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Groundwater occurrence in the Sakumo wetland catchment, Ghana: model–setting–scenario approach

Nonterah, Cynthia, Xu, Yongxin, Osae, Shiloh
Hydrogeology journal 2019 v.27 no.3 pp. 983-996
alluvium, aquifers, basins, dry season, evapotranspiration, groundwater, groundwater flow, humid tropics, rain, simulation models, subsurface flow, topsoil water, water storage, watersheds, wetlands, Ghana
Water flow is required for the health and integrity of any wetland environment. Based on field investigation, flow simulation and hydrogeological data, a conceptual flow model representing the physical characteristics of the Sakumo wetland (Ghana) was developed. Two major flow systems were identified: interflow (local topsoil water) in the alluvium and shallow groundwater flow in the unconfined unit. A simple two-dimensional finite-difference numerical model was applied to analyse the groundwater flow system in the Sakumo wetland catchment using ModelMuse. The purpose of the model was to explain the groundwater flow system and quantify the water fluxes contributing to the wetland water storage. The main source of groundwater for use in the catchment is the shallow unconfined Quaternary aquifer. The modelling results indicate that changes in recharge significantly affect the wetland water balance. The water table declines during the dry season as there is high evapotranspiration with little rain. The modelling results also confirm that the Sakumo wetland water fluxes are predominately associated with local shallow flows; the calibrated model simulation showed no hydraulic link between the wetland and the underlying deep basement aquifer. This study thus provides valuable hydrogeological information on the Sakumo wetland basin and lays the foundation for development of detailed future predictive models in this under-researched area of hydrogeology in the humid tropics.