Urban population boom threatens Lake Titicaca

Aymara women cross a bridge of rocks on the shores of Lake Titicaca. The lake's water is increasingly contaminated by rivers that pass through the industrial city of El Alto. Photograph: Noah Friedman-Rudovsky

South America's most famous lake is being polluted by increasing levels of waste from fast-growing cities, according to locals, environmentalists and politicians.

Lake Titicaca, which sits on the border of Bolivia and Peru, has sustained agricultural societies on the dry, high-altitude Andean plains for thousands of years, but is now threatened by a population boom from nearby cities and towns.

El Alto has grown at 4% a year for two decades as rural peasants seek a better life, and is now the country's second largest city and the largest urban centre in the Titicaca watershed.

But this migration has had devastating effects on the rivers of El Alto, communities downstream and Lake Titicaca. Raw sewage, garbage and industrial waste are all dumped into the Seco River, which flows through the heart of El Alto. At the edge of the city, where the Seco begins a 40-mile journey toward Lake Titicaca, it also receives treated wastewater from the city's severely overtaxed treatment plant. Those waters mix and travel out over the flat plains.

Because of its size and history, El Alto is a political powerhouse, yet the chronic poverty and lack of access to services widely faced by Bolivia's indigenous peoples persist there, and tackling pollution is a struggle. Changing the waste disposal habits of the sparsely populated countryside is one obstacle. But at the heart of the matter is weak enforcement of environmental laws and inadequate infrastructure.

"There is no complete and structured treatment of wastewater," said Marco Ribera Arismendi of the Environmental Defense League in La Paz. "The things governments have done so far are like giving an aspirin to someone who has been shot."

Edgar Patana Ticona, El Alto's mayor, says trying to enforce environmental standards in the city is a tough task. "If we monitor a specific business then the people who work there, the owner and all the neighbours begin to protest," he said. "And not so that we enforce the rules - but so the business can continue operating."

El Alto's budget depends on Bolivia's central government, and collects little from local taxes. A constantly expanding network brings drinking water to about 80% of the city's homes, and international funds are helping install more sewers – but the construction of a new plant to treat more wastewater is, at best, years away.