Lake Titicaca, a Recorder of Dryness Events in the Amazonian Region

Hydrological balance of Lake Titicaca and its basin (located 10 Bolivia and Peru) was calculated in detail over the past 80 years. During this period, the Lake level has experienced intense variations which are mainly linked to the variation of the summer rainfall. These perturbations may be shown to be related to "EI-Nino Southern Oscillation" (ENSO) events. Moreover the isotopic 16O/18O ratio measured in the Quelccaya ice cap (Thompson, 1990) located in Peru at about one degree north of the Lake is also found to be correlated to the Lake water level. This isotopic signal is linked to the variation of the air mass stability over the amazonian region (Grootes et aI., 1989) and is therefore related to the precipitation level on the Titicaca basin. From these considerations, it is demonstrated that Lake Titicaca behave as a "natural large scale pluviometer" for its capacity of recording occurence of wet and dry episodes in the amazonian region.