Management of Groundwater for Productive Uses in the Afram Plains Area, Ghana

Date of Award

2008

Document Type

Dissertation

Degree Name

Doctor of Environmental Management (D.Env.M)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Duke Ophori

Committee Member

Huan Feng

Committee Member

Danlin Yu

Committee Member

Solomon Gbondo-Tugbawa

Abstract

Groundwater is the main source of potable water for various uses in the Afram Plains area, Ghana. This study had the objective of assessing the quality and quantity of groundwater in the area for household and irrigation purposes. R-mode factor and hierarchical cluster analyses were combined with inverse geochemical modeling from PHREEQC and mineral stability diagrams, to determine the main contributors to the hydrochemistry of groundwater in the area. The sodium adsorption ratio, SAR, electrical conductivity, EC, sodium percent and permeability indices, PI, were then used to evaluate the suitability of groundwater in the area for irrigation purposes.

A 3-Dimensional groundwater flow model was developed from MODFLOW using available hydrogeological parameters of aquifers of the southern Voltaian sedimentary rocks in the Afram Plains area. The model was simulated for both steady state and transient state conditions. An optimization model highlighting the objectives to be achieved from the exploitation of groundwater resources in the area, the various environmental and economic constraints, was linked to the transient simulation model to provide a suitable management decision support system for groundwater resources in the area.

This study finds that groundwater hydrochemistry in the Afram Plains area is controlled by (i) silicate mineral weathering modulated by cation exchange processes (ii) carbonate mineral weathering and (iii) fertilizer from agricultural activities in the area. For the first time in the study area, the results of the hydrochemical modeling in this study suggests that silicate mineral weathering and cation exchange processes are the most pervasive processes in the area, and montmorillonite is the most stable mineral phase in the area. Stability in the montmorillonite field indicates that groundwater flow in the area is restricted. This finding is in consonance with the observed hydrogeology of the entire Voltaian System. In the assessment of the irrigation quality of the groundwater in the area, this study finds that more than 70% of the data used are within the range that is acceptable for irrigation of all crops in the area. This suggests that groundwater in the Afram Plains area is generally of acceptable quality will pose no or limited environmental problems when used for commercial irrigation activities in the area. This is the first comprehensive assessment of irrigation quality of groundwater in the Voltaian System of Ghana and will certainly prove handy in the management of groundwater resources in the terrain.

The flow simulation model, which is the first of its kind in the area, suggests that groundwater generally flows from the central areas to the outer regions, with water levels ranging from 50 m to 200 m. When combined with the optimization model, the transient model indicates that groundwater in the area has potential to meet current household and irrigation needs and holds significant promise for future uses. Commercial extraction for irrigation activities is however, much more feasible in the outer discharge areas than the central recharge areas.

Comments

Print version available at Sprague Library.

Full text available at ProQuest Dissertations & Theses Global.

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