[simple gentle music] [tense tribal music] - [Christopher] Rivers snake through Botswana from mountains past the horizon.

As the water flows inland, it creates a spectacular delta, a permanent wetland in the heart of the Kalahari Desert.

It's called the Okavango.

But this world of water is no "safe" oasis.

[tense tribal music] Outside these rivers of water burn rivers of fire.

And the Kalahari hangs in the balance between desert and flood.

[gentle music] [wondrous music] This program was made possible by the Corporation for Public Broadcasting and by contributions to your PBS station from viewers like you.

Thank you.

[wondrous music] Where a great African river meets the parched heart of the Kalahari lies a land of profound beauty, the Okavango Delta.

Each year, the Okavango's waters flow across thousands of square miles of sand, giving birth to a flooded desert.

Within its breathtaking vistas lurk hidden dangers and rare and extraordinary creatures.

[gentle upbeat music] The Delta's skies ring with the cry of eagles and its waters teem with life.

There is no other system quite like it on earth, and few so complex.

On the northern edge of Botswana's Kalahari Desert, a river comes to a remarkable end, far from the sea.

Its waters spread across a vast flat plain, the desert interior of Southern Africa.

But for its first 60 miles, the river is confined between two parallel fault lines, in a region known as the Panhandle, where it meanders like a giant snake.

[gentle upbeat music] Besides an endless supply of water, the Okavango brings with it large amounts of silt, sand, and dissolved nutrients.

Together they produce a 5-million acre paradise in the middle of a dry world.

[birds squawking] [simple percussive music] Laid three months ago, crocodile eggs hatch when the waters start to rise.

Within weeks, the youngsters will disperse in every direction.

Most will succumb to predators; some may remain in the Panhandle.

And a few could end up hundreds of miles away, stranded in the desert.

Their fortunes will follow the water, in both its rise and fall.

The Panhandle's lush papyrus beds support a rich supply of insects and fish, a perfect nursery for small crocodiles.

Up to 10 feet thick in places, these great floating mats stretch as far as the eye can see, dwarfing even elephants.

As they forage, the elephants tear loose pieces of papyrus, launching a stowaway into the river.

[soft tribal music] [elephant trumpets] Heading into open water, this tiny crocodile drifts into danger.

[soft tribal music] Crocodiles rely on camouflage, instinct, and experience for survival.

Living long enough to acquire the experience is the challenge.

[tense music] The fish eagle can spot prey from thousands of feet in the air.

But young crocodiles have excellent vision too.

[tense music] [gentle tribal music] Still, out of the many thousands of crocodiles hatched in a season, only a few will grow to maturity.

As the waters peak, large sections of papyrus can break away and float downstream.

These circular islands often wash into small channels.

Blocked off, the channels may eventually vanish.

But elephants and hippos are always clearing old channels and forging fresh ones.

Where does all this water come from?

[elephant trumpets] For several months each year, rains in distant mountains, augmented by local rains, send a surge of water through the Panhandle.

It will take nearly half a year to spill out into the desert at the other end.

The waters spread underneath the papyrus mats, lifting the entire surface like a huge raft.

Though it looks solid, the papyrus is not firmly anchored to the ground.

[ethereal music] Beneath its protective roof, crocodiles and a wealth of other small creatures find shelter.

[ethereal music] The Panhandle acts as a giant filter for the Okavango.

Countless tiny papyrus roots comb the waters, extracting nutrients.

After flowing through many miles of roots, the waters emerge crystal clear.

At the edge of the papyrus lurks a hunter armed with razor-sharp interlocking teeth.

The tiger fish can strike with lightning speed both below the surface and above it.

The lily trotter is hunting too, unaware that it is also being stalked.

But most predators here are also prey.

[perky music] [soft music] Sunset brings a changing of the guard.

Eagles roost just as the fishing owls sound their booming calls.

[owl calling] [soft music] From below the papyrus, small fish and insects come out under cover of darkness.

They are the staple diet of little crocodiles.

In this watery world, the Pel's fishing owl is the eagle of the night.

With broad and powerful five-foot wings, and talons like grappling hooks, it lifts heavy prey straight out of the water.

Its main target is fish.

But a small crocodile will do.

[owl whining] This juvenile owl still has a lot to learn.

With its large, sensitive eyes, it must judge the refraction of the water's surface and catch a moving fish in the dark.

Diving into the water, it risks crocodile attack.

But the owl's special layer of downy feathers prevents it from sinking so it can make a quick escape.

The forlorn cry of the young owl signals his increasing hunger.

His parents are mating and no longer feed him.

Suddenly, he's on his own.

[fire roaring] A worthy opponent rises up to meet the waters.

Fire sweeps across the Panhandle, as if an epic battle is being waged between the water and the flames.

Together they will reshape this land of extremes.

[tense music] Oils in the lush green papyrus flare up, igniting the straw-like stalks.

[fire roaring] In the face of fire, escape is the only option.

[tense music] Even creatures like the puff adder that normally shy away from water must plunge in or perish.

[tense music] Out of this elemental struggle, the Okavango is reborn.

In dry periods, fires often burn all the way through the papyrus to the layer of peat lying on the Delta's floor.

[droning music] There it can smolder for months or even years, until it finally reaches the sand.

In this way, old, choked channels may be reopened, as advancing waters find new paths and directions.

The waters too sculpt the delta, redistributing sand and cutting through existing islands.

[birds singing and squawking] They carve out steep banks where rainbow-colored birds find safe nesting sites.

This haven for white-fronted bee-eaters will not last forever.

Next season, it may well crumble and wash away completely.

But for a while, the bee-eaters grace their sandy bank with dazzling colors.

[bee-eaters calling] Outside the bank's holes, danger is never far away.

Change is stirring throughout the Panhandle as the surge of water passes, and water levels lower.

While most fish breed in the dense underwater plants during high water, certain kinds of cichlid lay their eggs in open, shallow water.

Their nests pock-mark the sandy bottom.

Adults excavate bowl-shaped depressions for brooding their young.

[ethereal music] Since large predatory fish live primarily in deep water, the cichlid nurseries are out of their reach.

Nor can they hunt below the papyrus any longer.

For now the rafts have lowered and come to rest on the Delta's floor.

Thousands of small fish are forced into the open channels, exposing them to attack.

[ethereal music] The sudden availability of fish coincides with the mating season of the fish eagle.

[ethereal music] Without their papyrus shield, small fish cling to the roots on the river's edge.

They attract schools of hungry pike.

Tiger fish too patrol the fringes of the channel.

[ethereal music] Above them all, the fish eagle hunts the hunters.

[birds calling] [eagle calling] When fish are scarce, eagles need large territories.

But the profusion of fish in this channel has brought many pairs too close for comfort.

[birds calling] Their battle is a dizzying display.

By locking talons, fish eagles avoid seriously injuring each other.

But landing in the water presents a very real danger from crocodiles.

[birds calling] Besieged from above, it's trapped there.

[birds calling] Calm returns to the channel once more.

As it relaxes, the eagle fluffs its feathers, their color enhanced by the setting sun.

Lily covered backwaters provide good cover for the young crocodiles.

[birds calling] But fish eagles zero in on even the slightest movement.

[birds calling] A lucky escape.

And a valuable learning experience.

Fishing owls hide in the dark wooded islands along the channels during the day.

Owls and eagles are about the same size, but they are not equals.

Despite the easy mark, the owl will not hunt.

For any movement could set the eagle upon it, a fight the owl would lose.

[ethereal music] For the next few months, the filtered waters from the Panhandle fan out into the heart of the Delta.

This permanent wetland is always lush and green.

[ethereal music] Piercing sunlight and a slowing current foster a multitude of aquatic plants.

[ethereal music] Though still containing some dissolved minerals, these waters, once opaque, are now as clear as glass.

[ethereal music] The tranquil heart of the wetlands belongs to the plants.

But it is below the greenery that another key to this astonishing system is discovered: The plants sit above a dense layer of peat.

Up to six feet thick in places, it holds water like an immense sponge and retards its flow.

[ethereal music] Only very large animals can successfully navigate the wetlands.

With little game available, just a few crocodiles live here, though they can grow to enormous size.

They stalk the hippo paths which slice through the vegetation, revealing the peat and sand beneath.

[gentle tribal music] Elephants and hippos move easily through the maze of channels and dense plants as they search for food.

[gentle tribal music] Only one antelope resides in the deeper waters of the wetland: the graceful and elusive sitatunga.

Its elongated hooves keep it from sinking as it travels over marsh.

It's a prime target for big crocodiles.

Many young crocodiles have made it into the wetland.

[soft tribal music] Now double in size, they are no longer quite as vulnerable, at least to attacks by a saddlebill stork.

[soft tribal music] [gentle tribal music] On the fringes of the permanent wetland, lives another water antelope.

In huge herds, the red lechwe keep to the shallows where they are safe from most predators.

When the seasonal surge of water advances beyond the wetland, they will follow it to new grazing.

But even as the Okavango rises, water is being lost.

Exposed to the intense African sun and dry desert air, water evaporates so fast that this area should be a vast salt marsh.

But here, tree's suck up water faster than it evaporates causing salts to concentrate under islands.

The water is left fresh and pure, but the white salt islands are completely barren.

The white islands are isolated enough that bee-eaters will forego the safety of their vertical river banks and dig their nests on flat ground.

[bee-eaters chirping] [wind roaring] As the dry season takes hold in the Kalahari, elephants invade the wetland, seeking one of their favorite foods: the ripe fruit of the ivory palm.

But getting it requires timing and precision.

Shaking the tree is a skill, and some elephants are more talented than others.

Over the past six months, the surge of water has filtered through the Panhandle and been held back by the permanent wetland.

Now it seeps out into the dry flood plain.

A thin sheet of clean, clear water spills onto the grasslands and surrounds the wooded islands.

Coming at the driest time of year, long after the last meager desert rains, the water's arrival seems like magic.

Lions are symbols of big game country.

Within their territories, the lions now track the new waters' flow, anticipating the coming of the great herds for they know that where water flows, buffalo are soon to follow.

Older lions have seen this all before, but to a young cub, the transformation is astonishing and slightly suspicious.

[energetic tribal music] Along with the waters come a host of new visitors to the grassland.

A climbing perch can breathe air to escape the water and crawl to safety using special gill covers.

A distinct advantage in a land that is alternately wet and dry.

[energetic tribal music] The swelling waters flush insects, mice, and other small prey out of their grassy hiding places and into the open.

[gentle playful music] [birds chirping] These shallows, rich in prey, make good hunting for a young crocodile.

[tense music] [playful music] The unusual binocular vision of the climbing perch gives it pinpoint accuracy when leaping for insects.

[tense music] As the waters advance, the buffalo herds hasten across the parched plains to meet the filling pools.

For months, they have been confined to the sparse grazing on the edges of the permanent wetland.

Finally, they can wander the entire flood plain, cropping the fresh green shoots that spring up along the waters' path.

The lions of the Okavango do not shy away from water, especially if prey is on the other side.

Playful but alert, they watch the buffalo closely for signs of weakness.

[pulsing tribal music] [buffalo grunting] Wherever water goes, so go the crocodiles.

Wild dogs hunt here, too, treading the water cautiously.

They track the same prey, but often fall to crocodiles themselves.

[gentle tribal music] After several weeks, the waters inundate thousands of square miles of flood plain.

To travel anywhere, the animals must cross water.

Higher grounds become islands in the shallows.

Palm thickets provide good hiding places for prey and predator alike.

Later, this lioness may conceal her cubs in it.

But at the moment she's caught the scent of something interesting.

A warthog!

[tense music] As if to mark an end to paradise, the dry season has brought fire to this land of water.

Flames lay waste to the flood plain.

Exposed, brittle grass goes up like tinder.

[tense music] For now, the island of the lions remains unscathed.

[soft piano music] The lioness and her cubs seem unaware of the peril encircling them.

A strong wind and a live spark are all that stand between them and disaster.

[tense music] While most animals simply flee, the weak are easily trapped.

[tense music] Fire can work to a lion's advantage.

The lioness leaves for the hunt.

The cubs know to stay near the thicket till her return.

On an island untouched by fire, a sausage tree has attracted several animals.

These sausages, a prized fruit, are as tough as gourds.

Baboons have their own way of tearing them apart.

It takes two hands, one foot, and strong teeth.

[soft tribal music] With the water rapidly disappearing, there are few pools left deep enough for hippos.

Nearby, lechwe rest, never straying far from water, their only safe haven.

Soon, they must retreat to the permanent wetland.

[soft tribal music] [tense music] Predators too haunt these waters.

[tense music] [tense music continues] The age old rival of the wild dogs is all too ready to profit from their efforts.

[tense music] [gentle piano music] In warmer temperatures, many birds nest and snakes come out of hiding.

Nightjars lay their eggs directly on the ground, putting them well within reach of the aptly named egg-eater.

It crushes the egg with its vertebrae to release the contents.

[nightmarish music] Who would believe that so recently this was an Eden?

The herds take refuge in water, but it too is vanishing.

In the end, the waters are conquered by the dry season and the desert.

In the searing heat, an inch evaporates every day.

The rest sinks into the sand.

Soon all is lost save for a few large pools.

But in the waters' wake, succulent grass springs up, drawing enormous herds to feed.

[wondrous music] The changing conditions in the flood plain open up opportunities for some just as they close them for others.

[wondrous music] Vanishing pools are a catastrophe for fish, but a blessing to birds.

From far and wide, they come to harvest the annual bounty of stranded fish.

Even fish eagles leave their territories to take part.

The crocodiles remaining in the flood plain are forced into the shrinking pools.

[quick tribal music] Those that were once prey now turn predator.

The oppressive heat doesn't seem to dampen the spirits of the wild dogs.

They simply head for a mud bath.

Here's a curiosity, unfamiliar to the dogs.

Terrapins usually stay out of sight, deep in their pools.

With its home drying up, it must seek a safe place to wait for the water's return.

But a safe place may soon be beyond its reach.

[tense music] Displaced from its pool, a crocodile desperately looks for shelter.

[tense music] In huge swaths of the Delta, fire replaces water as the dominant force.

[tense music] [somber music] A lioness tries in vain to reach her cubs.

But their hiding place has gone up in flames.

[somber music] Every year, thousands of animals are destroyed by the infernos that consume the Delta.

Most are the young, the small, or the slow-moving.

[somber music] Sorrow for some is fortune for others.

For when cover is scarce for the mouse, food is plentiful for the yellow-billed kite.

[somber music] Softly the lioness calls for her cubs, while the jackal sounds an alarm.

[jackal calling] Most large animals escape unharmed.

They simply walk away faster than the flames, or they shelter in areas that have already burned.

[somber music] [gentle tribal music] Then out of the cinders, a small symbol of hope emerges.

[gentle tribal music] Now the hard times settle in for the creatures of the plains.

Trekking across miles of singed earth, the herds seek out water holes scattered through the grasslands.

And as always, the crocodiles are waiting in the last haven for the survivors of the heat and flames.

[soft tribal music] But even as these pools recede, the next surge of water is on its way.

Months from now, new waters will arrive to transform this changed wasteland.

For here where the Okavango's waters meet the Kalahari desert, the Delta is constantly recreated.

Fire and water ravage and renew, advance and retreat.

[gentle tribal music] But the waters are never defeated.

Faraway, rains are falling in the highlands and in time they will spill out into the Kalahari and flood the desert once more.

[gentle tribal music] This program was made possible by the Corporation for Public Broadcasting and by contributions to your PBS station from viewers like you.

Thank you.

[upbeat tribal music] [upbeat tribal music continues] [upbeat music]