Preliminary model of dam design Ilebinrin and Omita stream in Nigeria as a case study.

The importance of accurate preliminary studies is the basis of this work. This work is a preliminary model of a dam design to discover the feasibility of designing and constructing a small dam. The proposed dam is situated below the confluence of Omita and Ilebinrin stream to get maximum flow in a village near Akure town in South-Western Nigeria. Omita stream was found to be perennial while Ilebinrin stream was free flowing during the dry season and the volume of flow increased during the wet season. Population size is pivotal in determining the human water demand. A population projection of 50 years is done for the surrounding population. In addition to the human water demand, the irrigation water demand is calculated based on the evapotranspiration rate and mean monthly rainfall. These water demands ultimately give the total water demand required for the dam design. Water losses due to infiltration, evaporation and sedimentation are all factored in to design the storage capacity of the reservoir. Through observation of the topographic map, the dam axis was traced, and the catchment area was determined from the contour lines by tracing the highest points at both sides of the stream. Due to the empirical nature of the design of small earth dams, the height of the dam is also pivotal in determining the length of the dam. The volume of earthwork required is determined by additionally factoring in both the recommended upstream and downstream slopes. Stability analysis of the slope by Morgenstern-Price method of slices is simulated using GeoStudio software after having put the determined and assumed dam requirements. This simulation is done to determine the different factors of safety for various slip surfaces. The preliminary model is used to quickly check the feasibility of the dam at the site without incurring any significant cost. [ABSTRACT FROM AUTHOR]