Lake Titicaca, the highest navigable lake in the world has a weird foam layer on the surface and emits a smell of decay.

Puno, Peru – Taking a boat from the pier of Puno into Lake Titicaca, the highest navigable lake in the world, means moving through murky water full of floating plastic first. Along the shores of the lake that lies on the border of Bolivia and Peru, the water has a weird foam layer on the surface and emits a smell of decay.

The famous floating islands of the Uros tribe lie only a few kilometres off the bay of Puno. They are a native tribe in Peru who live on islands made of reed. Joel Porcela, 57, lives with his family on one such island.

His wife lays out the fresh catch of silverside fish on a blanket to dry under the shining sun, while his daughter is in the back cutting the reed. The Uros not only use this plant for their floating islands, they also build their houses and boats from it, and use it as fuel for cooking. It’s a way of life that has existed for generations.

Everything they need basically comes from the lake: the reed, the fish they eat, the water they drink and the contamination of the lake, which is advancing from the shores towards the islands, is a threat to their lifestyle.

“I think the water is still clean where we are,” says Porcela. “But, if we are drinking contaminated water, we probably have already become resistant. Either way, this is how we have always lived, so we cannot change that.”

This contamination is clearly connected to the cities surrounding the lake.

Puno for instance, grew out to become a city of 120,000 people, while its sewage systems can cope with only a third of that number. But not all contamination is as visible: in the Ramis river, a tributary that feeds into the lake on the northwest side, high levels of mercury have been found in the sediment, which probably stem from wildcat gold mining in the area.

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Decontamination plans

Lake Titicaca spans a big area, with a maximum length of 190km and a width of 80km.

Engineer Alfredo Mamani Salinas, who works for the Autoridad Binacional del Lago Titicaca, a bi-national organisation that monitors the lake, says they are still in the process of assessing how contaminated the lake is.

“Contamination is mostly concentrated on some points where rivers enter the lake, after which it is diluted,” says Salinas.

Last November, the Peruvian President Pedro Pablo Kuczynski, who took office on July 2016, agreed with Bolivian President Evo Morales to start with the first part of a huge $500m plan to clean up the lake.

This first step, with an estimated cost of $63m, would consist of constructing 10 water treatment facilities to make sure the water entering the lake is clean of industrial waste and sewage water.

According to Salinas, just building plants is not enough to tackle the problem. “It is important to start with cleaning the water and the sediment in the lake along with treating the water of the rivers. The contamination is already in the lake, so we have to take that out to have a positive effect.”

But, the promise of building treatment facilities works a signal of hope for the Uros.

Porcela says he believes the new Peruvian president will do a good job in cleaning the lake.

“Kuczynski grew up in this area,” tells Porcela, while he looks out over the water, referring to the part of his youth that President Kuczynski spent in Puno. “He understands the problems we have here.”

According to Porcela, before Kuczynski, the only president who was interested in the fate of the Uros was Alberto Fujimori, the dictator who reigned the country in the 90s and who is currently serving a 25-year prison term for corruption and crimes against humanity. Fujimori had visited the lake.

There are still solar panels on the floating islands that were built by the Fujimori government, giving the Uros something to remember this president by.

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Every few days, the Uros take their rubbish to Puno, where it is processed [Eline van Nes/Al Jazeera]

Dead frogs

Along the boulevard of Puno on a small patch of land, 32-year-old Edgar has his sheep graze on the grass. His father and grandfather were also sheep herders. But back in those days, it was a lot cleaner here.

Now Edgar’s sheep walk through dark mud full of plastic waste.

“During the rainy season, a lot of waste is flushed into the lake, cleaning up the shores a bit,” he says. “But you can’t drink the water from the rivers any more, as my father and grandfather used to do.”

The lake is still liveable now, but the contamination keeps coming. Victor Hugo Apaza, Engineer

Last October, thousands of frogs were found dead along the shores near the River Coata, which is a tributary to the lake on the northern Peruvian side.

The frog, named a scrotum frog for its baggy skin that allows it to take in enough oxygen at a high altitude, is a critically endangered species found only in Lake Titicaca.

According to engineer Victor Hugo Apaza Vargas, who oversees a part of the national reserve in Lake Titicaca for the Peruvian Ministry of Environment, an official reason for the death of the frogs has never been given because the samples didn’t reach the laboratory in Lima on time.

“But it is reasonable to assume it had to do with pollution,” he says in his office in Puno. “There was cleaning going on in the canals of the city of Juliaca, upstream. So, we can easily conclude polluted sediment had reached the frogs’ territory.”

According to Apaza, a similar incident happened in 2013, when a lot of dead fish were found in the bay of Puno. They had died of asphyxiation, which, according to the engineer of the ministry, was a result of a combination of a high influx of sewage water during the holiday season when many tourists visit the town and an abnormal high temperature that month.

Apaza explains how the reeds, around the floating islands of the Uros, are a natural barrier for contamination.

This way the contamination doesn’t enter the area where the islands are, but the quality of the reed on the edges of the islands has deteriorated: both Uros and people living on the shores of the lake, who use the reed as fodder for their animals, have complained about this to the Ministry of Environment.

“The lake is still liveable now,” Apaza says. “But the contamination keeps coming. We have to do something about this fast, otherwise there will be huge problems here in the future.”

Ever since the engineer started his job in Puno five years ago, he has heard complaints and seen incidental protests by villagers. He sent requests to the head office in Lima often, but the reaction has been slow, so he is glad finally that there is bi-national consensus on how to start cleaning up the lake.

READ MORE: Bolivian women mining for a living and for respect

Sheep herder Edgar walks with his sheep on a small patch of grass by the boulevard of Puno. It’s hard for the sheep to find any juicy grass to eat among the waste [Eline van Nes/Al Jazeera]

Drought

Besides contamination, the lake might have another problem to face. In November 2015, neighbouring Lake Poopo in Bolivia dried out.

Johnny Terazas Garcia, working for the research institute CEPA in Bolivia, says this happened due to the clogging up of the rivers feeding into the lake from mining wastewater in combination with global warming – between 1995 and 2005 the temperature around the lake had risen by 0.9 degrees Celsius.

What is left of Lake Poopo now is only a salt flat, comparable with the Salar de Uyuni, in Bolivia. Fishermen have moved away from the area to find other work.

Just like Poopo, Lake Titicaca is also shrinking: the surface is on average already a metre lower than before, according to biologist Jose Luis Vilca Ticona, working for the Lake Titicaca Special Project, PELT.

Satellite photographs clearly show this difference.

“This is a strong preoccupation for us,” says Vilca. “Although we have to note this still might change for the better. There is always fluctuation in the lake’s surface. But we are going through a year where it is very low.”

Meanwhile, for the Uros life goes on as usual.

Every day they take boats full of tourists to their islands, where they tell a story about their traditions. Normally they don’t mention the contamination and their worries about the lake to visitors. But when a tourist throws an empty plastic soda-bottle in the water, Porcela gets angry at him.

After the tourists have left his boat, he says: “Without tourism these islands probably wouldn’t have existed any more. But, they have to respect our lake.”