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Kiboriani Hills, the average from 1938-46 was 24 in. (see section 3, Climate and Meteorology). The wet season is from December to April, with an average dry gap" på about a daytoin late January or February The litude 19f othe Region is in general between 3,500 and 4,500 feet above sea level. The topo- graphy is fairly mature, with the beds of former shallow lakes on the south side and scattered inselbergs and granitic outcrops throughout the area. The Kiboriani and Chinene hills, however, have been uplifted, at least in part, in the not too distant past, and this has rejuvenated the topography in their neighbourhood. The main parent rocks range from granitic gneiss to hornblende-gneiss rich in bases. In general, the area is base-rich, and there are extensive lacustrine lime- stone deposits up to thirty feet thick containing small fossil shellfish.
Three main groups of soils occur in the Kongwa Region. From the horn- blende-gneiss is derived a warm red sandy loam of distinctly high fertility which compacts on pressure and on drying. This soil shows no visual difference in profile from the surface to parent rock, which may be as shallow as two feet, but is usually deeper. The more granitic rocks, occurring usually on the crests of the gentle ridges, yield a pallid yellow or buff to grey sandy soil (the upland pallid type) often with iron-stained quartz in the layers immediately above the parent rock. In this soil type, or in a coarse variant of it with small ironstone con- cretions, water holes frequently occur. The third group contains the soils of valley bottoms and lake beds; these are brown to grey and black, and are heavy and often calcareous. Typical chemical analyses are given in section 11. Borehole water in these areas is very hard and somewhat saline.
The main vegetation of the Kongwa Region is a dense deciduous thicket, occurring on the red and upland pallid soils, containing several species of Commiphora, with some Acacia spirocarpa, particularly on drainage lines, and scattered Adansonia digitata (Baobab). Many other species are also present. The thicket, which has been described by Hornby and Hornby (1942) has several distinct communities within it. It is for the most part up to 15 feet high, and is impenetrable except along native paths and cattle or game tracks. Old lake bed areas form open grassy plains with locally scattered tall trees and limited areas of various types of scrub. As in the rest of the areas, systematic botanical work in these interesting communities has not so far been possible.
The presence of numerous overgrown water holes or hafirs, with earth walls -often built up to 20 feet high and of a similar thickness at base (occurring in some areas as frequently as one to every two square miles), and of very large acacias and baobabs, taken together with the reaction of the thicket to clearing and to fire, leads to the belief that the country in the Kongwa Region was formerly more densely populated by a well organised people, and that it was at that time far more open. Whether the thickening of the vegetation is due to overgrazing by the cattle, leading to failure of fire to control regeneration of thicket species, or to the incursion of thicket into areas of former cultivation, is at present an open question.
There is sufficient suitable land in the Kongwa Region for from 15 to 20 units (450,000 to 600,000 acres in all) and possibly more, but the scale of final develop- ment will depend on levels of yield and the state of communications, particularly the capacity of the Central Line railway and the port of Dar-es-Salaam to evacuate the produce.
-Urambo Region, Tabora district, Tanganyika
Urambo, on the Central Line railway, lies about 60 miles west of Tabora in the Western Province of Tanganyika. The altitude is about 3.500 feet, and rainfall in the area (for which there are no previous records) is believed to lie between 30 in. and 35 in. annually, falling from December to May.
The topography is extremely mature and peneplanated. The drainage lines are almost completely filled in and take the form today of wide open grassy or lightly wooded areas, swampy in the wet season, but with little or no flow of water.
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