much more serious.
0:55:16 > 0:55:20As food becomes harder to find, the elephants will again
0:55:20 > 0:55:23be forced to spend more and more time away from the river.
0:55:27 > 0:55:31As times get tougher, the Zambezi will once again become
0:55:31 > 0:55:34the vital lifeline on which all can depend.
0:55:38 > 0:55:40After 1,600 miles,
0:55:40 > 0:55:45the Zambezi is nearing the end of its epic journey across southern Africa.
0:55:52 > 0:55:55Here, on the flatlands of Mozambique,
0:55:55 > 0:55:59the great river mellows as it begins to divide into a maze
0:55:59 > 0:56:01of smaller channels.
0:56:03 > 0:56:07As the flow eases, silt carried from the heart of Africa
0:56:07 > 0:56:09begins to settle
0:56:09 > 0:56:14creating a huge delta that reaches out into the Indian Ocean.
0:56:19 > 0:56:23Today, this delta covers over 4,000 square miles,
0:56:23 > 0:56:26but just 60 years ago, it was twice this size.
0:56:30 > 0:56:34This dramatic decline is due mainly to the huge amounts of water
0:56:34 > 0:56:37being held back by the many dams upstream.
0:56:41 > 0:56:45Yet the river still empties vast quantities of fresh water
0:56:45 > 0:56:47into the Indian Ocean.
0:56:50 > 0:56:54But even as this mixes with the salt water, its journey is not over.
0:56:55 > 0:56:58Already, the heat of the sun is sucking droplets
0:56:58 > 0:57:02back up into the sky.
0:57:02 > 0:57:05These clouds are carried far inland by the trade winds,
0:57:05 > 0:57:10where they release their precious cargo as rain.
0:57:17 > 0:57:20Rain that replenishes the flow of the Zambezi,
0:57:20 > 0:57:23and so continues the endless recycling of water
0:57:23 > 0:57:25that is so crucial to life.
0:57:56 > 0:58:00Despite our best efforts to tame its many moods,
0:58:00 > 0:58:05the Zambezi remains one of Africa's greatest and wildest rivers.
0:58:20 > 0:58:23Subtitles by Red Bee Media Ltd