The study of sediment problem at Ruvu river intake structure

Ruvu river is the main source of water supply to the city of Dar es Salaam. There has been persistent sedimentation problem at the intake location since its inception. This study tries to find out a way of minimizing the sedimentation problem at the intake by introducing one of the techniques for sediment control. It is apparent that despite the current strong physical and engineering sciences relies more than ever on experimentation. In view of this therefore, a hydraulic model test of the Ruvu river was carried out on how to hydraulically improve the intake structure. Of course, various exclusion and ejection techniques for sediment control are discussed in the literature. The utilization of these methods relies on knowledge of river mechanics concept and the proper analysis of the field data – conditions. Although the various methods discussed have been widely used, quantitative design criteria, in general, does not exist. The successful design of a sediment control structure requires that the engineer considers not only the local effects of the structure, but also the river system and its upstream and downstream response to changes. The key to successful design lays therefore in the application of both sediment and river mechanics concepts. It is hoped that if the modifications are carried out as recommended passed on the results of the hydraulic model investigations, then the situation at the intake location will be improved to an acceptable standard. Also the suggestion of having a second intake though looks unreasonable at present but might turn out to be a long term solution to the shortage of water supply to the fast growing city of Dar es Salaam.