Geographical patterns, and their origins, in the dominance of major ions in South African rivers

Abstract

The proportions of ions in rivers of South Africa and Lesotho were investigated using Maucha diagrams, which allow a visual assessment of the ionic proportions of any water sample. Four broad categories of ionic proportions show clear geographical distribution patterns. Linked to the geological and climatological character of the country. Waters in categories I and 2 are 'rock dominated'; dilute waters in category 4 are 'precipitation (rainfall) dominated' and concentrated waters in category 4 are 'evaporation-precipitation (crystallization) dominated'. It is shown that dilute rainfall-dominated waters can become directLy evaporation-dominated in more arid areas.