Browsing by Author "Seifu, Leulseged Abayneh"

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    Development of semi-distributed physically based hydrologic model for Usangu fans.
    (University of Dar es Salaam, 2000) Seifu, Leulseged Abayneh
    A semi-distributed physically based hydrologic model is developed to simulate the process of wave propagation from the high catchment over the fan-shaped catchment of Usangu plains and estimate the outflow from the fans into the swamp. The model is developed based on the propagation of flow wave from the high catchment on the fans as a function of state space conditions that includes daily state of soil moisture, rainfall and other meteorological conditions of the fans. Implicit finite difference scheme of kinematic wave equation coupled with state water balance equation was used. An alternative model, which is based on the USDA-SCS Curve Number technique, is also developed for the purpose of model output comparison. Both models were applied to the Usangu fans that do not have definite river channel. The input data to the models include rainfall, the inflow from upper catchment, potential evapotranspiration, topographic and soil-water parameters. Since there is no observed flow data at the outlet of the each fan, calibration of the model is impossible. Therefore, an attempt was made to derive the representative physical parameters for each of the fan from various sources. The result obtained from both models show that there is a considerable amount of water loss within the fan. However, the SCS model over estimates the loss as compared to the kinematic wave model. For those fans, which have definite river channel, only channel routing model was applied. The channel flow routing model is developed based on the Muskingum-Cunge method with lateral inflow. It is coupled with the kinematic wave model.