New Zealand hiker Claire Nelson's incredible story of survival in Joshua Tree National Park, in the Californian, US, desert

Claire Nelson lay in agony for about 72 hours in a US desert with a shattered pelvis. Photo / Supplied

A New Zealand expat who survived three days trapped in the unforgiving heat of a US desert, unable to move after a fall that "shattered" her pelvis bone, has shared her incredible survival story with the Herald.

Lying alone in a national park in California, Claire Nelson was in disbelief at the situation she found herself in but thought there was "no sense in panicking".

She had veered off the Lost Palms Oasis track in the Joshua Tree National Park and was traversing over rocky terrain when she slipped about 30 to 40 feet, breaking her pelvis bone.

"I heard the crack," Nelson told the Herald.

"I was in agony."

People should never think they are smarter than Mother Nature.

Claire Nelson

She tried to call emergency services but had no cellphone reception and endured three days alone before rescue.

"I made a foolish mistake not telling anyone what my plans were."

Nelson was forced to drink her own urine to fight dehydration and used a walking stick to apply sunscreen to her legs in a bid to prevent the worst of the burns.

People did not know how truly determined they could be until put in a situation like that, she said.

"It was hard because the heat is enough to kill you."

Joshua Tree National Park where Claire Nelson was rescued after veering off the Lost Palms Oasis Trail. Photo / Supplied

When nightfall came she was terrified of what lay in the dark, fearful of being attacked by snakes.

But she was determined to see her family and friends again - determined to spare them the pain of learning she had died in the desert.

Due to meet a friend on Thursday, Nelson had pinned her hopes on rescuers coming when she did not show but as time wore on started to feel despondent.

"My hope was fading ... this is the end."

Then she saw the rescue helicopter in the sky and knew it was her last chance.

"This is it ... I have to make sure they notice me."

She managed to signal the crew by frantically waving a T-shirt and hat tied to a stick.

Speaking from the Desert Regional Medical Centre this morning, Nelson said what happened to her was a cautionary tale.

"People should never think they are smarter than Mother Nature."

She said an X-ray confirmed she had "shattered" her pelvis bone.

Rehabilitation would take time, but she was "so happy to be alive".

"I feel so lucky."

The reaction from friends and family had been incredible and drove home how insane the situation was, she said.

Nelson is a freelance writer who grew up between Auckland and Wellington.

She left New Zealand in about 2005 to spend time largely in London and Canada.

Claire Nelson poses with a husky dog while sledding in Canada. Photo / Supplied