| On a historical time scale, this paper investigates the effect of hydroclimatic
variations on the surface water salinity of Lake Tanganyika, the largest African lake and
an open freshwater reservoir. Through annual water and chemical budgets, based on original
and bibliographic data, a tracer of the water regime is proposed. Chloride, an inert and
conservative element, seems to be the best candidate although its contribution to salinity
is small; its use as a tracer of the water regime is validated on seasonal and historical
time scales. Seasonally, a monthly water and chloride budget, constructed for an average
year has been compared with data acquired in 1973. On a historical time scale, bibliographic
data of chloride concentrations, compiled since 1939 have been compared with the level
variation curve. The relation between lake level and surface water chloride concentration
is significant on both time scales. Hence, the surface salinity/chlorinity of this
freshwater lake is sensitive to hydroclimatic variations even if level variations are very
limited in comparison with its great depth. This sensitivity is due mainly to the permanent
thermo-haline stratification of the lake.
Keywords: climate, water budget, hydrochemical budget, Lake Tanganyika, limnology, salinity |