In December 2015, while the world’s eyes were on the UN Climate Conference in Paris, Bolivia’s Lake Poopó—once the country’s second-largest lake, with an area of 2700 square kilometers–dried up completely. This event was first recognized by the regional government, located in Oruro, and soon drew national and international concern. This attention has opened a discussion on the causes of this event and on the troubling possibility that the lake may never return to its earlier size.
Some people, like Bolivian President Evo Morales, were quick to attribute the drying of Lake Poopó to natural cycles, pointing out that the lake had previously dried out, but always recovered. But others claim that climate change has played a role that will continue into the future, and also note the negative impact of human activities–irrigation schemes and mining activities–which are very unlikely to end.
Based on available documentation and a field visit earlier this month, we are now in a position to share some preliminary conclusions on what happened to Lake Poopó, as well as to the perspectives for its recovery.
The current sharp decline is due most immediately to the strong El Niño event of 2015-16, which has greatly reduced rainfall in the November-March wet season, now reaching its final weeks. But the problem is rooted in long-term processes, which will not be reversed when the current El Niño event ends, most likely later this year.
The Physical Environment of Lake Poopó
Lake Poopó, like all other lakes, can be characterized by what limnologists–fresh-water ecologists–call a “water balance,” the relation between the water that enters the lake, and the water that leaves it. If unimpeded, a negative water balance will lead to the drying up of a lake. The water balance of Lake Poopó is influenced by its location in a semi-arid area (the average annual precipitation is about 370 mm) and its shallowness (the greatest depth is only 2.4 m).
Historically, Lake Poopó receives around two thirds of its water from a sole source, the Río Desaguadero; the remaining third comes from smaller rivers that flow directly into the lake and from rainfall onto the lake’s surface. The Río Desaguadero originates in Lake Titicaca, a large lake that straddles the border between Bolivia and Peru. As this river flows towards Poopó, it receives water from other tributaries, particularly the Río Mauri, an international river whose sources lie in Peru and Chile. Lake Titicaca and the other tributaries of Río Desaguadero receive water from rainfall, snowmelt and runoff from the glaciers on the cordilleras that ring the entire Titicaca-Poopó basin.
These sources provide Lake Poopó with water inputs that fluctuate from year to year, reflecting variations in the precipitation that the region receives. A set of locks that were constructed on Lake Titicaca in 2001 could permit the Binational Commission charged with managing the lake to release more water to the Río Desaguadero in dry years, but this possibility has never been realized and, given the water scarcity on the Peruvian side of the Titicaca basin, it seems very unlikely.
Local residents report a decrease in rainfall over the last 10-15 years, a pattern that is confirmed by data from weather stations for the last few decades and by tree-ring records that track rainfall over several centuries. Moreover, glacier retreat has diminished the contribution of meltwater to the lake–a valuable component of the water budget, since it historically compensated in part for the scanty rainfall in dry years. Bolivia has lost about half of its glacier area in the last 40 years, with particularly rapid retreat in the eastern portions of the Titicaca-Poopó basin, where the largest glaciers are located.
Moreover, climate change affects another component of the lake’s water budget: its losses. Higher temperatures lead directly to higher evaporation rates, a significant effect in this extremely shallow body of water.
Human Activities Impact Lake Poopó
In addition to these physical factors, human activities have reduced the water input into the lake. These activities begin far away, since new irrigation facilities draw from rivers on the Peruvian side of the basin, diverting water away from it.
In the last 10 years, new irrigation systems for small farmers have been built closer to the lake as well. During our trip around and onto Lake Poopó, we saw a large number of canals, many of them of makeshift construction, which divert water from the Río Desaguadero for agricultural purposes. According to Eduardo Ortíz, the Oruro regional government’s director for watershed management, there are around 250 irrigation schemes legally established on the Río Desaguadero. Other experts estimate that the total number of irrigation projects is closer to 1,000, suggesting that many of them lack legal authorization. Further down its course, the Río Desaguadero was entirely dry. When we came to the former shores of the lake, we found many small villages half-abandoned, especially on the western side of the lake. The final concern is the deterioration of water quality in the lake because of contamination from nearby mines at Huanuni and other site. Salts containing lead, cadmium, arsenic and other heavy metals leach into the lake. Local communities have protested this pollution in recent years. These toxic substances become concentrated in periods of low lake levels, and could affect the restoration of lake ecosystems even in years of heavier rainfall.
The drying of the lake has led hundreds of fishermen to lose their source of income, accelerating migration by the local population to urban areas. Antenor Rojas Flores, a local fisherman from the village of Untavi in his late 50s, has begun to work as a laborer in construction in the nearby city of Oruro to support his family. He says that he hopes that water and fish will return, so that he can go back to his life as it was before, but “only God knows” whether that will happen.
The decline of fishing has also impacted the commercial activities of women, many of whom have participated in local and regional markets. These people are members of the indigenous Uru Murato, an ethnic group with ancient roots in the region. Their livelihoods have always centered on the water, and the drying of the lake is threatening their continuity as a community; the barter relations with neighboring agricultural and pastoral communities, which supported them during dry spells in earlier historical periods, have weakened as these communities also face climate change and other pressures.
Worrying Perspectives for Lake Poopó
This set of circumstances leads to a bleak outlook for the lake. Its full recovery seems rather unlikely. The strong El Niño event of 1991-92, followed by a weaker event in 1994-95, led the lake to dry up as well; in the decades since then, it recovered neither its full size nor its full potential in terms of productivity and biodiversity. Historic lake sizes ranged between 2,500 and 2,700 square kilometers; for the current century it has been closer to 1,500 square kilometers, reflecting the impacts of climate change on evaporation and on glacier retreat. The irrigation facilities are likely to continue to divert water. It would take strong political will to reallocate water extensively throughout the international Titicaca-Poopó basin to bring the lake back to even a semblance of its state in the last century.
Dirk Hoffmann is a researcher with the La Paz based Bolivian Mountain Institute – BMI and can be contacted at: email@example.com