The thermal springs of Swaziland: a review

The thermal springs of Swaziland and adjacent KwaZulu Natal have, over the years, attracted attention from hydrogeologists, hydrochemists and structural geologists. While some of the springs in Swaziland are well known amenities, others are less well visited and some difficult to access. There are eleven warm springs in Swaziland discharging between 1 and 10 l/s from Precambrian age rocks; all are situated at or near valley bottoms. The springs have surface discharge temperatures of between 25 and 52 oC and total dissolved solids concentrations less than 400 mg/l. In all cases the water is meteoric in origin. Geothermometry indicates that maximum temperatures up to 100 oC are achieved during circulation. If the average geothermal gradient is about 20 oC/km as recorded in a deep mine at Barberton, then this would require circulation up to a depth of several kilometres. However, it is likely that circulation bottoms at about 1 km, as pressure of overburden inhibits dilation of fractures at such depths and the excess temperature may derive from a locally enhanced geothermal gradient. The discharge water is young, with 14C ages of between 4000 and 5000 years.