A Chemical Survey of the Waters of Mount Meru, Tanganyika Territory, Especially with Regard to their Qualities for Irrigation

Abstract

In this paper are presented the results of a number of analyses of water-samples taken during the years 1931 and 1982 from the streams and minor lakes occurring on the slopes of Meru, the dominating mountain of the district of Arusha, Northern Province, Tanganyika Territory. The work originated in the examination at Amani of a few samples from streams on the south-west of the mountain, at the request of Mr. E. Harrison, Director of Agriculture for Tanganyika, who on the occasion of a visit to the area in December, 1930, expressed the opinion that alkali salts, either originating naturally in the soil or introduced by irrigation, were possibly causing injury to coffee, the principal economic crop of the district. It is common knowledge, locally, that the streams draining from Meru contain "soda" in greater or less amount, but in spite of this they have been employed for irrigation, sometimes on a lavish scale. The results of these first analyses made it clear that a systematic chemical survey was desirable if guidance was to be offered on the merits of this practice in the several divisions of the district, and one of us (D.S., in his capacity as District Agricultural Officer, Arusha) began a series of periodical samplings of the principal streams. The analyses were carried out by another of us (W.E.C.) in the soils laboratory at Amani. At a later stage, in view of the relevance of the whole subject to the study of the volcanic soils of the area, it was decided to extend the samplings beyond the range originally contemplated, so as to include all waters rising on the mountain whether or not they came into question for irrigation. This was done during a circuit of the mountain made by D.S. and W.E.C. in company in August, 1932.