Pra Basin Research Articles

Groundwater geochemical evolution, origin and quality in the Lower Pra Basin, Ghana: Insights from hydrogeochemistry, multivariate statistical analysis, mineral saturation indices, stable isotopes (δ2H and δ18O) and geostatistical analysis

Groundwater geochemical evolution, origin and quality in the Lower Pra Basin, Ghana: Insights from hydrogeochemistry, multivariate statistical analysis, mineral saturation indices, stable isotopes (δ2H and δ18O) and geostatistical analysis

Stable Isotopes and Water Level Monitoring Integrated to Characterize Groundwater Recharge in the Pra Basin, Ghana

In the Pra Basin of Ghana, groundwater is increasingly becoming the alternative water supply due to the continual pollution of surface water resources through illegal mining and indiscriminate waste discharges into rivers. However, our understanding of hydrogeology and the dynamics of groundwater quality remains inadequate, posing challenges for sustainable water resource management. This study aims to characterize groundwater recharge by determining its origin and mechanism of recharge prior to entering the saturated zone and to provide spatial estimates of groundwater recharge using stable isotopes and water level measurements relevant to groundwater management in the basin. Ninety (90) water samples (surface water and groundwater) were collected to determine stable isotope ratios of oxygen (δ18O) and hydrogen (δ2H) and chloride concentration. In addition, ten boreholes were installed with automatic divers to collect time series data on groundwater levels for the 2022 water year. The Chloride Mass Balance (CMB) and the Water Table Fluctuation (WTF) methods were employed to estimate the total amount and spatial distribution of groundwater recharge for the basin. Analysis of the stable isotope data shows that the surface water samples in the Pra Basin have oxygen (δ18O) and hydrogen (δ2H) isotope ratios ranging from −2.8 to 2.2‰ vrs V-SMOW for δ18O and from −9.4 to 12.8‰ vrs V-SMOW for δ2H, with a mean of −0.9‰ vrs V-SMOW and 0.5‰ vrs V-SMOW, respectively. Measures in groundwater ranges from −3.0 to −1.5‰ vrs V-SMOW for δ18O and from −10.4 to −2.4‰ vrs V-SMOW for δ2H, with a mean of −2.3 and −7.0‰ vrs V-SMOW, respectively. The water in the Pra Basin originates from meteoric source. Groundwater has a relatively depleted isotopic signature compared to surface water due to the short residence time of infiltration within the extinction depth of evaporation in the vadose zone. Estimated evaporative losses in the catchment range from 51 to 77%, with a mean of 62% for surface water and from 55 to 61% with a mean of 57% for groundwater, respectively. Analysis of the stable isotope data and water level measurements suggests a potential hydraulic connection between surface water and groundwater. This hypothesis is supported by the fact that the isotopes of groundwater have comparatively lower values than surface water. Furthermore, the observation that the groundwater level remains constant in months with lower rainfall further supports this conclusion. The estimated annual groundwater recharge in the catchment ranges from 9 to 667 mm (average 165 mm) and accounts for 0.6% to 33.5% (average 10.7%) of mean annual precipitation. The total estimated mean recharge for the study catchment is 228 M m3, higher than the estimated total surface water use for the entire Pra Basin of 144 M m3 for 2010, indicating vast groundwater potential. Overall, our study provides a novel insight into the recharge mechanism and spatial quantification of groundwater recharge, which can be used to constrain groundwater flow and hydrogeochemical evolution models, which are crucial for effective groundwater management within the framework of the Pra Basin’s Integrated Water Resources Management Plan.

The impact of artisanal gold mining on the sustainability of Ghana's river basins: The case of the Pra basin

The study examined the critical factors influencing the sustainability of the Pra river basin in Ghana, with a focus on water pollution incidents caused by illegal mining (galamsey) activities. The study followed a quantitative research approach using data collected from 156 respondents in the Amansie Central district of Ghana. Generally, Strengths-Weaknesses-Opportunities-Threats (SWOT), Analytical Hierarchy Process (AHP) as a multi-criteria technique in two stages of discrete and continuous sustainability analysis and descriptive statistics were the methods of analysis. The study revealed that licensing procedures that do not address environmental impacts, government ban on illegal mining (galamsey) activities as well as poor capacity and financial constraints greatly influence the sustainability of the Pra river basin. Also, self-cleansing capacity of the river basin as well as protection of the ecological status of water in the basin were respondents’ lowest priority. The results revealed that all criteria are currently within a sustainable range with a maximum score indicating a weak sustainability level of the basin due to the pollution incidents. Building on this empirical understanding calls for defensive strategies to be employed. The study therefore recommends amongst other things that revisiting the ban on illegal mining (galamsey) activities, and at this time, within the buffer zones of the basin area is critical for implementation. This, however, calls for a strong collaboration between government, civil society organizations and local communities towards addressing the environmental, economic and human aspects of water security, sustainability and management for the basin.

Studying Bankline Migration of the Lower Pra Basin using Remote Sensing and GIS

The study investigated bank erosion and accretion of the lower section of the Pra River of Ghana using a topographical map of 1974 and satellite imagery of 2007, 2015, and 2018 which was augmented by field observation and key informant interviews. Bankline changes due to erosion and accretion and the total volumetric change in river channel were measured using Remote Sensing and Geographic Information System approaches. The study showed that erosion was more pronounced in both the right and left bank as compared to accretion. The study revealed that bank width area of the lower basin of Pra River increased by 50.7 m² from 16.2 m² in 1974 to 66.9 m² in 2018 eroding large portions of land along the right and left banks of the river. In general, the number of erosional spots in selected cross sections exceeded that of deposition. Erosion took place in 13 spots out of 20 spots constituting 65% with a rate ranging between 0.2 and 3.4 m/year. This research showed the value of channel morphological analysis as it brought to the fore, a quantitative perspective to bank erosion and accretion processes of fluvial systems.

Water–Rock Interactions Driving Groundwater Composition in the Pra Basin (Ghana) Identified by Combinatorial Inverse Geochemical Modelling

The crystalline basement aquifer of the Pra Basin in Ghana is essential to the water supply systems of the region. This region is experiencing the ongoing pollution of major river networks from illegal mining activities. Water management is difficult due to the limited knowledge of hydrochemical controls on the groundwater. This study investigates its evolution based on analyses from a previous groundwater sampling campaign and mineralogical investigation of outcrops. The dominant reactions driving the average groundwater composition were identified by means of a combinatorial inverse modelling approach under the hypothesis of local thermodynamical equilibrium. The weathering of silicate minerals, including albite, anorthite, plagioclase, K-feldspar, and chalcedony, explains the observed median groundwater composition in the transition and discharge zones. Additional site-specific hypotheses were needed to match the observed composition of the main recharge area, including equilibration with carbon dioxide, kaolinite, and hematite in the soil and unsaturated zones, respectively, and the degradation of organic matter controlling the sulfate/sulfide content, thus pointing towards kinetic effects during water–rock interactions in this zone. Even though an averaged water composition was used, the inverse models can “bridge” the knowledge gap on the large basin scale to come up with quite distinct “best” mineral assemblages that explain observed field conditions. This study provides a conceptual framework of the hydrogeochemical evolution for managing groundwater resources in the Pra Basin and presents modelling techniques that can be applied to similar regions with comparable levels of heterogeneity in water chemistry and limited knowledge of aquifer mineralogy. The combinatorial inverse model approach offers enhanced flexibility by systematically generating all plausible combinations of mineral assemblages from a given pool of mineral phases, thereby allowing for a comprehensive exploration of the reactions driving the chemical evolution of the groundwater.

Hydrochemical Characterization of Surface Water and Groundwater in the Crystalline Basement Aquifer System in the Pra Basin (Ghana)

The quality of groundwater resources in the Pra Basin (Ghana) is threatened by ongoing river pollution from illegal mining. To date, there are very limited data and literature on the hydrochemical characteristics of the basin. For the first time, we provide regional hydrochemical data on surface water and groundwater to gain insight into the geochemical processes and quality for drinking and irrigation purposes. We collected 90 samples from surface water (rivers) and groundwater (boreholes) and analysed them for their chemical parameters. We performed a water quality assessment using conventional water quality rating indices for drinking water and irrigation. Cluster and factor analysis were performed on the hydrochemical data to learn the chemical variations in the hydrochemical data. Bivariate ion plots were used to interpret the plausible geochemical processes controlling the composition of dissolved ions in surface water and groundwater. The water quality assessment using Water Quality Index (WQI) revealed that 74% of surface water and 20% of groundwater samples are of poor drinking quality and, therefore, cannot be used for drinking purposes. For irrigation, surface water and groundwater are of good quality based on Sodium Adsorption Ratio (SAR), Wilcox diagram and United States Salinity (USSL) indices. However, Mn and Fe (total) concentrations observed in most surface water samples are above the acceptable limit for irrigation and therefore require treatment to avoid soil acidification and loss of availability of vital soil nutrients. Manganese and iron (total) are identified as the main contaminants affecting the basin’s water quality. The hierarchical cluster analysis highlights the heterogeneity in the regional hydrochemical data, which showed three distinct spatial associations based on elevation differences. Groundwater composition chemically evolves from a Ca–HCO3 to a Na–HCO3 and finally to a Na–Cl water type along the flow regime from the recharge to the discharge zone. The bivariate ion plot and the factor analysis underscore silicate weathering, carbonate dissolution and ion exchange as the most likely geochemical processes driving the hydrochemical evolution of the Pra Basin groundwater. Going forward, geochemical models should be implemented to elucidate the dominant reaction pathways driving the evolution of groundwater chemistry in the Pra Basin.

Water Quality Monitoring in the Pra Basin of Ghana

Water Quality Monitoring in the Pra Basin of Ghana

Effect of small-scale illegal mining on surface water and sediment quality in Ghana

ABSTRACT In Ghana, small-scale mining (SSM) has been carried out for many years, generating employment and income. Currently, illegal artisanal mining (‘galamsey’) has impacted the environment negatively, resulting in land degradation and water pollution. The government of Ghana, responding to public outcry against the negative effects of ‘galamsey’, placed a ban on illegal small-scale mining activities in March 2017. This ban stopped both ‘legal’ small-scale and the illegal artisanal miners from carrying out any such activity. In July 2018, this study was carried out to examine the status of water and sediment quality in eight endemic regions of illegal mining to ascertain the outcome of the ban on the water quality of the rivers. Methodologies in the Standard Methods for the Examination of Water and Wastewater were followed. Results of the study indicated that the rivers were high in total suspended solids (TSS), turbidity and colour, suggesting inflow of wastewater from the illegal mining activities and some run-off. Colour had a strong correlation with turbidity (r = 0.95) and TSS (r = 0.94), suggesting that the pollution originates from the same sources. Low levels of metals were found in both water and sediment. However, very high concentrations of Fe were detected in both water and sediment. Mercury concentrations were low in the water column but relatively higher in the sediment. A comparison of the general water quality status of the water bodies in the Pra Basin in 2013 and 2018 using the Water Quality Index (WQI) showed a marginal improvement in quality in 2018 over 2013 in the Pra Basin. The improvement of water quality in 2018 is attributable to the ban.

Advective Particle Transport Modelling of Potential Contaminated Source Sites in the Lower Pra Basin of Ghana

Advective Particle Transport Modelling of Potential Contaminated Source Sites in the Lower Pra Basin of Ghana

Evaluation of Sediment Yield Predicting Models of Ghana

Fluvial sediment transport data is a very important data for effective water resource management. However, acquiring this data is expensive and tedious hence sediment yield modeling has become an alternative approach in estimating river sediment yields. In Ghana, several sediment yield predicting models have been developed to estimate the sediment yields of ungauged rivers including the Pra River Basin. In this paper, 10 months sediment yield data of the Pra River Basin was used to evaluate the existing sediment yield predicting models of Ghana. A regression analysis between predicted sediment yield data derived from the models and the observed suspended sediment yields of the Pra Basin was done to determine the extent of estimation of observed sediment yields. The prediction of suspended sediment yield was done for 4 out of 5 existing sediment yield predicting models in Ghana. There were variations in sediment yield between observed and predicted suspended sediments. All predicted sediment yields were lower than observed data except for equation 3 where the results were mixed. All models were found to be good estimators of fluvial sediments with the best model being equation 4. Sediment yield tends to increase with drainage basin area.

An intervention to address deteriorating water quality: An application of Ajzen’s theory of planned behavior

This study investigates the factors which influence illegal miners’ intention to choose an alternative job using the theory of planned behavior (TPB). Three hundred and thirty-eight respondents from illegal mining communities in the Pra Basin completed a questionnaire on behavioral, social and demographic factors which might motivate an illegal miner to choose an alternative job. The attitude was found to be the only dominant significant antecedent of the behavioral intention. The findings from the study reveal that Perceived Behavioral Control (PBC) which has been the focus of the job intervention in the basin is not a predictor of their intention.

Assessment of Nutrients Levels in Groundwater within the Lower Pra Basin of Ghana

The level of concentration of nitrates, phosphates, and sulphates was determined in groundwater within the Pra Basin to ascertain the degree of anthropogenic influence via the application of fertilizer and other agro-chemical to farmlands by farmers. Sixty-five (65) boreholes in forty-five (45) communities were analysed between January and April 2012 to cover the dry season and between June and October 2012 to cover the wet season. The results show that nitrate for both seasons range between 0.011 mg/l and 5.01 mg/l and therefore within the WHO (2006) guideline value of 10 mg/l, whilst that of phosphate range between 0.01 mg/l and 3.08 mg/l and therefore outside the USEPA guideline value of 2.5 mg/l. Sulphate recorded a range between 1.60 and 96.2 mg/l and therefore within the WHO (2006) guideline value of 250 mg/l. The concentration levels of the two nutrients of the parameters, nitrates and phosphate were correlated against borehole depth and the results show a weak positive and negative correlation for nitrate and phosphate respectively. There was thus, an indication that the levels of all parameters, nitrate, phosphate and sulphate are not yet a threat to groundwater in the basin.

The effectiveness of water resources management in Pra Basin

Abstract Integrated water resources management (IWRM) has been criticized yet it is the dominant approach to water resources management in developing countries. The criticism emanates from the manifold unfounded assumptions made during implementation on issues such as availability of technology and infrastructure, privatization and sustainable financing, human resource capacity, government interference, etc. The Pra Basin has been implementing IWRM since 2011. The basin houses nine out of the 17 artificial reservoirs constructed in Ghana for drinking water supply. It is therefore prudent that the basin's water resources are given extra management care to ensure sustainable water quality and quantity for growth and development. However, much uncertainty still exists about whether the best water management system is being practiced, whether the system is working well, or needs improvement. This study examines the effectiveness of water resources management in the Pra Basin of Ghana. This study used interviews, field observations, and documents such as Pra Basin IWRM plan, the national IWRM plan, etc., to assess the effectiveness of IWRM in the Pra Basin. The result of the study showed that IWRM although appropriate for the basin had implementation gaps. These gaps are potential contributors to deteriorating water quality.

Evaluation of Satellite Rainfall Estimates in the Pra Basin of Ghana

Availability of gauged rainfall data in most developing countries at good resolution is usually a challenge since meteorological stations are usually located near urban areas. In cases where data is available some stations may still have a lot of missing values. However, in recent times, satellite derived rainfall estimates provide an alternate source of rainfall data in areas where conventional rainfall measurements are not readily available. This study evaluated the accuracy of three satellite rainfall products, TMPA 3B42RT, TMPA 3B42 and CMORPH, in the Pra basin of Ghana. Using the point-to-pixel method, data extracted from 0.25°× 0.25° satellite grids were compared with gauged rainfall measurements and analyzed using correlation coefficient (r), bias and percent bias (%Bias) as the performance evaluation methods. Seven (7) gauge stations with no missing data for the period 2003–2008 were used in the evaluation. The results, following the analysis of the data at daily, monthly, annual and seasonal timescales, showed that TMPA products performed better on all timescales considered. CMORPH on the other hand showed overestimation at all gauge locations. The TMPA 3B42 was seen to be the best amongst the three products. The overall rainfall in the basin was well depicted by the TMPA 3B42 and 3B42RT. Although there was not a perfect match between the 3B42RT and 3B42 products and the gauged rainfall, these products can be used to supplement gauged rainfall measurements in the basin and in estimation of rainfall in ungauged basins with similar characteristics.

Assessment of Heavy Metal Pollution in the Sediments of the River Pra and Its Tributaries

An investigative study was conducted to determine the heavy metal pollution in the sediment in the Pra Basin of Ghana from 27 sampling points during the dry and wet seasons using the geo-accumulation index (Igeo), enrichment factor (EF), and pollution load index (PLI). Sediments were acid digested and analyzed for the following selected metals: arsenic (As), lead (Pb), cadmium (Cd), zinc (Zn), manganese (Mn), total chromium (Cr), nickel (Ni), and iron (Fe) using the dual atomizer and hydride generator atomic absorption spectrophotometer (model ASC-7000 No A309654, Shimadzu, Japan). The metal concentrations (mg kg−1) in the sediments were as follows: As (0.175) < Cd (3.206) < Ni (79.927) < Zn (118.323) < Cr (216.708) < Mn (234.742) < Pb (335.381) < Fe (1354.513) in the dry season and As (0.002) < Cd (7.279) < Ni (72.663) < Zn (35.622) < Pb (135.863) < Cr (167.604) < Mn (183.904) < Fe (1138.551) for the wet season. The EF which is an indication of whether metal concentrations are due to anthropogenic activities shows enrichment at all site for the metals Cr, Pb, and Cd in the wet seasons. However, only 4 out of the 27 sites showed Ni enrichment in the wet season. Contrary to the wet season, only Pb and Cr recorded enrichment at all sites during the dry season. Fifteen out of the 27 sites recorded Cd enrichment and 24 out of the 27 sites recorded Ni enriched during the dry season. None of the sites were enriched with Fe, As, Zn, and Mn in either the dry or wet seasons. For both dry and wet seasons, the pollution load index for all the sites except one was at the background levels which is a sign of non-deterioration of the sites studied. In the wet season, the calculated Igeo reveals that the study area is not contaminated with respect to As, Zn, Fe, and Mn; uncontaminated to moderately contaminated with Cd; moderately contaminated with Cr; uncontaminated to moderately to heavily contaminated with Ni; and moderately to heavily contaminated with Pb. The dry season Igeo results reveal non-contamination of the study area with respect to As, Fe, and Mn; uncontaminated to moderately contaminated with Zn; moderately contaminated with Cr; uncontaminated to heavily contaminated with Cd; uncontaminated to extremely contaminated with Ni; and moderately to extremely contaminated with Pb. The high levels of Cd, Pb, and Cr in all the sites are due to unregulated illegal mining activities occurring in and around the study area. It is hoped that this study will prompt the basin management board to improve their management strategies in controlling unregulated illegal mining in the basin sediments.

Effects of small-scale gold mining on heavy metal levels in groundwater in the Lower Pra Basin of Ghana

The effects of small-scale gold mining activities on heavy metal levels in groundwater were determined for the Lower Pra Basin of Ghana. Sixty five boreholes in 45 communities were analysed between January 2012 and April 2012 for the dry season and June and October 2012 for the wet season. The test for significance and the use of cluster analysis, a multivariate approach, clearly delineate Cu, Zn, Cd and Hg as possible anthropogenic contributors, whilst As, Se and Pb could be both anthropogenic and natural geochemical process contributors of metal level concentrations in the groundwater. The analysis shows generally low pH values in the basin with more than 95% of dry season and almost all wet season values being acidic or slightly acidic. Approximately 35% of boreholes in the wet season recorded values for cadmium above WHO guideline value of 3.0 µg/l with almost all dry season values falling below 3.0 µg/l except for two boreholes. Generally, high values were recorded for iron, manganese, lead, Al and Hg. In general, lead, copper, cadmium and manganese showed higher wet season values than dry season suggesting anthropogenic influence.

Assessment of heavy metal pollution in the main Pra River and its tributaries in the Pra Basin of Ghana

The Pra Basin is one of the Basins in Ghana with a high level of illegal mining activities. Heavy metal pollution in water bodies is common in areas where illegal mining is practiced. This study focused on the assessment of heavy metal pollution in the Pra Basin. The study was based on 216 water samples collected from 27 sampling points from the Pra River and two of its tributaries during the dry and wet seasons in 2017. Nine heavy metals namely arsenic (As), chromium (Cr), cadmium (Cd), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn), and iron (Fe) were assessed in this study. The metal concentrations (mg L−1) in the water were as follows: Fe > Pb > Ni > Cu > Cr > Cd > Zn > Mn > As and in the dry season as Fe > Zn > Cu > Cr > Pb > Mn > Ni > Cd > As. Five metals exceed the safe drinking water guidelines making the water generally not safe for domestic activities like drinking and cooking. According to the Nemerow’s Pollution Index (NPI) results, six metals namely Pb, Cd, Cr, Ni, Fe, Zn were the principal metal pollutants in both the dry and wet seasons whereas Mn, As, and Cu, were found not to contribute to the pollution effect. The water quality index confirms that the water quality is marginal to fair in the dry season and poor for 26 out of the 27 sites in the wet season. Generally the studied rivers (Pra, Offin and Oda) are polluted which is a serious threat to the health of inhabitants in villages which still use the water for cooking activities. The study recommends continuous monitoring of the polluting metals and the assessment of the river sediments to inform effective remediation measures.

Application of multivariate statistical technique for hydrogeochemical assessment of groundwater within the Lower Pra Basin, Ghana

Multivariate statistical technique and hydrogeochemical approach were employed for groundwater assessment within the Lower Pra Basin. The main objective was to delineate the main processes that are responsible for the water chemistry and pollution of groundwater within the basin. Fifty-four (54) (No) boreholes were sampled in January 2012 for quality assessment. PCA using Varimax with Kaiser Normalization method of extraction for both rotated space and component matrix have been applied to the data. Results show that Spearman’s correlation matrix of major ions revealed expected process-based relationships derived mainly from the geochemical processes, such as ion-exchange and silicate/aluminosilicate weathering within the aquifer. Three main principal components influence the water chemistry and pollution of groundwater within the basin. The three principal components have accounted for approximately 79% of the total variance in the hydrochemical data. Component 1 delineates the main natural processes (water–soil–rock interactions) through which groundwater within the basin acquires its chemical characteristics, Component 2 delineates the incongruent dissolution of silicate/aluminosilicates, while Component 3 delineates the prevalence of pollution principally from agricultural input as well as trace metal mobilization in groundwater within the basin. The loadings and score plots of the first two PCs show grouping pattern which indicates the strength of the mutual relation among the hydrochemical variables. In terms of proper management and development of groundwater within the basin, communities, where intense agriculture is taking place, should be monitored and protected from agricultural activities. especially where inorganic fertilizers are used by creating buffer zones. Monitoring of the water quality especially the water pH is recommended to ensure the acid neutralizing potential of groundwater within the basin thereby, curtailing further trace metal mobilization processes in groundwater within the basin.

Estimating Recent Sedimentation Rates Using Lead-210 in Tropical Estuarine Systems: Case Study of Volta and Pra Estuaries in Ghana, West Africa

The Volta River and its basin form about one-third of Ghana's total land area and contributes significantly to the hydrological network of the country’s river system while River Pra basin is noted for large and small scale mining activities within it. Both river systems are important for sediment delivery for beach nourishment along Ghana’s coast. This work presents the first ever estimates of the sedimentation rates at the estuaries of these rivers using 40 cm long sediment cores. Sediment accumulation rates were estimated using the 210Pb sediment dating technique which is based on alpha and gamma emitting radionuclides. The total 210Pb concentration in the sediment was measured with an alpha spectrometer while the activities of supported 210Pb and 137Cs were measured with a gamma spectrometer with high germanium n-type detector. The unsupported 210Pb was determined by subtraction of the supported from the total at each core sediment level. Irregularities in the 210Pb activity versus depth profile, indicated variation in the net sedimentation accumulation rate during the past 96 and 182 years at the Volta and Pra estuaries, respectively. From the CRS model calculations, sedimentation rates varied markedly before (1.1 gcm-2y-1) and after (0.5 gcm-2y-1) construction of the Akosombo dam resulting in about 50% drop in sedimentation rate at the Volta estuary. Sediment accumulation rates were relatively low at the Pra estuary compared to the Volta estuary. Depositional fluxes of 210Pb were 190.1 ± 15.9 Bqcm-1y-1 and 217.8 ± 11.8 Bqcm-1y-1 in Pra and Volta estuaries respectively. 137Cs profile did not show defined peaks. However, the ages and sedimentation rates were better explained using historical events and anthropogenic activities that occurred within the catchment areas, providing a better understanding of deficit in sediment budget caused by hydric erosion processes prevailing in the Ada and Keta beaches in Ghana, due to reduction of sediment input from the Volta estuary.

Levels, source determination and health implications of trace metals in groundwater within the Lower Pra Basin, Ghana

Two hundred and fifty samples were collected from fifty-five (No) boreholes on quarterly basis between March 2011 and October 2012 covering the wet and dry seasons within the Lower Pra Basin for water quality assessment. The analytical results show that groundwater being used by some communities within the basin is contaminated, with Al (19.2 % of boreholes), Se (18.4 % of boreholes), Cd (18 % of boreholes), As (11.6 % of boreholes), Pb (39.6 % of boreholes), Mn (5.6 % of boreholes), Hg (42 % of boreholes) and Fe (21.6 % of boreholes) at levels exceeding the WHO (Guidelines for drinking water quality. Revision of the 1993 guidelines, 2004) guideline limits for drinking water. The stability of iron species for the groundwater system under the prevailing pE/pH condition shows that amorphous Fe(OH)3 significantly controls the concentration of iron in groundwater within the basin. The results also show that pyrite and arsenopyrite oxidation processes in groundwater within the basin are not exclusively responsible for the concentration of iron in the boreholes. Calculated saturation indices (SI) of the iron and manganese species using PHREEQC for Windows show that the groundwaters are generally undersaturated with respect to melanterite (FeSO4·7H2O), siderite (FeCO3), hausmannite (Mn3O4), pyrolusite (MnO2), rhodochrosite (MnCO3), manganite (MnOOH) and pyrochroite [Mn(OH2)], and supersaturated with respect to goethite (FeOOH) and haematite (Fe2O3). Human health risks assessment show that, for both adults and children via ingestion route, the mean HQing levels were found in the order of Zn > Fe = Cu > Pb > Cd >Mn. Results further show that the HQ/HI is the same for both adults and children for all trace metals and are less than 1. Thus, the trace metals considered in this study are not of concern for potential human health risk caused by exposure to non-carcinogenic elements.