Response of Bolivian Altiplano Lakes to Seasonal and Annual Climate Variations

Abstract: The Bolivian Altiplano is situated between two mountain ranges, the western and eastern central Andes in South America. It has two major lakes, Lake Titicaca to the north, and Lake Poopó to the south, which both are important for the nature as well as for the living conditions on the Altiplano. The two lakes are the remnants of large paleolakes. They are joined by the Desaguadero River. Lake Poopó is a terminal lake. It is very shallow, and has a huge surface area. It has extreme level fluctuations and is highly polluted. These conditions have caused ecological imbalances, endangering the biodiversity of the lake and putting the food security of the inhabitants at risk. In the absence of easily accessible topography for the lake, a simple methodology was designed to determine the bathymetry based on combination of satellite images and lake leveling. The lake hypsographic curve was refined using water balance including also the shallowest parts. The long-term oscillations in Lake Poopó’s water levels follow those of Lake Titicaca. Desaguadero is the main contributor of Lake Poopó, fed mainly by water from Lake Titicaca and the Mauri River, with precipitation and runoff from regional rivers making up the rest. Variation of the lake level over the last 80 years has been extreme. During some periods, the lake has been almost dry, and only in one period has it overflowed. The loss of water from the lake is through evaporation. The annual precipitation is low, with a northeast to southwest gradient. There are five homogeneous precipitation zones, each linked to different precipitation mechanisms and area-specific conditions. The effect of climate change on the Altiplano lakes was studied; a precipitation-runoff model was applied and a lake routing model. Inputs to the models were climate adjusted precipitation and temperature. The first scenario included a temperature rise of 1.6oC and a precipitation increase of 20%, while the second only assumed increased temperature. The first case would give more humidity, with higher levels in Lake Titicaca and more marked influence on Lake Poopó, with its water levels staying close to the spill level. The second case, with no increase in precipitation, would result in Titicaca becoming a terminal lake and Poopó becoming highly intermittent, with long dry periods. Past climate patterns were studied using records on the paleo-historic levels of Titicaca, which in turn rendered information about the historic conditions of Lake Poopó. The current Bi-national Directive Plan for protecting and preserving the Titicaca-Desaguadero-Poopó-Salt Fields does not have a fully integrated focus, as it does not include the Mauri River, which runs through Bolivia, Peru and Chile. There is also a lack of legislation on water usage, fishing, and protection of aquatic ecosystems from pollution. Integrated sustainable management is necessary to ensure the survival of Lake Poopó and that of its inhabitants.