The Densu River Basin is one of the important basins in Ghana. A large number of residents in this basin are dependent on groundwater for their livelihood. However, with the growing population, urbanization and impact of climate change, it is imperative to develop ways to protect and manage the limited groundwater resource that is supporting the communities. As a result, this paper assessed the groundwater vulnerability by comparing two methodsthe Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of the vadose zone, and hydraulic Conductivity DRASTIC an the Aquifer Vulnerability Index (AVI). The results show that DRASTIC is more precise and representative of the groundwater vulnerability in the basin. The AVI statistically show a relatively lower risks compared to DRASTIC. It is recommended, AVI which is oversimplified may be useful for larger basins.

Groundwater resources continue to be an important source of water supply for communities in developing countries. However, rapid population growth and urbanization, challenges the potential of groundwater to serve and meet the needs of growing populace. Various techniques have been developed over the last decade to assess groundwater vulnerability due

Arsenic (As) analysis of 150 boreholes in the southeastern part of Ghana (Accra, Eastern and Volta regions) revealed low to medium concentrations in the range of 2-39 µg l-1 , with only 2% of boreholes tested having arsenic concentration exceeding 10 µg l-1 of the WHO (2004) maximum permissible level of arsenic in drinking water. The measurements were carried out in the field using the Wagtech Arsenator field test kit (Wag-We 100500) equipment, which gives direct readout of arsenic concentration in the critical range 2-100 µg l-1. Arsenic concentrations were in the range < 2-39 µg l-1 with mean (< 2 µg l-1) and median (< 2 µg l-1). Out of 150 samples analysed, 147 had As concentration below 10 µg l-1. Three boreholes in the Recent Sand Formation in southern Volta Region at Atitekpo, Mafi Devime and Woe Aklorbordzi had arsenic concentrations of 28 µg l-1 , 19 µg l-1 and 39 µg l-1 , respectively. Though the sample of boreholes tested was only approximately 10% of the total number of boreholes in the study, the distribution within the sample makes the generalization that the risk of arsenic contamination of rural water supply in southeastern Ghana is generally low plausible. In spite of this assertion, boreholes in the Recent Sandy Formation have to be critically assessed to determine the extent of arsenic contamination and, if possible, monitored.

Evapotranspiration is an important component necessary for ensuring efficient management of water resources for every river basin. The Bui Hydroelectric Plant completed early 2014 to provide electricity for the people of Ghana is located within the Black Volta River Basin of West Africa. With the construction of this plant and related developments, there is a need for attention to be paid to the conservation of water resources within this basin. This paper therefore assesses the spatial temporal behaviour of evapotranspiration within the basin from 2001 to 2013 and compares this with the average monthly rainfall estimates from 1983 to 2012. The assessment shows that the average monthly evapotranspiration is within 0 to 150 mm/month for the period assessed. However, significant variation exists between the years with a highly erratic pattern observed. The pattern of the rainfall indicates that the upstream portion of the basin receives lower rainfall compared to the downstream portion of the basin. This pattern is consistent with the overall variation of the evapotranspiration within the basin. This spatial-temporal behaviour is an important factor that needs to be considered by all stakeholders given the anticipated land-use changes expected within the basin coupled with likely future increases in temperatures resulting from climate change.