CHEMICAL COMPOSITION OF RIVERS AND LAKES 



G33 



Table 59.- — Analyses, in milligrams per liter, of water from East African lakes 



[All analyses except D are from Beadle (1932, p. 207). Except for the silicate and phosphate, all the analyses were carried out by the Government Chemist, London. Analysis 



D is from Beauchamp (1954, p. 27)] 



1 Includes carbonate. 



A. Lake Naivasha. 



B. Lake Baringo. 



C. Lake Rudolf. 



D. Lake Rudolf, Jan. 17, 1953. 



E. Crater Lake A. 



F. Lake Hannlngton. 



G. Lake Nakuru. 



H. Shire River (outlet of Lake Nyasa) at Nchalo, Nyasaland, Nov. 1953. 



The swamps of East Africa are very effective in 

 removing dissolved material from the waters flowing 

 through them. Compare, for example, analyses B 

 and C of table 58. Sim6n Visser (oral communication, 

 1960) concludes, from the amount of pH change, that 

 part of the removal is by ion exchange and part by 

 adsorption. 



The potassium content of some Uganda waters 

 seems very high. The analyst was aware of this 

 anomaly and checked his method carefully for errors. 

 If further work substantiates this high potassium con- 

 tent, it will pose an interesting geochemical problem, 

 particularly as even Kampala rainwater (Simon Visser, 

 oral communication, 1960) contains as much potassium 

 (1.7 ppm) as sodium. 



Parts of Africa have a heavy rainfall on old weathered 

 rock surfaces with extensive swamps to purify the rain- 

 water after it falls. The result can be a very dilute 

 water indeed. Some of the Rhodesian lakes in table 60 

 have less ionic material than silica, while the stream 

 near Nabugabo (table 58, analysis J) must be almost 

 the most dilute surface water in the world. Its 

 conductivity is only 7.5 micromhos — one-quarter that of 

 Kampala rain. 



A few analyses for waters of Somalia are presented in 

 table 61. Most of these analyses are for samples that 

 were collected in the rainy season. In the dry season, 

 as the January sample from the Uebi Scebeli shows, the 

 streams of Somalia are much more concentrated. The 

 seasonal variations in dissolved solids, however, are not 

 as great in the Guiba as they are in the Uebi Scebeli. 

 Notice that sulfate is rather high in these streams, 

 especially in the dry season. 



The streams of Mozambique exhibit a similar 

 variation in content and composition of dissolved 

 materials, as table 62 shows. 



Table 60. — Analyses, in parts per million, of water from Northern 

 Rhodesia and adjacent Tanganyika 



[Analyses are by the Government Chemist, London, and may be found in Ricardo 

 (1938, p. 75)J 



A. Lake Rukwa, Tanganyika, South Basin. 



B. Lake Bangweulu, Northern Rhodesia, open water. 



C. Shiwa Ngandu, Northern Rhodesia. 



D. Lake Chila, Abercorn, Northern Rhodesia. 



Table 61.— Analyses, in parts per million, of water from Somalia 



[Data are from unpublished analyses by George R. Wilson of the Amministra- 

 zione Fiduciaria Italiana della Somalia] 



A. Uebi Scebeli at Belet Uen, Sept. 26, 1957. 



B. Uebi Scebeli at Bulo Burti, Sept. 26, 1957. 



C. Uebi Scebeli at Mahaddei, Sept. 27, 1957. 



D. Uebi Scebeli at Agfoi, Sept. 28, 1957. 



E. Uebi Scebeli at Agfoi, Jan. 9, 1958. 



F. Uebi Scebeli at Oenale, Sept. 28, 1957. 



G. Guiba near Ionte, Jan. 16, 1958. 



The dissolved mineral content of the streams of the 

 humid parts of west Africa is much lower than those of 

 Mozambique, as may be seen from most of the analyses 

 of tables 63, 64, 65, 66, 67, 68, and 69. The head- 



