The assessment of processes controlling the spatial distribution of hydrogeochemical groundwater types in Mali using multivariate statistics

• Published in: Journal of African earth sciences (1994) 2017-10, Vol.134, p.573-589
• Main Authors: Keita, Souleymane, Zhonghua, Tang
• Format: Article
• Language: English
• Subjects: Cluster analysis; Groundwater types; Hydrogeochemistry; Mali
• ISSN: 1464-343X; 1879-1956
• DOI: 10.1016/j.jafrearsci.2017.07.023

Sustainable management of groundwater resources is a major issue for developing countries, especially in Mali. The multiple uses of groundwater led countries to promote sound management policies for sustainable use of the groundwater resources. For this reason, each country needs data enabling it to monitor and predict the changes of the resources. Also given the importance of groundwater quality changes often marked by the recurrence of droughts; the potential impacts of regional and geological setting of groundwater resources requires careful study. Unfortunately, recent decades have seen a considerable reduction of national capacities to ensure the hydrogeological monitoring and production of qualit data for decision making. The purpose of this work is to use the groundwater data and translate into useful information that can improve water resources management capacity in Mali. In this paper, we used groundwater analytical data from accredited, laboratories in Mali to carry out a national scale assessment of the groundwater types and their distribution. We, adapted multivariate statistical methods to classify 2035 groundwater samples into seven main groundwater types and built a national scale map from the results. We used a two-level K-mean clustering technique to examine the hydro-geochemical records as percentages of the total concentrations of major ions, namely sodium (Na), magnesium (Mg), calcium (Ca), chloride (Cl), bicarbonate (HCO3), and sulphate (SO4). The first step of clustering formed 20 groups, and these groups were then re-clustered to produce the final seven groundwater types. The results were verified and confirmed using Principal Component Analysis (PCA) and RockWare (Aq.QA) software. We found that HCO3 was the most dominant anion throughout the country and that Cl and SO4 were only important in some local zones. The dominant cations were Na and Mg. Also, major ion ratios changed with geographical location and geological, and climatic conditions. •The analysis enabled the definition of seven groundwater types.•HCO3 is the dominant anion.•Mali groundwater is comparatively high in Na, Mg and HCO3.•Geographical location and environments have a greater influence on main ion proportions.•The regional chemical tendencies are reliable with geology and climate.