Rivers have been successfully dammed particularly flowing from relief precipitation areas (high emininences) and those from the edge of the Great Rift Valley, such as the Zambezi, well within the Tropics. In most of this belt of southern Africa, a minimum of seasonal rainfall is reliable and farming is possible, though yields struggle to compete with for example the Mississippi basin, even against like-to-like soil fertilisers. During the December solstice (Southern Hemisphere summer), there are 13 hours, 35 minutes of daylight. There are approximately 10 hours, 41 minutes of daylight during the June solstice (Southern Hemisphere winter). See under circles of latitude for information. Therefore, distance between Arctic Circle and Tropic of Capricorn is essentially constant moving in tandem. This wobble means that the Tropic of Capricorn is currently drifting northward at a rate of almost half an arcsecond (0.468″) of latitude, or 15 metres, per year (it was at exactly 23° 27′S in 1917 and will be at 23° 26'S in 2045).

Earth's axial tilt varies over a 41,000 year period from 22.1 to 24.5 degrees and currently resides at about 23.4 degrees. The Tropic of Capricorn's position is not fixed, but constantly changes because of a slight wobble in the Earth's longitudinal alignment relative to its orbit around the Sun. The Northern Hemisphere equivalent of the Tropic of Capricorn is the Tropic of Cancer. The Tropic of Capricorn is the dividing line between the Southern Temperate Zone to the south and the tropics to the north. (Due to the precession of the equinoxes the Sun currently appears in Sagittarius at this solstice.) This is the date each year when the Sun reaches zenith at this latitude, the southernmost declination it reaches for the year. When this line of latitude was named in the last centuries BC, the Sun was in the constellation Capricornus at the December solstice. Less than 3% of the world's population lives south of it this is equivalent to about 30% of the population of the Southern Hemisphere. Its latitude is currently 23☂6′10.5″ (or 23.43626°) south of the Equator, but it is very gradually moving northward, currently at the rate of 0.47 arcseconds, or 15 metres, per year. The Tropic of Capricorn is one of the five major circles of latitude marked on maps of Earth. Its northern equivalent is the Tropic of Cancer. It also reaches 90 degrees below the horizon at solar midnight on the June Solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. Relationship of Earth's axial tilt (ε) to the tropical and polar circles

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