Mathematical Modeling of Point source Pollutants Transport in the Little Akaki River

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Addis Ababauniversity


Computer models are becoming increasingly important tools in every environmental management aspects. A general one dimensional water quality model has been developed for one of the most industrially concentrated and polluted river in Ethiopia; the Little Akaki River. The study covers a total of 27.4 km length along the river where pollution issues are significant. The spatial and seasonal variation of hydro-geometric properties that affect mixing and transport of chemicals in the river were estimated by correlating the river hydro-geometry in a power law model. For this 20 locations were systematically selected and field data was collected at five different months. The river have been conceptualized as 1370 equal length completely mixed computational elements; and a functional representation that includes mass transport and hydrodynamic equations were written for each computational elements. The general one-dimensional model equation was solved using the numerical technique by finite volume spatial discritization and finite difference temporal discritaization. A computational solution procedure was prepared by writing a computer program in MATLAB platform (version 7.0). The result from the model was first verified by comparing it with theoretical expectations. BOD and -DO were selected as water quality indicators and the longitudinal dispersion coefficient of the river and the kinetic parameters that affect fate of DO and BOD in the river were calibrated. The model is in good correspondence with . The performance of the model in predicting calibration data was satisfactory. After calibration the performance of the model in predicting data not used during calibration was also estimated and the result was in good agreement with these targeted water quality data. The applicability of this model as decision making tool for pollution control activities was also assessed and the result is encouraging. Recommendation; which takes into account the existing water quality problem in the study area, have been suggested for improvement and wider application the model. As works like this are an open ended; recommendations have been also given for additional research works



Little Akakir