Lake — Groundwater Relationships, Oxygen Isotope Balance and Climate Sensitivity of the Bishoftu Crater Lakes, Ethiopia

Oxygen isotope data from groundwater, streams and crater lakes in central Ethiopia provide a basis for modelling lake hydrological and isotopic budgets. The environmental parameters δ_A(isotopic composition of vapor) and ε* (equilibrium fractionation factor) were determined by a semi-empirical approach using one lake as a terminal index lake. The models show that lake oxygen-isotope composition is more sensitive to rainfall-related parameters (humidity and δ_A) than to the isotopic composition of inflow (δ_in). The isotopic composition of the lacustrine sedimentary carbonates should therefore provide a record of past rainfall variation.