Computer models are becoming increasingly important tools in every environmental managementrnaspects. A general one dimensional water quality model has been developed for one of the mostrnindustrially concentrated and polluted river in Ethiopia; the Little Akaki River. The study covers arntotal of 27.4 km length along the river where pollution issues are significant. The spatial andrnseasonal variation of hydro-geometric properties that affect mixing and transport of chemicals in thernriver were estimated by correlating the river hydro-geometry in a power law model. For this 20rnlocations were systematically selected and field data was collected at five different months. The riverrnhave been conceptualized as 1370 equal length completely mixed computational elements; and arnfunctional representation that includes mass transport and hydrodynamic equations were written forrneach computational elements. The general one-dimensional model equation was solved using thernnumerical technique by finite volume spatial discritization and finite difference temporalrndiscritaization. A computational solution procedure was prepared by writing a computer program inrnMATLAB platform (version 7.0). The result from the model was first verified by comparing it withrntheoretical expectations. BOD and -DO were selected as water quality indicators and thernlongitudinal dispersion coefficient of the river and the kinetic parameters that affect fate of DO andrnBOD in the river were calibrated. The model is in good correspondence with . The performance ofrnthe model in predicting calibration data was satisfactory. After calibration the performance of thernmodel in predicting data not used during calibration was also estimated and the result was in goodrnagreement with these targeted water quality data. The applicability of this model as decision makingrntool for pollution control activities was also assessed and the result is encouraging.rnRecommendation; which takes into account the existing water quality problem in the study area,rnhave been suggested for improvement and wider application the model. As works like this are anrnopen ended; recommendations have been also given for additional research works