Two new, similar features:
(subhead: "A huge, so far unreported, migration of displaced people is taking place at the end of the continent's longest-running civil war")
The Nile has witnessed more centuries of human eccentricity than any of the world's great rivers, but what it is now experiencing must rank high in its annals of misery. Hundreds of people laden with bags, bedding and bicycles wait disconsolately on wharves. Under the unremitting sun, anxious passengers crowd the flat decks of rickety barges meant only for cargo. Narrow launches are filled to the gunnels with sweating women and children on a precarious journey to places some have never seen.
Despite the hardship, this is part of the "peace dividend" from Africa's longest civil war. With a deal agreed between the largely Arab north and the southern rebel group, the Sudanese People's Liberation Movement, hundreds of thousands of the 4 million who fled the fighting have started the dangerous journey back.
Not all are going "home". More than two decades of conflict have produced a generation who were not born when their parents fled or are too young to remember anything except life in overcrowded camps. UN officials expect 580,000 to move between now and March in the start of what could be the world's biggest return of displaced people. They are going to one of Africa's poorest regions, where war has destroyed much of what was only a flimsy peacetime infrastructure of schools and health clinics.
Adding to the looming crisis is the so-called "Darfur distraction", the fact that the main donor governments have switched attention to the victims of Sudan's most recent war.
Overseeing a mound of suitcases and sacks filled with clothes, John Gideon helped his wife and six children clamber out of a launch at Malakal this week after an overnight journey from Melut. It was the latest ordeal on a 900-mile trek which included three different minibuses from Khartoum and will continue on a barge to his home town of Juba. Her arms swollen with mosquito bites, his wife dipped a bowl into the Nile, soaped and rinsed her children, and dressed them in clean outfits on the quayside. The family had to sell some of their bedding and furniture to raise the £250 needed for their fares.
Like half the war's displaced people, Mr Gideon escaped to Khartoum, where those from the south were herded into sprawling camps which the Arab authorities periodically cleared out, forcing people further into the desert, sometimes at gunpoint.
This year's peace deal allowed people to think seriously of returning to the south at last, but for many the trigger to pack up was an outbreak of violence after a helicopter crash in August killed John Garang, the SPLM's veteran leader. At least 200 people died and tensions have not abated.
"They burned the barber's shop I owned. I can't work there any longer," said Mr Gideon. "Life will be better than in the north. There we had to pay rent. In the south we will have our own place," his wife added.
Their journey so far has been without violence, but others are not so lucky. On the wharf at Kosti where people sometimes wait for three weeks for a place on a barge, a woman breastfeeding a child said soldiers often harassed women at night.
At N'bal, a remote area in the Nuba mountains, where up to 1,000 displaced people returned this week, Siham Alamba recounted how armed men in government uniforms and balaclavas had ambushed the lorry she was on. Several passengers were injured in shooting, while she and her 15 year-old son, who had money from his stepfather to pay for his schooling, were robbed along with the others.
"There were about 50 people on the truck with 16 small children. Once we got there we had to finish our journey with a 12-hour walk," she said.
The UN office for humanitarian affairs already has monitors to check the flow of people. It is planning to set up "way-stations" along the route to provide food and one night's shelter. It is also assembling a team of protection officers to work with the police. But it is waiting until at least next autumn before encouraging the displaced to return. Recognising the huge lack of schools, healthcare and food in the south, it is urging caution while promising the SPLM, now the official government there, that it will "assist spontaneous returns".
"If people come too fast, you will have problems," Dennis McNamara, the head of the UN's internal displacement division, warned SPLM officials on a visit to the south this week. "You will push the slums of Khartoum to become the slums of the south. We have to build up basic services or otherwise we may have an explosive situation. People will be very angry."
The SPLM has a dilemma. Reasons of pride make it want to see southerners return to help build its new state. It persuaded the north to give the south a share in Sudan's national government and oil wealth, or allow a referendum on secession in a few years' time. But senior officials recognise the south's severe shortages and the fact that, in Khartoum, in spite of discrimination by many local Arabs, most children in the camps go to school and many parents work. "Conditions in the north, although pathetic compared to what others have in the north, are better than the south," said Riek Machar, the south's new vice-president "The displaced expect schools, health services and so on. We're not encouraging them to come in one go."
Sudan's Arab leaders are also not pushing the displaced to return. With a tinge of glee, Abdel Haleem Ismail al Mudafie, Khartoum's governor, told reporters: "I have a strong belief many of these people will not go back south. They've never milked a cow. They don't own a goat. I told the UN three months ago, 'I'm dead sure that if you come in a year's time, few will have gone'."
The UN is taking no chances. Tens of thousands are already on the move, and unless pledges of international aid are soon delivered, this will be yet another crisis foretold but not forestalled.
Sudan was a British colony from 1898 to 1956. There has been a north-south civil war since independence. Fighting stopped in 1972 and resumed in 1983 when the north tried to impose Islamic sharia law on the south. An estimated 1.5 million have died in Africa's longest civil war, which is quite separate from the conflict in Darfur. A peace accord means hundreds of thousands of the 4 million who fled are returning home.
Millions of Sudanese displaced by Africa's longest war are now returning to southern Sudan, putting pressure on scarce resources in one of the poorest regions in Africa.
Many are coming from refugee camps in neighbouring countries, but the largest number were displaced to camps inside Sudan itself, mostly around the capital, Khartoum.
It is the largest movement of people in recent history. Nobody knows how many will come: the highest estimate is six million.
A peace deal was signed between the north and the south in January. But the return of those who fled north to escape the fighting began in earnest only after riots in Khartoum following the death of John Garang, the guerrilla leader who had signed the deal with the north.
Mr Garang died in a helicopter crash in August.
Southern Sudanese mobs rampaged through Khartoum, burning cars and property and killing people, when news broke of his death.
Gangs of northern youths then retaliated, destroying property in the camps housing southerners around the city.
Arriving on the quayside in the southern town of Malakal, John Gideon Jok said he decided to leave Khartoum only after his barber's shop was burnt down in the riots.
It took two long bus journeys and an 18-hour boat trip up the Nile to bring him to his home town, which he had not seen for many years.
His 23-year-old wife, Faiza, was born in the north and had never seen the south, her "homeland", before.
Faiza had hundreds of bites from malaria-bearing mosquitoes after their exposed journey, and one of their children could not open her eyes because of an infection.
Other travellers had suffered even more.
Although regular armies are no longer fighting, thousands of armed men in militia bands still roam the countryside, preying on vulnerable travellers. There have been many accounts of rape and robbery.
Starting from scratch
In a village in the Nuba mountains, a woman showed a wound on her forehead where she said she had been grazed by a bullet while travelling south.
The bus she was on was shot at and looted by a gang wearing army uniforms and masks to conceal their identities.
She was robbed of all she had saved in the camps, and cannot afford to educate her children.
She lives in one of the rare villages where there is a school.
Kenya is now providing English-speaking teachers, and training Sudanese teachers to construct the education system of the south from scratch. It will be a huge task.
Children who have been to northern schools where they teach in Arabic will have to start again.
Manuel da Silva, the UN official responsible for humanitarian affairs in Sudan, says that the task is not "reconstruction but construction".
He was a minister in the first post-war government in Mozambique after the civil war there, and has recent experience in Liberia - but he says that building southern Sudan is a much bigger task than either of those.
Wary of poor people moving into camps in the south and becoming dependant on aid, the UN is not promoting returns yet.
But it is trying to react quickly since people are coming anyway.
Riek Machar, a warlord turned politician who is now building the new government of the south, says that when the dry season starts in November, people will come as if in a tidal wave.
"We expect a tsunami. There will be a rush. It is their home. If they choose to come back to southern Sudan nobody can prevent them," he said.
'No time to wait'
But the UN's appeals for aid to the south have been hampered by what it calls the "Darfur effect".
The immediate humanitarian crisis of Darfur soaks up emergency funding, and it is hard to persuade some donors to give to other projects in Sudan while the government in Khartoum is held responsible for the continuing violence in Darfur.
Dennis McNamara, the most senior official to visit the region, is responsible for policy on internally displaced people worldwide.
He says that the response of donors now to peacekeeping and nation-building in the south has not matched the very considerable investment in making the peace in the first place.
The UN says it needs $680m (£385m) for southern Sudan. But it has received pledges for less than half of that.
Mr McNamara is sure that it will come eventually, but he says: "We can't wait for two to three years because the people are not going to wait.
"They're coming back to very little or virtually nothing in some cases."