This study demonstrates the application of multivariate statistical methods in definition of groundwater recharge and discharge areas in a sedimentary basin in Ghana. Q-mode hierarchical cluster analysis (HCA) was applied to 57 hydrochemical data from the Buem formation in the northern part of the Volta Region in Ghana. R-mode HCA and R-mode factor analysis were then applied to the same dataset to reveal the processes controlling the hydrochemistry of groundwater from this hydrogeological formation. Results of both the Q- and R-mode analyses were backed by graphical methods. The analyses revealed two major water types, differentiated by salinity levels into four spatial groundwater associations. The characteristics of the four groundwater types are discussed. The recharge areas are characterized by CaHCO3 low salinity waters which evolve through rock–water interactions to NaHCO3 high salinity waters in the discharge areas. This study finds that the hydrochemistry of groundwater from this formation is mainly controlled by the weathering of minerals, principally silicates in the aquifer matrix. The effects of the chemistry of recharging precipitation are higher in the recharge areas, while mineral weathering tends to be severe close to the discharge areas in the groundwater flow regime. All the four spatial groundwater associations have low sodium content, but salinity levels increase towards the discharge areas, such that some of wells in the discharge areas may not be acceptable for irrigation on grounds of high salinities which might affect the osmotic potentials of plants. Copyright © 2011 John Wiley & Sons, Ltd.