Svold left Whanganui on July 8, after spending a month here. He timed it to take in Puanga, the Māori New Year celebrations.
Soon after arriving he was up on Mount Ruapehu for Puanga Mountain Karakia. Days later he was at Putiki slipway, for Puanga River Karakia.
With the help of Mike Poa, Gail Imhoff and Chevron Hasset he was introduced to everyday life and important events on the river.
He canoed it, spent a few days at Blue Duck Station in the mid reaches, flew over it in a helicopter.
He wanted to meet people for whom the river was more than just running water, available to be used in various ways. That's the western view, he said, in which nature and people are two different things.
The Whanganui River whakataukī (saying) "I am the river and the river is me" is the opposite. He's hoping the river story will provoke some changes.
"I want to challenge the western way of thinking and inspire people to reflect about the value of their own nature they have at home."
The "legal personhood" concept may not be a total solution, but it will have symbolic value, he said.
"It's only the beginning of a new journey for the people here but I think it can inspire people everywhere to reflect about their own values."
Headlines he saw in Europe after the Te Awa Tupua (Whanganui River Claims Settlement) Bill became law in March last year were focused on how unusual it was to make a river a legal entity.
"I think it only made the headline as a spectacular story. I couldn't find articles that said what it meant."
He came looking for "a community of people who have a strong relationship with the river" - and he found it.
He then looked at what happens on the river, including water sport and canoe journeys.
"It's not a Māori story about Māori traditions and culture. It's more general."
Svold uses old-style medium-format film for his photographs. He also recorded conversations and took video. He now returns to Washington DC to show what he got.
A writer will be chosen for the story - probably a New Zealander - and Svold may return in summer to get more photos. It could be another year before the story appears.
The story will be well read. National Geographic magazine is 130 years old and 7 million copies a month are published. They're translated into about 40 languages and read by about 60 million people.
At home in Denmark, Svold is a photographer taking studio photographs for businesses and freelance photographs for newspapers. He also has his own personal projects, mainly using documentary photography.
Two of them are about how Danish people relate to nature - their coastline and their forests. They can be seen on his website, http://www.mathiassvold.dk.
