Analysis of groundwater quality using water quality index and conventional graphical methods: the Volta region,Ghana |
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| Authors: | Bruce Banoeng-Yakubo Sandow Mark Yidana Nti Emmanuel Thomas Akabzaa Daniel Asiedu |
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| Institution: | (1) Department of Geology, University of Ghana, Legon, Accra, Ghana;(2) Department of Natural Resources, Utah Geological Survey, 1594 W North Temple suite 3110, Salt Lake City, UT 84116, USA; |
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| Abstract: | Conventional graphical and statistical methods were used with water quality indices to characterize the hydrochemistry of
groundwater from the northern part of the Volta region of Ghana. The objective was to determine the processes that affect
the hydrochemistry and the variation of these processes in space among the three main geological terrains: the Buem formation,
Voltaian System and the Togo series that underlie the area, and to determine the suitability of groundwater from the area
for drinking purposes. The Q-mode cluster analysis reveals three main water groups. The groups established from the Q-mode
HCA appear to indicate different degrees of weathering which could further indicate varying levels of fracturing aquifer hydraulic
properties. R-mode HCA and factor analysis (using varimax rotation and Kaiser Criterion) were then applied to determine the
significant sources of variation in the hydrochemistry. This study finds that groundwater hydrochemistry in the area is controlled
by the weathering of silicate and carbonate minerals, as well as the chemistry of infiltrating precipitation. Mineral activity
diagrams for the CaO–Na2O–Al2O3–SiO2–H2O and CaO–MgO–Al2O3–SiO2–H2O systems plotted for the area indicate stability in the smectite field and attribute hydrochemistry to the weathering of
silicate minerals. Silicate mineral weathering and the effects of precipitation appear to be pervasive among all the three
main geological terrains, whereas carbonate weathering is localized among the Voltaian aquifers. Cation exchange does not
appear to play a significant role in the hydrochemistry but mild Water quality indices (WQI) were calculated for the samples
using the concentrations of Na+, Ca2+, Mg2+, Cl−, NO3
−, F−, and EC at the various sample locations. The WQI values indicate that groundwater from the study area is of excellent quality
for drinking purposes. WQI values from groundwater samples are averagely higher than samples taken from surface water sources
in the area. This implies that geology has had an impact on the WQI of groundwater in the area. |
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