Location of the South African Geodynamic Observatory
The South African Geodynamic Observatory (SAGOS) is part of the South African Astronomical Observatory (SAAO), which is located near to the town Sutherland, Northern Cape province, South Africa. A superconducting gravimeter (SG) is installed at the SAAO station on the top of a table mountain. It has the coordinates 20.81 E, 32.38 S and the height above sea level is 1763 m.
The area around Sutherland is semi-arid with mean annual precipitation rates from 300 to 400 mm and the potential evapotranspiration can amount up to 2000 mm per year. The mean annual temperature is 12° C, whereas the daily temperature fluctuation can amount up to 26° C. Sutherland is considered as one of the coldest places in South Africa and snowfall during winter time is common.
The soils are rust red sandy-clayey colluvial soils with a high skeleton content and the thickness varies between 0.2 to 1.0 m. The underlying regolith consists of unconsolidated Doleritic gravels. The table mountain is protected by a Dolerite cap and the underlying sedimentary rocks are sandstones, shales, siltstones and mudstones.
The hydrology is characterised by non-perennial rivers and water flow occurs only during winter time and after heavy rainfall events, whereas thunderstorms are frequently during summer time. The hydrogeology is characterised by a fractured groundwater system, implying a high heterogeneity. For example, the depth of the groundwater table varies between 5 to 100 m. Especially, high yielding aquifers are associated with joint systems and fault zone.