“I had walked maybe a couple of miles a day, if that, just going over boulders,” he says.

But once in the gorges, Powell found himself slowing considerably. His trek had been going well, covering around 20 miles (36km) each day. Powell, who was 38 at the time, had to walk at this time of the year to avoid the Barotse Floodplains, which are under water for about 90% of the time. It was August 2016, and the hottest time of year, with temperatures reaching 50C (122F) during the day. “The gorges are steep sloped cliffs that carve through the landscape for around 150 miles,” Powell says. Here, the terrain became much more difficult to traverse. He followed the river through eastern Angola, across the borders of Namibia and Botswana, until he reached the gorges at the border of Zambia and Zimbabwe, after Victoria Falls.

Powell experienced this for himself while two months into a solo expedition walking the length of the Zambezi River, having started his trip at its source in Zambia. When we are forced to go without water, things can turn nasty very fast indeed. Water is one of the fundamental ingredients for life on Earth and our bodies are mainly composed of it. But around 1.1 billion people lack access to safe drinking water around the world, and a total of 2.7 billion find water difficult to access for at least one month of the year. People in these places pour gallons of it down the drain every day without a thought, as they brush their teeth, shower and flush the toilet. In most developed countries, accessing clean water is as simple as turning on a tap. Powell, an expedition guide from Shropshire in the UK, was about to experience what it is like to be stranded without the commodity most of us take for granted. “I started to overheat, and my body temperature was just insane.” “By this point I was starting to feel really ill,” he says. Recalling the precarious position he found himself in, Powell describes an overwhelming feeling of panic as he worried about how to find something to drink. Teetering on the edge of a cliff at the top of a gorge, he had run out of water and had no way of getting down to the river. “I can't describe how thirsty I was,” says Powell. It was tantalisingly close, but out of his reach.

Chaz Powell could see the Zambezi churning over boulders in the gorge a few hundred metres below him.

7 days to die food and water hud