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.