AbstractA few of Tasmania's several thousand lakes and rivers have been sampled in a preliminary survey of water chemistry. They range in concentration from extremely dilute glacial lakes (TDS85%), the majority being dilute (TDS<50 ppm). The 3 mechanisms controlling water chemistry proposed by GIBBS (1970) are seen to operate and the 3 terminal water types showing precipitation‐dominance, rock‐dominance and solubility‐limited composition are found, together with a range of intermediates. The majority of waters have seawater ionic composition or moderate geochemical modification of