Hydraulics and sediment control characteristics of a bottom intake type irrigation diversion structure | |
| Author | Nyiwala, Kalinga Gabriel Mahemed |
| Call Number | AIT Thesis no. WA-88-22 |
| Subject(s) | Sediment control Hydraulics |
| Note | A thesis submitted in partial fulfilment of the requirement for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | One of the problems encountered in the design of irrigation , hydropower and water supply projects is the decision on the type of the intake suitable for a particular site condition . Bottom intake structures are normally suitable f or diverting water from streams with steep bed s lopes. The irrigation potential plains of Usangu in Tanzania are drained by various rivers flowing from high mountains. During rainy season the rivers carry with them a huge amount of sediment varying in size from silt to boulders. A number of irrigation diversion structures will b e con structed in the rivers within the transitional zone of the mountains and the plains as its topography dictates, thus a need to investigate the suitability of bottom intake type diversion structures in Usage plains arises. A study on both the hydraulic and sediment control characteristics of a bottom intake type irrigation diversion structure was done . This was accomplished by conducting a number of experiments in a model constructed in the laboratory to a scale of 1:20 written different intake configurations. Trash racks made of circular metal rods parallel to the flow direction were us e d. The boundary conditions for the mode l were derived from Mlowo river in Usangu Plains. The results from the experiments s how that the discharge coefficient increases with the increase of the intake weir crest level. The discharge coefficient due to t h e trash rack gross area is less than one and also less than 0.6 which is the conventional value for the free outflow through an orifice. And trash rack opening ratios of 0.5 to 1.00 have no significant effect on the amount of diverted discharge. Finally a recommendation on further investigation on establishing a functional relationship between the diverted discharge and the approach flow parameters with both the trash rack gross area and orifice area using smaller opening ratios is made. From the study it is concluded that a raised bottom intake structure provided with a flushing channel, with a transverse slope upstream of the intake, a 5% trench beds lope and an extended trash rack slope of at least 10% with trimmed river banks o f at l east 30 meters and 40 meters upstream and downstream of the intake structure respectively performs successfully both o n the hydraulic and sediment control aspects. |
| Year | 1988 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Water Resources Research Engineering (WA) |
| Chairperson(s) | Paudyal, Guna N. |
| Examination Committee(s) | Loof, Rainer ;Tawatchai Tingsanchali |
| Scholarship Donor(s) | Food and Agriculture Organization of the United Nations |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1988 |