An integrated approach for understanding natural -and anthropogenic controls on water quality in arid and semi-arid environments

The objective of this review is to highlight the need for an integrated approach to the understanding of the major processes controlling the hydrochemical composition of water bodies in drylands using multivariate statistics, water quality index and heavy metal pollution index. The integrated approach to the hydrochemical investigation of streams and aquifers in drylands is essential owing to their distinctive climate, notably, low rainfall and high temperature. Studies on water quality in arid and semi-arid areas using multivariate analysis and water quality indices were scrutinized. Results showed that the hydrochemistry of streams and aquifers is controlled by both the natural geogenic processes and anthropogenic activities. However, in-depth understanding of geochemistry and land use types, as well as climatic vagaries, is required, to be able to discriminate these processes, since several ions of rock minerals origin are increasingly being added into the environment through human activities. While the sources of solutes and processes controlling the hydrochemistry of streams and aquifers can be established through application of multivariate analysis, this technique is limited in water quality investigations since it cannot measure the suitability of water for domestic, agriculture and industrial uses. Thus, an integrated approach incorporating water quality indices in conjunction with multivariate analysis is required. This is essential owing to the fact that the suitability of water for various uses is central to any hydrogeochemical investigation in arid and semi-arid environments. Thus, it is expected that future hydrochemical studies would apply this approach.