Geophrey Anornu

Tracking nitrate sources in groundwater and associated health risk for rural communities in the White Volta River basin of Ghana using isotopic approach (δ15N, δ18ONO3 and 3H)

In this study, we present a first attempt on the use of integrated hydro-chemical and isotopic technique to trace the sources of groundwater nitrate contamination in the Upper East Region of Ghana to aid the sustainable management of this vital resource. The objectives of the study are (1) assess the present status and spatial distribution of the nitrate contamination (2) identify and distinguish the most likely sources of nitrate , (3) identify the relationship between 3H and NO3- and F-, and (4) ascertain the potential human risk from exposure to nitrate contamination. The results showed that, nitrate concentrations varied from 0.42 to 431.17, 0.83 to 143.94, 0.03 to 28.94mg/l with mean values of 36.09, 21.54 and 5.01mg/l for boreholes, hand dug wells and the surface water respectively. These values showed that, about 95% of boreholes and hand dug wells and 45% of the surface water have nitrate concentration above the baseline value in the area. The NO3-/Cl- ratio showed that, 98.4%, 95% and 64% of the NO3- in the borehole, hand dug wells and the surface water are from anthropogenic activities. The δ15NNO3 and δ18ONO3- data confirmed that NO3- in the samples was predominantly derived from manure (human and animal waste) and denitrification occurring in some areas. The isotopic data further affirms the hydro-chemical interpretation that, chemical fertilizer and atmospheric deposition are unlikely sources of NO3- in the area. The relationship between 3H and NO3- concentrations showed that, higher NO3- values are associated with younger waters. Non carcinogenic health risk for adults and children posed by oral ingestion of the NO3- contaminated water revealed some degree of health risk, especially to children whose risk is about 72% higher. The study provides a conceptual model of the NO3- dynamics and some recommendation for groundwater management in the area.

Evaluation of Groundwater Vulnerability in the Densu River Basin of Ghana

The paper evaluated the potential of groundwater pollution in the Densu River Basin of Ghana. Groundwater is an important resource in this basin currently supporting domestic, agricultural and industrial activities. The significance of water resources and the potential for groundwater quality to deteriorate due various anthropogenic activities within the Densu River Basin has necessitated this study using a combination of GIS and DRATIC methods. The study reveal that about 47% of the basin is exposed to high-risk, 43% exposed to medium-risk and 10% exposed to low-risk. It is recommended that the fast growing urban settlements in this high-risk prone areas need more careful urban planning of settlements, siting of irrigation schemes and sanitation facilities. The results in this research are replicable in other basins in Ghana and the sub-region.

Analysis of climate and anthropogenic impacts on runoff in the Lower Pra River Basin of Ghana

The Lower Pra River Basin (LPRB), located in the forest zone of southern Ghana has experienced changes due to variability in precipitation and diverse anthropogenic activities. Therefore, to maintain the functions of the ecosystem for water resources management, planning and sustainable development, it is important to differentiate the impacts of precipitation variability and anthropogenic activities on stream flow changes. We investigated the variability in runoff and quantified the contributions of precipitation and anthropogenic activities on runoff at the LPRB. Analysis of the precipitation–runoff for the period 1970–2010 revealed breakpoints in 1986, 2000, 2004 and 2010 in the LPRB. The periods influenced by anthropogenic activities were categorized into three periods 1987–2000, 2001–2004 and 2005–2010, revealing a decrease in runoff during 1987–2000 and an increase in runoff during 2001–2004 and 2005–2010. Assessment of monthly, seasonal and annual runoff depicted a significant increasing trend in the runoff time series during the dry season. Generally, runoff increased at a rate of 9.98 × 107m3yr−1, with precipitation variability and human activities contributing 17.4% and 82.3% respectively. The dominant small scale alluvial gold mining activity significantly contributes to the net runoff variability in LPRB.