| Popis: |
Invasive alien tree species are known to use significantly more water than local indigenous trees; however, quantifying the effect of these trees on groundwater resources is a challenging task. We are currently investigating aquifers and recharge at the Dayspring Children’s Village. There is a large stand of mature invasive alien trees which is proposed to be depleting a shallow groundwater aquifer. We have collected gravity, magnetic, resistivity, refraction seismic and TEM data to map out the subsurface and determine temporal variations in the groundwater. Structural controls, such as fractures, appear to host the groundwater, as the diabase sills and metamorphosed shales are not porous enough to host groundwater. Two aquifers have been identified at the school, an aquifer at ~50 m depth with a shallow circulation system age of ~49 years and a deeper aquifer at ~162 m with a closed circulation system hosting water older than 60 years. It is possible that the syenite dyke to the west of the school may compartmentalize the aquifer system. Preliminary resistivity and gravity data collected in 2009, 2010 and 2011 demonstrate significant variations between the end of the dry season and the end of the rainy season. |
