Environmental Analysis Of A Hydrologic System The Case Of Tinishu Akaki River Western Addis Ababa Ethiopia

Water Quality analysis of the Tinishu Akaki River System has been carried outrnwith the objective of identifying where and when the river’s pollution and itsrnconsequences are more pronounced. And to determine what factors and / orrnprocesses prevail and control the situation spatially and temporally. To do sornprimary data on conventional water quality parameters; dissolved oxygen (DO),rnammonia (NH3), Nitrate (NO3), Nitrite (NO2), PH, temperature(To) and totalrndissolved solids (TDS) was generated. In this study, five water samples wererncollected and analysed to represent the 2007 moderate flow period, the threernspatial domains of the river (i.e. up, mid, and down streams) and the date whenrnindustrial effluents discharge is minimal. Besides, secondary data on the samernand other physiochemical parameters for the years 1997, 1999, 2000, 2002/03,rn2003/04, 2005/06, were collected from EPA monitoring unit and availablernliteratures. After that, the available primary and secondary data were segregatedrnbetween the three spatial domains, Low, Moderate, and High flow seasons, andrnPeak and little or No Industrial effluents discharge patterns. Then, by takingrndissolved oxygen (DO) depletion as important water quality indicator pollutionrnalong the river course and its consequences have been analysed using spreadrnsheet program. Moreover the physicochemical factors such as altitude,rnatmospheric pressure, temperature, Stream flow velocity, Salinity (TDS), BOD5,rnNH3, PO4, …etc. were used to justify the variation in DO level in the River waterrncolumn. The results of the analyses depict that the extent of pollution is morernsevere when industrial effluents load is high and the river’s flow is low. Moreover,rnthe midstream spatial domain is found to exhibit the worest situation in terms ofrnpollution and or DO depletion. Above all, the increase in the concentrations ofrnpotentially harmful substances; heavy metals (Fe, Mn and Cr), ammonia,rnhydrogen sulphide, sulphates and phosphates is found to be associated with therngenerally declining DO level in the down stream direction. So as to abate thisrnproblem of water pollution, TMDLs (Total Maximum Daily Loads) and WLAsrn(Waste Load Allocations) for oxygen demanding wastes of industrial point sources is suggested to be the most cost effective and applicable mechanism ofrnabatement that can assure the attainment of in stream water quality standards.rnKey Words: Dissolved Oxygen depletion, Tinishu Akaki River, ConventionalrnWater Quality parameters, Ethiopia

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