Groundwater classification using multivariate statistical methods: Birimian Basin, Ghana

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Abstract

Groundwater from the aquifers of Birimian system in the northern and southern sections of the country was sampled for the concentrations of the major ions in the area. The objective was to determine the spatial groundwater associations which will in turn be used to infer the position of each groundwater group in the flow system. In addition, this study intended to determine the major sources of variation in the hydrochemistry and the suitability of groundwater from aquifers of the Birimian system for irrigation activities. R-mode factor and Q-mode hierarchical cluster analyses were used together with conventional graphical techniques. This study revealed four groundwater associations (clusters) representing three major groundwater types in the Birimian System: the Ca- HCO3 water types which make up Clusters (groups) 1 and 2 members; the Na-K-Cl water types comprising cluster 3 members, and Mg- HCO3 water types comprising Cluster 4 members. Cluster 2 has the lowest average electrical conductivity of 194 mS/m with total dissolved solids (TDS) ranging between 50 and 250 mg/L. This is the freshest groundwater type in the area and is typical of groundwater in recharge areas of the groundwater flow system. Cluster 1 members range in salinity between 50 and 500 mg/L. The highest average salinity is contained in Cluster 3, with TDS in the range of 300 to 1,000 mg/L, which is characteristic of groundwaters in discharge areas of the groundwater flow system. Members of this group are also characterized by high fluoride concentrations; average fluoride concentration in this group is 4.60 mg/L. Cluster 3 is the least desirable of the four clusters, for domestic water supply. Cluster 4 has TDS in the range of 300 and 1,000 mg/L, with low fluoride content. This study finds that the hydrochemistry of groundwater in the terrain is controlled by three major factors: silicate mineral weathering and cation exchange, carbonate mineral weathering, and chemical fertilizers from farms in the area. All the groundwater clusters have low sodium content and will not pose the sodium hazard when used for irrigation. However, as a result of high permeability indices, all but one of the Cluster 2 members plot within the class III region of the Doneen's chart and are therefore unsuitable for irrigation on these grounds. Clusters 3 and 4 members are the best water types, while Cluster 1 members are equally distributed between Classes II and III categories.

Original languageEnglish
Pages (from-to)1379-1388
Number of pages10
JournalJournal of Environmental Engineering
Volume136
Issue number12
DOIs
Publication statusPublished - Dec 2010

Keywords

  • Adsorption
  • Africa
  • Birimian system
  • Classifications
  • Electrical conductivity
  • Factor analysis
  • Ghana
  • Groundwater management
  • Hierarchical cluster analysis
  • Permeability index
  • Sodium
  • Sodium adsorption ratio

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