Many Rivers To Cross (Off My List):Earth's Great Rivers.

Man, I love rivers. When I'm not walking along them, I'm attending talks about them. When I'm not attending talks about them, I'm visiting exhibitions about them and when I'm not attending exhibitions about them, I'm watching television programmes about them. Local rivers like the Thames, the Lea, and the Wey. Or global rivers like the Mekong or the Ganges. I just love rivers. If it was possible I'd probably eat a river.

Or maybe not. I washed the mud off my hands in the water of the Thames after slipping over on the footpath between Staines and Shepperton last month. It was cold. I can't imagine it would be very tasty. My mate Shep has walked the entire length of the Thames (one project I didn't join him on) and I once had the idea of walking the seven longest rivers in the UK (Severn, Thames, Trent, Great Ouse, Wye, Ure/Ouse, and Tay) but that never really came to anything. Replaced, probably sensibly, by regular TADS and London by Foot walks and projects like the London LOOP and the Capital Ring.

Three rivers I feel it's fairly safe to say I'll never walk the length of are the Nile, the Amazon, and the Mississippi. They're not short - and they're not always very accessible. I've at least had a glimpse of two of them. I saw the Nile on an Egyptian holiday in 2001 (from Cairo, Luxor, and Aswan) and I spent a few days and nights (mostly nights it felt like) with my friend Simon in New Orleans in 2011. You can't escape the influence of the Mississippi river there.

But to get a closer look at these three giants of the river scene I had to resort to television. BBC2's recent three part series Earth's Great Rivers was pitched somewhere between an educational show for children (no bad thing) and something David Attenborough would have approved of or even appeared on. Another David, Oyelowo, provided an authoritative  voice over that was made to sound a little over dramatic once the ominous , and sometimes daft, soundtrack was added.

Despite that minor objection, Earth's Great Rivers was addictive, engrossing, and informative. Taking the viewer on three epic journeys in less than three hours. The cities, ruins, humans, animals, and trees that have sprung up along the banks of these three rivers are as diverse as they are dramatic and each was touched on, if only briefly. That's the nature of rivers. They just keep flowing.

None more so than the Amazon. The biggest river on our planet. Including its tributaries (a remarkable 1,100 of them) it flows through nine countries (the actual Amazon covers just three:- all of which, I felt smug to discover, I've visited), it creates Earth's greatest rainforest and our greatest diversity of life. As well as, more difficultly for those who live along it, vast annual floods.

The four thousand mile journey along the Amazon begins with a single drop. Or, in truth, millions and millions of single drops. From the frozen glaciers of the Peruvian Andes and the cloud forest shrouded in mist, water falls from trees and creates the Amazon. A river that provides 20% of the Earth's fresh water.

In its water lurks all manner of natural marvels. One stretch is home to two metre long giant, and rare, river otters. We see them both fishing and teaching their young to fish. A skill it takes these otter cubs three years to master. Other legendary river monsters found in the Amazon include electric eels (capable of generating five hundred volts), pacu fish that weigh in at nearly four stone, and snakes that are in the reckoning for the title of world's largest. Anacondas that can grow to eighteen foot long.

Some headwaters are so inaccessible that their treasures are still being revealed to us. They host fish so new to science they're yet to be given a name. The riverbed in some parts of the Amazon is dotted with springs that filter the water, making it so clear that the fish swimming in it almost appear to be floating through the air. One tributary has no life whatsoever due to its boiling water. If a fish were to swim into it it would be poached alive.

Only recently mapped, it's now held to be the largest stretch of thermal river in the whole wide world. The indigenous Ashaninka people knew about it though. They've been visiting the river, the Shanay-Timpishka, for generations. Revered for its healing properties, a shaman testifies to the river's power and we learn how medicine is made by mixing the boiling water with local plants.

Barracudas and wolf fish swim up and down and stingrays camouflage themselves in the sand of the riverbed while green winged macaws bizarrely eat fresh clay, rich in salt, from the banks of the river. Far from the ocean, salt is a rare mineral.

In some ways, though, the ocean meets the river. The Amazon is so deep and wide that ocean going ships can sail two thousand miles inland far past the Amazon's largest city of Manaus. Manaus, with a population of over two million, is situated where the Amazon's largest tributary, the Rio Negro, joins the river. Rubber and gold brought people and money into Manaus and its Amazonas Opera House (built during the rubber boom of the late 19c) helped earn the city its nickname, 'the Paris of the Tropics'.

Perhaps less glamorously, the city is surrounded by cabbage farms and when the river floods these farms, the farmers turn to stilt gardens. Some suburbs of Manaus have experienced, recently, such powerful floods that every person living there has, at some point, lost their house. It's getting worse, rather than better, too.

More extreme. 200,000 square miles of flooded forests present a stark image of climate change. It's one this programme chooses to allude to rather than drill down on but it's there nonetheless. Instead, the film makers show us the incredible sight of fish swimming through the branches of underwater trees, and the world's largest river dolphins. Known, in Brazil, as botos. The dolphins are pink and they are the only dolphins whose adults have whiskers which, along with sonar, they use to locate prey.

Equally peculiar are the hoatzins. Or Amazonian stinkbirds. They've earned their none too flattering nicknames because of their habit of farting after eating gassy leaves. But it's not all scoffing leaves and letting off a Bronx cheer for the stinkbird. Spider monkeys eat their eggs so to avoid them, hoatzins nest in weak, and for monkeys difficult to reach, branches overhanging the river.

Difficult to reach for spider monkeys but now both eggs and, soon enough, newborn chicks are in reach of far more terrifying looking thirteen foot long black caimans. Evolution has provided the hoatzin with a solution as it so often does, and it's a very odd one. Baby hoatzins are born with claws on their wings so they can climb to safety in their infancy.

Before watching Earth's Great Rivers I had no knowledge whatsoever of the hoatzin's existence let alone their clawed wings. I'd also been unaware of the fact that the Amazon river was home to some spectacular beaches. On the shores of the lower Amazon (where the river is roughly fifteen miles wide) sits Alter de Chao. It looks a gorgeous place for a paddle, a cocktail, and a long lazy day in the sun.

Or, indeed, a great place to dress up as a pink boto before transforming into a handsome man in a white suit who comes on shore and tries to seduce young women. Successfully. Obviously. It's just one of the many parties, carnivals, competitions, and ceremonies that happen along the banks of the Amazon annually.

But no human show can compete with the one that nature puts on in this part of the world. Swimming tapirs, an underwater garden of sponges (some over one thousand years old), and a river that discharges more water into the ocean than the planet's next six biggest rivers combined. Superlatives, it seems, are endless. How can any other river compete with that?

The Nile, the world's longest, is up next - and the Nile certainly gives it a good go. From the equator to the Mediterranean via the Sahara, it brings life to the driest parts of the hottest continent on Earth and is home to elephants, hippos, and many other superstars of zoos and prey of big game hunters worldwide. The Nile has been held in awe for centuries. The ancient Greeks believed it flowed down from the mountains of the moon.

If reality could never quite be that impressive, it's still not bad. Nile water comes from many places but the highest up, and perhaps the most dramatic, are the Rwenzori Mountains of Uganda and DR Congo. As water flows down from the mountains it creates islands of floating papyrus that prove confusing for shoebill storks trying to make their homes, and food.

The storks use hippos as natural bulldozers to create channels to help them spot fish. Eventually these headwaters reach the huge Lake Victoria. It's almost the same size as Ireland and once water enters the lake it spends an average twenty-three years there before it leaves it. Once a year the sky above Lake Victoria fills with billions of flies. Swarms up to one hundred metres high perform a mating dance that is to be their final act.

Although it looks as itchy as hell, the flies are welcomed by fisherman (because they attract fish, the haul is phenomenal when the flies are out) as well as other locals (a flyburger contains five times more protein than a beefburger).

Thousands of streams enter Lake Victoria but there is just one way out:- The White Nile! The turbulent water and perilous rapids along this stretch are avoided by all but the most hardy, including endurance athletes in kayaks. Two of which we're briefly introduced to as they pass through bubbling white water in a feat that looks far too dangerous to be enjoyable.

Even they stop short before Murchison Falls where the fifty metre wide river is squeezed through a seven metre wide chasm before tumbling over one hundred and forty feet into Lake Albert. It's an impressive sight and as the river flows into, and out of, Lake Albert it becomes both a savanna and a home to giant nineteen foot long crocodiles.

A Nile monitor lizard smells crocodile eggs on the shore of the river and wanders over to inspect a potential meal before being chased off by a croc. A little later, the lizard returns to the eggs. It seems to know that, on land, crocodiles can die of heat exhaustion. The crocodile is plunged into a life or death dilemma. Or, more literally, death and death. Death of herself or death of her babies.

Eventually the lizard wins and devours the eggs. The watching mother crocodile has to hope not all sixty of them. Sixty eggs is too big a meal for lizards. But the problem is others like the taste of crocodile eggs too. A troop of baboons finishes off what's left of the omelettes. Only 2% of Nile crocodile eggs/babies make it to adulthood.

Even humans growing up under Idi Amin's rule had a (slightly) better chance than that. The 'butcher of Uganda', the 'last king of Africa', the 'man who ate his archbishop's liver', and the 'Lord of All the Beasts of the Earth and Fishes of the Seas' ordered the deaths of around 300,000 people and is highly ranked in most lists of the world's cruellest despots.

He was no nicer to animals than he was to people, regularly arranging hunts that devastated local wildlife. But it seems as if they're taking some kind of revenge now - while being surprisingly nice to each other at the same time. Pakuba Lodge, near Murchison Falls, was Amin's former country home. It now stands in ruins. But not empty. It is visited by, and overnighted in, warthogs, baboons, porcupines, and bats. A pangolin is also boarding at the time of our visit and we're shown remarkable nightcam footage of a passing leopard turning down the chance of an easy meal when it stumbles across a baby warthog.

As the White Nile enters South Sudan it reaches a swamp the size of England. The Sudd (Arabic for barrier) is a haven for Nile elephants. Elephants who spend a lot of time in the water. There are forty thousand muscles in an elephant's trunk so they act as excellent snorkels. Footage of a baby elephant taking its swimming lessons is just as adorable as you'd imagine it to be.

To the east of the White Nile stands 'Africa's water tower'. Storms in the Ethiopian highlands fill the Blue Nile. A waterway that some believe to be the biblical river that flowed from the Garden of Eden. In Gondar, there seems to be little dispute about the Blue Nile's sacred nature. Each January, Timkat is celebrated in the river's water. Thousands of orthodox Christians are baptised in the Nile water and, for a religious event, it looks a lot of fun.

I wondered how I had never heard of either Gondar or Timkat before. But before I had long to ponder that we were away from human life and back with the beasts again. Male weaver birds build intricate nests on the Blue Nile's banks ready for inspection by the females. Boring old brown nests just don't cut it. If a weaver bird wants a screw his nest must be seen to be green and new.

That's a little rhyme I made up to help me remember weaver bird mating rituals. I'm sure you'll find it useful. The Blue Nile and The White Nile join forces in Khartoum before crossing the Sahara, an expanse of sand the size of China where life seems an impossibility and perhaps, in some parts, would be if it was not for the line of blue that passes through the ocean of yellow.

The Nile is the only permanent river in all of Egypt so, for centuries - and still now for many, if you want to get anywhere you need a camel. Camels can drink an astonishing two hundred litres of water in three minutes (and then not need a drink for months). They're pretty big things but two hundred litres! Where do they store it all?

Moisture in camel dung attracts dung beetles (who have, and need, an incredible sense of smell). For many of these beetles living so far from rivers or seas, these balls of dung will be the only water they take in their entire lives. Hardly seems worth living. Certainly doesn't sound like something God would have bothered to create.

95% of the population of Egypt live on the banks of the Nile and twenty million of them in Cairo.It's the world's biggest desert city (though some metrics claim Karachi for this title) and although the Nile is still vital to everyday life for Egyptians and Cairenes it's not, I'd say, held with the same mystical reverence it was during the three thousand (!) years of the kingdom of Ancient Egypt when the Nile was called 'the mother of all men' and pharaohs claimed they had power over the river in order to win obedience over their subjects.

The massive muddy Mississippi's history, or at least the bits we learn about, don't go back so far and as such are more tied up with mercantile and artistic concerns. The 'heart and soul of the Deep South' has long given inspiration to writers (Herman Melville, Mark Twain, William Faulkner) and musicians (Johnny Cash, Paul Simon, Led Zeppelin) but Earth's Great Rivers' remit is more to look at the river itself and the flora and fauna that thrives (or struggles) on it than the great works of art that indirectly came from its waters.

The network of tributaries that make up the Mississippi stretches over thirty-one states. Hundreds of rivers come down from mountains and pass through prairies and we start our journey along the Mississippi in the Rockies, in Wyoming, with some brave, or crazy, ice climbers. While we can all admire the towering frozen waterfalls, some 200ft high, only the experienced would try and climb them. It looks terrifying. I'd rather be on a paddle steamer than sat at home watching television but my warm radiator and cup of tea start to look very comfortable when confronted with a sixty metre climb up an iced up waterfall!

Animals more used to the river than us humans include the bison, otters, and coyotes that live among the steaming geysers of Yellowstone Park which hosts a tributary (the Yellowstone) of a tributary (the Missouri) of the Mississippi. Coyotes don't catch fish naturally but, as the ground is frozen, needs must. After four hours of fruitless splashing around in the river, risking hypothermia, we see one finally catch a half metre long rainbow trout.

Bears, famously, have more skill than coyotes when it comes to catching fish and as tributaries flow from the east through Virginia and Tennessee to make up the Mississippi we're shown more amazing footage of Yogi's cousins as well as huge shoals of buffalo sucker fish and red salamanders known as hellbenders.

There's chub building 'nests' of pebbles and beavers in the basin erecting their own dams and lodges. Humans build even bigger dams. Some one hundred metres high. But the river finds a way. It either goes round the dam or pours through gaps in the dam. Fish are squeezed through with it and waiting on the other side? Hungry American white pelicans with three metre wingspans.

Human food passes down the Mississippi as well. Both grains and soya beans are grown here and transported down the river. The state of Wisconsin produces half of the world's cranberries. I love cranberry juice - and it's supposed to be good for gout too. Double win.

Mayflies don't need to worry about gout. They don't have time to worry about very much really. Their brains probably aren't even advanced enough to worry. Or to even understand the concept of worrying. Do animals worry? I digress. As ever. The mayfly nymphs live on the riverbed for two years before millions of fully grown mayflies emerge simultaneously, they mate, the females lay their eggs, and two days later they all die.

The life of a mayfly is short but at least they get some sex. Locks and dams convert the river, in places, into a virtual canal. The barges and tug boats that pass up and down the Mississippi's waters are very different to the paddle steamers of popular imagination. You know, like the one in Culture Club's Karma Chameleon video (which was actually filmed in Weybridge)!

With all this river trade it's no surprise that huge cities have grown up on the banks of the river (the Mississippi that is, not the Wey). St Louis is where the Missouri, its longest tributary, meets the Mississippi and, from there, the river flows into the Deep South. Swamp territory. Achafalaya is the largest swamp in the USA.

To my amateur eyes it looks like a textbook example of the bayou. Huge cypress trees covered in Spanish moss, herons, roseate spoonbills, white ibises, and metre tall egrets who, if they can find the well camouflaged baby alligators, will eat them. The beavers here are less worried about the fast flowing waters than the ones upstream. Their main concern is the parents of those baby gators. There are two million alligators in Louisiana. More than any other state.

New Orleans is the largest port in the Western hemisphere and the twenty-four mile Lake Pontchartrain Causeway (the longest bridge outside of Asia) brings traffic into the city from the north. Parts of the city are seven metres below the Mississippi's water level and the 1,600 miles of levee built to protect The Big Easy from flooding, as we all know, sometimes break. In 2005, Hurricane Katrina killed nearly one and half thousand people in New Orleans alone.

Of course the world, and that region more than many, is now on the brink of an even greater disaster as ice melts and sea levels rise and Earth's Great Rivers can't shirk the responsibility of mentioning this. On a global level the science is now all but certain. On a local level we see how man's interference, and man's attempts to control the flow of the river, has pushed swathes of the delta, including places where people used to live, permanently underwater.

It's a reminder that rivers can be deadly to go with the ongoing proof that they can also be beautiful, awesome, and life giving. Earths' Great Rivers contained footage that astounded and delighted me and via interviews with farmers, carnival kings, shamen, kayak guides, fishermen, photographers, and pilgrims as well as, of course, Oyelowo's narration, the story of these three great rivers were brought to life very impressively.

Each show ended with a ten minute add-on called Tales from the Riverbank which showed how they got some of the amazing wildlife shots and what risks the location photographers took to get them (quite a few in some cases). That's almost standard in these kinds of documentaries nowadays as well as it should be.

It's fascinating. But the fish, birds, reptiles, and mammals that live in these massive rivers, as well as the waterfalls and flood plains that make them up, are, of course, the real uncredited stars of the show. During three hours of intense river studies I wasn't, once, bored. But that's hardly surprising. As I said at the start I love rivers. Three thousand hours wouldn't be enough. Next river walk planned for next month.