HYDROGEOPHYSICAL INVESTIGATION FOR GROUNDWATER AT THE DAYSPRING CHILDREN'S VILLAGE, SOUTH AFRICA

Over the past 30 years, the water available in boreholes at the Dayspring Children’s Village school northwest of Johannesburg, South Africa has slowly diminished to the point where the school’s viability is threatened. Dayspring fills a critical need in the community as many of the resident students come from disadvantaged backgrounds. The school’s goal is to expand its services but is unable due to low rainfall in the area resulting in a shortage of groundwater recharge. Accordingly, Dayspring’s old borehole is dry much of the year and the new one has contaminated water.

In addition to studying the shortage of groundwater recharge, this site presents an ideal test case for quantifying the effects of clearing invasive tree species. A large stand of eucalyptus and yellow wattle trees has become well established along the property’s perimeter and both species are known to consume large quantities of water. To date no quantitative studies demonstrating the effect of invasive tree removal in small-scale locally recharged ground water systems have been conducted. This test case could result in a blueprint for invasive plant removal throughout southern Africa, thereby helping to alleviate the growing water crisis in South Africa.

The general flow of regional ground water is from the high-standing Magaliesberg quartzites to the north, towards Dayspring which sits on the mapped E-W-striking Silverton shales of the Transvaal Supergroup. Although shales are normally not ideal groundwater targets, mapping numerous local faults, syenite dykes and lithological contacts in the area can aid in understanding the hydrology and possible compartmentalization.

Many types of geophysical and hydrological data, including gravity, magnetic, electromagnetic, seismic, and electrical resistivity, are being acquired to understand the regional geology, seasonal changes and ultimately the impact of the trees on the local hydrology. Initial results have already shown insight into seasonal groundwater recharge and subsurface structural controls.

This project provides an opportunity to educate students in applied hydrogeophysics to better understand how natural occurrences influence local hydrology. Finally, from an international perspective, it establishes collaborative ties between South Africa, Canada, and USA.