Millicent Obeng Addai

MILLICENT OBENG ADDAI PhD THESIS

SUPERVISORS

Prof. Sandow Mark Yidana – Principal Supervisor

Prof. Peter Engesgaard

Prof. Clement Alo

Dr. Larry Pax Chegbeleh

Millicent’s PhD thesis has been focused on developing a 3D transient hydrogeological model over the Nasia Basin. In order to achieve this, there has been the need to obtain data from various sources and conduct field work. Millicent obtained relevant historical data on the geology, hydrogeology, and hydroclimatology from various institutions: Water Resources Commission through the database of the Hydrogeological Assessment Project; the Community Water and Sanitation Agency; World Vision International; Hydrological Services Department; Ghana Meteorological Services; Private Hydrogeological Consultants. The datasets obtained were used to develop a preliminary conceptual hydrogeological model over the terrain. She then participated in various field activities involving geophysical surveys, geological mapping, groundwater sampling of existing boreholes/wells, drilling of 10 boreholes for groundwater level monitoring and for additional information to constrain the preliminary conceptual model of the terrain.

The geophysical surveys provided data for constraining the top weathered zone and the stratigraphy of the terrain. Drilling 10 additional boreholes distributed over the terrain provided an opportunity to further confirm the litho/hydrostratigraphy. Eight of the 10 boreholes were fitted with data loggers to monitor the variations in groundwater levels in the terrain. Five additional boreholes were adopted from the HAP projected and fitted with data loggers for transient groundwater level monitoring. On the basis of the various datasets, Millicent developed and validated a conceptual model which formed the basis for developing a transient groundwater model over the terrain. The calibrated groundwater flow model was used to assess the impacts of natural and anthropogenic stresses, including climate change, on the sustainability of groundwater resources in the terrain.

Millicent is currently developing two manuscripts from the thesis. However, on September 22, 2020, she successfully defended her thesis by passing the Viva session. She is expected to submit the final corrected version of her thesis to the School of Graduate School soon.

Key Findings from Millicent’s Research

• Clear definition of the hydrostratigraphy to comprise the Alluvium+Saprolite, the Saprock, Fractured Bedrock and the fresh bedrock;

A detailed stratigraphy revealing the main lithologies from the top to bottom of one of the boreholes drilled in the study area.

The conceptualized hydrostratigaphy of the study area showing the main hydrostratigraphic units in the study area.

Thicknesses of the various hydrostratigraphic units as determined from borehole logs and geophysical data over the terrain.

• The terrain is unconfined to semi-confined, allowing direct groundwater recharge from rainfall and interaction between the stream network and groundwater in the terrain;
• A 3D transient hydrogeological model has been developed over the terrain. This model will continuously be updated with new monitored groundwater level data for use in decision-making on resource development;
• Estimated groundwater recharge in the study area falls in the range of 1.1% to 6.2% with an average of 3% of the annual rainfall in the area.