Abstract
Groundwater resources in the floodplain wetlands of the White Volta River basin of Ghana is a major source of water for irrigation activities of communities living around and baseflow to sustain the flow of the river. Hydrology of the floodplain wetlands in the basin is complex, characterized by temporally variable storage volumes with erratic contribution to streamflow. For the continual usage of groundwater resources in the floodplains there is a need to study the form of interaction between the main river and floodplain wetlands. The study, adopted the PM-WIN (MODFLOW) model for simulating the interaction between the wetland and stream. Additionally, the lower boundary discharge output from the HYDRUS-1D model is the estimated recharge. This input quantifies the temporal and spatial variations in sub-surfaces discharges in the floodplain wetland. The simulation of the sub-surface hydraulic head of the wetland indicates a systematic variation relative to the White Volta River response to changes in the rainfall pattern. The interaction conditions vary from season to season with March, April, and May showing the least leakage (estimated values of 0.03 mm/day, 0.06 mm/day, and 0.15 mm/day, respectively) from the river into the floodplain wetland. Notably, the interaction between the wetland and the river as simulated is bidirectional. With most of the flow coming out from the river into the floodplain wetland, this condition persists in the months of August and September.
Highlights
Rivers are an extension or continuum of groundwater and surface waterflow, but they serve as a critical component of the riparian and riverine ecology (Woessner, 2000)
The riparian areas consisting of floodplain wetlands contribute to the direction of hydrological flows, but its connectivity to the main channel depend on the lithology, geology and landscape settings (Grape et al, 2006; Brooks, 2005)
The hydrology of the wetlands found in the basin is complex characterized by spatial and temporal variability of their volume and surface area
Summary
Rivers are an extension or continuum of groundwater and surface waterflow, but they serve as a critical component of the riparian and riverine ecology (Woessner, 2000). Floodplains wetlands in peak flows gets inundated and provides a lot of environmental benefits and services such as habitat for wildlife, water purification, groundwater recharge and production of biomass (Bridge 2005). These benefits emanate from the cumulative effects of heterogeneity of hydrological connections. As competing demand for wetland water resources within the White Volta River basin for agriculture and ecological activities are on the ascendency, studies (Ferdnald et al, 2001; Grapes et al, 2006) do not represent variability in wetland hydrological process and interaction with river system. This study is to fill gap in science by using numerical models to quantify and understand the connectivity and direction of flow between wetland and river flow in a sedimentary formation of a tropical system to inform management practices
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