Aquifer vulnerability is a critical issue across the entire globe due to the depletion of groundwater and escalation of pollution levels, which poses a detrimental effect on the natural environment. To ascertain this ...Aquifer vulnerability is a critical issue across the entire globe due to the depletion of groundwater and escalation of pollution levels, which poses a detrimental effect on the natural environment. To ascertain this contamination risk, an extensive study has been conducted to assess the aquifer vulnerability by using the F-hydra model. This paper presents the vulnerability technique for the theory and application of flow accumulation, land-use and hydraulic conductivity. The model was applied to a shallow aquifer in eastern Ghana’s Volta River Basin, with the results being compared to the standardised DRASTIC model. The model follows the aquifer vulnerability assessment concept of the source pathway receptor where flow accumulation represents the ponding areas with downward percolation of contaminant to the water table, land-use represents the human activities at the land surface, and hydraulic conductivity represents the driving force leading to the movement of contaminant. The results reveal that the moderate vulnerability region covers 51.55% (2598.12 km<sup>2</sup>) of the entire area. The high and low vulnerability regions cover a significant percentage of the area 1.13% (56.52 km<sup>2</sup>) and 47.32% (2384.93 km<sup>2</sup>), respectively. The final vulnerability index was largely influenced by the removal of the hydraulic conductivity and land-use parameters. The model was validated with nitrate concentration in drilled wells in the study area. The maps produced in this study could be utilised as a guide to vulnerability by policymakers, groundwater manager and planners aimed at preserving the integrity of this vulnerable resource.展开更多
The purpose of this study was to evaluate the effects of Broussonetia papyrifera(paper mulberry)invasion and land use on the floristic composition of a dry semideciduous forest in Ghana.Forty-five plots(25 m×25 m...The purpose of this study was to evaluate the effects of Broussonetia papyrifera(paper mulberry)invasion and land use on the floristic composition of a dry semideciduous forest in Ghana.Forty-five plots(25 m×25 m each),distributed among three land uses-selectively logged(SL);abandoned farmlands(AF);and an undisturbed reference(RF)-were surveyed.Results showed lower tree species richness(S),diversity(H’),evenness(S)and basal area(BA)in the SL(46,0.78,0.32 and 269.12 m2 ha-1,respectively)and AF(40,0.53,0.45,and 131.16 m^2 ha^-1)sites compared to the RF site(79,2.66,0.87,963.72 m^2 ha^-1).Similar patterns were found at the shrub layer,but no differences were observed at the herb layer.Non-metric multidimensional scaling ordination revealed distinct species composition among the land uses.The two disturbed habitats,SL and AF,were associated with increased B.papyrifera invasion particularly in the overstory,with importance value index and mean relative density of 45 and 65.03%,and 42 and 53.29%,correspondingly.However,the species was only sparsely represented in the RF site.Tree density of B.papyrifera correlated negatively with H’,S,E,BA,and native tree density and richness.These findings highlight the strong link between human land use(i.e.,logging and slash-andburn farming),invasion,and vegetation characteristics,and suggest the need to limit these disturbances to conserve biodiversity within tropical forest ecosystems.展开更多
文摘Aquifer vulnerability is a critical issue across the entire globe due to the depletion of groundwater and escalation of pollution levels, which poses a detrimental effect on the natural environment. To ascertain this contamination risk, an extensive study has been conducted to assess the aquifer vulnerability by using the F-hydra model. This paper presents the vulnerability technique for the theory and application of flow accumulation, land-use and hydraulic conductivity. The model was applied to a shallow aquifer in eastern Ghana’s Volta River Basin, with the results being compared to the standardised DRASTIC model. The model follows the aquifer vulnerability assessment concept of the source pathway receptor where flow accumulation represents the ponding areas with downward percolation of contaminant to the water table, land-use represents the human activities at the land surface, and hydraulic conductivity represents the driving force leading to the movement of contaminant. The results reveal that the moderate vulnerability region covers 51.55% (2598.12 km<sup>2</sup>) of the entire area. The high and low vulnerability regions cover a significant percentage of the area 1.13% (56.52 km<sup>2</sup>) and 47.32% (2384.93 km<sup>2</sup>), respectively. The final vulnerability index was largely influenced by the removal of the hydraulic conductivity and land-use parameters. The model was validated with nitrate concentration in drilled wells in the study area. The maps produced in this study could be utilised as a guide to vulnerability by policymakers, groundwater manager and planners aimed at preserving the integrity of this vulnerable resource.
基金supported by the Institute for Environmental and Sanitation Studies,University Ghana,Legon,Accra,Ghana
文摘The purpose of this study was to evaluate the effects of Broussonetia papyrifera(paper mulberry)invasion and land use on the floristic composition of a dry semideciduous forest in Ghana.Forty-five plots(25 m×25 m each),distributed among three land uses-selectively logged(SL);abandoned farmlands(AF);and an undisturbed reference(RF)-were surveyed.Results showed lower tree species richness(S),diversity(H’),evenness(S)and basal area(BA)in the SL(46,0.78,0.32 and 269.12 m2 ha-1,respectively)and AF(40,0.53,0.45,and 131.16 m^2 ha^-1)sites compared to the RF site(79,2.66,0.87,963.72 m^2 ha^-1).Similar patterns were found at the shrub layer,but no differences were observed at the herb layer.Non-metric multidimensional scaling ordination revealed distinct species composition among the land uses.The two disturbed habitats,SL and AF,were associated with increased B.papyrifera invasion particularly in the overstory,with importance value index and mean relative density of 45 and 65.03%,and 42 and 53.29%,correspondingly.However,the species was only sparsely represented in the RF site.Tree density of B.papyrifera correlated negatively with H’,S,E,BA,and native tree density and richness.These findings highlight the strong link between human land use(i.e.,logging and slash-andburn farming),invasion,and vegetation characteristics,and suggest the need to limit these disturbances to conserve biodiversity within tropical forest ecosystems.
