The river was not very far. Chaz Powell could see the Zambezi just a few hundred yards down the gorge. It was tantalizingly close, but out of reach.
“I can’t describe how thirsty I was,” says Powell.
Had run out of water and had no way to go down to the river. “I was starting to feel really bad,” he says. “My body temperature was crazy.”
Powell, UK expedition guide, was about to experience what it’s like to be stranded without the comfort that most of us take for granted.
In most developed countries, accessing safe water is as simple as turning on a tap.
But around 1.1 billion people lack access to safe water worldwide, and a total of 2.700 million have difficulty obtaining it for at least one month of the year.
And when we run out of water, things can get ugly very quickly.
Powell experienced this on a solitary expedition along the Zambezi River in Africa, having started his journey in Zambia.
It was August 2016, the hottest time of the year, with temperatures reaching 50 ° C during the day.
Powell, who was then 38 years old, had to walk to avoid the Barotse floodplains, which were submerged 90% of the time.
It was going well. He had managed to travel an average of 36 kilometers a day.
But once in the Zambezi River Gorge, Powell slowed considerably. “I started doing no more than two miles a day,” he recalls.
At such a slow pace, Powell calculated that it would take him a month to reach the other end of the gorge, and he was starting to run out of food.
So I needed to find another route.
One day at four in the morning, Powell started out of the gorge with two two-liter bottles of Zambezi water.
When he started walking, the temperature was already 48 ° C. Three hours later he managed to get out of the gorge, after climbing between 750 meters and a kilometer. Until then, he had one bottle of water left.
But when he reached the top, the terrain was not what he expected.
“It was completely covered in thorns and it was just a series of little hills that went down into the gorge,” says Powell. After three hours of walking, he ran out of water completely.
“So I decided that I was going to try to go back down,” he says. But he was no longer in the same place he had climbed and there was no way to descend.
Onset of dehydration
On average, water makes up about 60-70% of the human body.
Our body loses water through urine, sweat, feces and breath, so we have to continually replace it. If we don’t, we can become dehydrated.
The first stage of dehydration is thirst, which is activated when 2% of body weight is lost.
“The body holds on to all the remaining moisture,” says Dileep Lobo, professor of gastrointestinal surgery at the University of Nottingham, UK, who researches fluid and electrolyte balance.
“To maintain oxygen levels, your heart rate increases,” he adds.
The rate at which dehydration occurs varies depending on the conditions the body is subjected to.
“Human beings have a limit of tolerance for heat. When we get over it, we suffer heat stress and even death, ”says Lobo.
“Mortality rates increase on extremely cold days, but increase much more on extremely hot days.”
Even mild dehydration can make us feel more tired and less able to function physically.
As we lose more water our ability to cool ourselves through sweat also decreases, which increases the risk of overheating.
Our blood begins to thicken and become more concentrated, which means that our cardiovascular system has to work harder to keep our blood pressure high.
Our kidneys try to compensate for dehydration by retaining more water through reducing urination.
Water also leaves our cells into the bloodstream, causing them to shrink.
After effects of dehydration
By losing 4% of our body weight in the form of water, blood pressure decreases and fainting can occur.
When 7% of body weight is lost, organic damage occurs.
“Your body has trouble maintaining blood pressure,” says Lobo.
“To survive, it slows blood flow to non-vital organs, such as the kidneys and the intestine, causing damage to them. Without the kidneys filtering the blood, cellular waste accumulates rapidly.
However, some people can survive such severe dehydration and may even continue to perform at high levels.
Powell activated an SOS phone he carried that was linked to a service operated by a US-based company.
But when they answered him, they didn’t find anyone nearby who could help him.
Desperate, Powell dug a hole in the dry dirt to keep cool and began to drink his own urine, which he combined with a sachet of rehydration salts.
In a healthy adult, urine is 95% water and the rest are waste products, excreted by the kidneys, including salts and ammonia.
When someone is dehydrated, the water content drops dramatically, which makes drinking urine more like drinking seawater.
“Although it may be safe to drink urine in the short term to rehydrate, the physiological response to dehydration is to conserve salt and water,” says Lobo.
“Urine production decreases and, ultimately, humans can develop acute kidney injury and anuria (the kidneys do not produce urine). Therefore, the amount of urine in the medium term will not be sufficient to maintain adequate hydration ”.
Adding rehydration salts without a good amount of water could help Powell replace the salts and sugar, but it also ran the risk of causing more imbalances in his body.
In extreme cases, an imbalance in salt levels can lead to seizures and even brain hemorrhage.
Going down the cliff
Eventually, an SOS team told Powell that they could get him a helicopter, but that it would take four hours.
I’d rather die falling off a cliff than sit here, he thought.
He scanned the cliff and saw some exposed tree roots to hold onto, so he decided to go down. But he fell several meters and cut his nose.
His decision to go down may have been due in part to dehydration itself.
As dehydration worsens, it can affect how our brains work, altering our mood and our ability to think clearly.
Blood flow to our brain, and the volume of the brain itself, is reduced.
Mild to moderate levels of dehydration (a loss of 2% or more of body water) can affect our short-term memory, our surveillance, arithmetic capacity and coordination skills, particularly when doing strenuous activities in hot environments.
Some studies, mainly in elderly patients, have also found that dehydration can play a role in delirium.
However, Powell kept going down and pushed himself off the cliff for almost an hour until he managed to get back to the river.
He had to sit there for an hour, cooling off and drinking water, until he was able to access his satellite phone to tell his rescuers that he was fine.
“Dehydration is reversible, and by replacing body water you are likely to make a full recovery,” says Natalie Cookson, an ER doctor trainee working in London.
If he hadn’t managed to rehydrate, Powell’s kidneys would have started to fail.
Toxins can start to build up, causing the kidneys to stop working properly.
This can lead to a form of kidney damage known as acute tubular necrosis, which even if rehydration occurs, can take weeks to reverse.
The added stress on his heart would also have led to an irregular heartbeat, a drop in blood pressure, and possibly seizures.
Dehydration can also cause vital parts of the cardiovascular system, such as blood vessels, to harden, increasing the risk of a heart attack.
Being dehydrated in hot weather only compounds the problem.
“The body is unable to regulate heat, which causes the destruction of key enzymes in normal metabolic pathways, causing organs like the brain, heart and lungs to stop working,” says Cookson.
Eventually, this can lead to seizures, coma, and, when organs begin to fail, death.
Time without water
How long exactly can someone survive without water is still largely debated. Most scientists agree that humans can only go a few days without food or water.
In 1944, two scientists were deprived of water, one for three days and one for four days, but they ate a dry diet.
By the last day of their experiment, both had difficulty swallowing and their faces had turned “somewhat pale.”
But they stopped the experiment long before her condition deteriorated to the point of becoming dangerous.
The capacity of stay without water can also vary greatly from person to person.
There is some evidence, for example, that the human body can adapt to the level of water that is consumed regularly.
The longest known time that someone has been without water was in the case of Andreas Mihavecz, an 18-year-old Austrian bricklayer who was locked in a police cell for 18 days in 1979 after duty officers forgot of the.
His case even made it to the Guinness Book of Records.
While few of us likely experience this type of extreme dehydration, around 4 billion people experience severe water shortages at least one month out of the year.
Climate change is also likely to hamper access to safe water supplies in many parts of the world.
By some estimates, up to two-thirds of the world’s population will face water shortages by 2025.
Although Powell’s experience was a lesson in patience, it also taught him how important water is.
“I certainly don’t take it for granted anymore,” he says.
Remember that you can receive notifications from BBC Mundo. Downloadto our app and activate them so you don’t miss our best content.