Valeria, the toddler behind the picture that shocked the world

Her little body was found on Monday, on the grassy bank of the silty, grey-green Rio Grande river which separates Mexico and the United States.

Valeria had one arm wrapped around the neck of her drowned father, Óscar Alberto Martínez. Her head was buried inside his black shirt. She must have, said those who the scene, clung to him in her final moments.

Usually the 23-month-old would just be another statistic. Some 283 migrants - mostly Latinos fleeing poverty and endemic violence in Central America - died crossing in to America last year.

WARNING: THIS STORY CONTAINS UPSETTING IMAGES

But Valeria was different. Somebody, a journalist, Julia Le Duc, took her picture and then published it on the front page of her newspaper, Mexico's La Jornada, under the headline "Died in their Dream".

And so Valeria's image - shared on social media - snapped America out of its ignorance of the horrors on its frontier. You can ignore numbers, not pictures.

"The photo of the drowned migrant father and toddler broke me," tweeted New York journalist Maggie Serota.

The picture

This, declared social media users, was America's Alan Kurdi moment. Back in 2015 the enormity of the tide of humans fleeing the war in Syria was summed up by a picture of three year old Kurd Alan Kurdi, his heartbreaking, rag-doll-like remains washed up a Greek holiday beach.

America for weeks has been debating the rights and wrongs of detention centres - 'concentration camps" said one congresswoman - for migrants on its southern frontier.

Donald Trump - who has called Mexicans 'rapists' - has ramped up rhetoric of a 'crisis' on the border. And he was half right, suggest aid groups: there is a crisis, a humanitarian one.

So how did Valeria end her short life in the dirty water of the Rio Grande? Ms La Duc explains.

Mr Martínez, his wife Tania Vanessa Ávalos and little Valeria had made their way to Matamoros, the border town near Brownsville, Texas.

They were from El Salvador, a country where Amnesty International warns of "grave human rights abuses" and whose criminal gangs, such as MS-13, have become an essential part of anti-migrant sloganeering by Mr Trump.

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 The family, according to Ms Le Duc in La Jornada, had had been waiting for an appointment to make an asylum application for two months. Mr Martínez, tired of the wait to see asylum officials in a migrant camp near the border, decided to risk crossing across the Rio Grande.

So he swam across the river on Sunday with his daughter. He made it. He set the child on the U.S. bank of the river and started back for Ms Ávalos.

But, frightened to see him swim away, Valeria threw herself into the waters. Mr Martínez returned and was able to grab Valeria, but the current swept them away. Ms Ávalos stayed on the Mexican side. She saw her family submerge and desperately tried to get Mexican authorities to help. It was to take 12 hours to find them, washed up half a kilometre from where were last seen.

Later Ávalos was to tell both Ms Le Duc and her mother-in-law back in El Salvador, Rosa Ramírez, the whole story.

“When the girl jumped in is when he tried to reach her, but when he tried to grab the girl, he went in further ... and he couldn’t get out,” Ms Ramírez told the AP news agency. “He put her in his shirt, and I imagine he told himself, ‘I’ve come this far’ and decided to go with her.”

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The Herald's sister paper, USA Today, said details of the incident were confirmed on Tuesday by a Mexican provincial government official who was not authorized to discuss the matter publicly and spoke on condition of anonymity.

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Why did Mr Martínez decide to take such a risk? Ms Le Duc in La Jornada explained. Until recently there were two camps for migrants near Matamoros, at Puente Viejo and Puerta México. They were full of Salvadorans, Nicaraguans, Brazilians and Africans hoping to get an interview for asylum.

Camley's cartoon

Ms Le Duc reported: "At the end of May the number of applications was around 2,000 and there was a multitude of foreigners a multitude circling Puente Viejo y Puerta México where US agents give an average of three appointments a week."

One of the camps, Puente Viejo, has now been dismantled. That means everybody has headed to the other. Ms Le Duc reported: "In conditions of hunger and overgrowing, and amid temperatures of up to 45 degrees, migrants wait for an opportunity to be heard , to get a better quality of life."

Syrian Kurd Alan Kurdi is found on a beach

Mr Martínez and Valeria did not die alone this week. Elsewhere in Texas four Guatemalans succumbed to heat and dehydration.

Two babies, a toddler and a woman were found dead on Sunday, overcome by the sweltering heat; elsewhere three children and an adult from Honduras died in April after their raft capsized on the Rio Grande; and a six-year-old from India was found dead earlier this month in Arizona, where temperatures routinely soar well above 100 degrees Fahrenheit.

"Very regrettable that this would happen,” Mexican President Andres Manuel Lopez Obrador said Tuesday in response to a question about the picture of Valeria. “We have always said that as there is more rejection in the United States, there are people who will lose their lives in the desert or crossing."

There was no immediate comment from the White House, said USA Today.