Resolving patterns of groundwater flow by inverse hydrochemical modelling in a semiarid Kalahari basin

Abstract

An inverse hydrochemical mixing cell modelling approach has been used for the assessment of water resources in the Otjozondjupa region at the western fringe of the Kalahari basin, Namibia, The analysis is based on hydrochemical data from 1530 wells in the Omatako basin. Cluster analysis applied to a hydrochemical database was used to define, subdivide and stratify aquifer units where poorly defined aquifer boundaries prohibited a straightforward stratigraphic approach. Based on the hydrochemical definition of aquifer units a quantitative inverse hydrochemical model was formulated. As a result inter-aquifer flows were quantified within a mass balance tolerance of 5% for the entire aquifer system. Significant recharge by floodwater infiltration into sinkholes in the Otavi foreland could be identified and quantified.