Fetahi, Tadesse (PhD)Mengistou, Seyoum (Professor)Retea, Badatu2020-12-012023-11-092020-12-012023-11-092019-06-06http://etd.aau.edu.et/handle/123456789/23784Aba Samuel Reservoir (ASR) has been degraded by various types of environmental pollution released from domestic, industrial and agricultural activities. This research aimed at evaluating the ecological condition of ASR using water quality and trophic status indices. In situ measurements of physicochemical parameters (DO, Temperature, EC, and pH) were taken from five sampling sites using portable Multimeter. The major inorganic nutrients (NO3-N, NO2-N, NH4, PO4, and TP) were analyzed in the limnology laboratory using APHA methods and microbial analyzed in biomedical laboratory at AAU. Relationships between plankton and environmental variables were analyzed using Principal Component Analysis (CANOCO for Windows 4.5). Water quality indices of ASR calculated using National Sanitation Foundation Water Quality Index (NSFWQI) had overall mean + SE values of turbidity (105.94 + 39.27 NTU), TSS (745.73 + 222.74 mg L-1), pH (7.96 + 0.049), Temp. (21.9015 + 0.29 °C), DO (3.4615 + 0.25 mg L-1), NO3- N (0.25 + 0.015 mg L-1), TP (0.12 + 0.008 mg L-1) and FC (225 CFU 100 mL-1). According to NSFWQI, bad ecological condition of 37.14, WQI was calculated for ASR recorded from all sampling sites. Trophic status index was calculated by Lamparelli (2004) and Cunha et al., (2013) methods proposed for tropical environments. The overall mean phytoplankton biomass as chlorophyll a was (Chl a, 15.08 + 0.94 μg L-1) and Total phosphorus (62.92 + 0.42 μg L-1). Overall ASR WQI is poor and TSI (56.81 _ 61.80) state that sites has TSI values ranging from eutrophic to supereutrophic and that the overall TSI is in the eutrophic category. Lack of industrial and municipal wastewater treatment plants of the Addis Ababa towns and cities in the basin has caused serious pollution to Aba Samuel Reservoir.enAba Samuel ReservoirNsfwqiLamparelliWater Quality IndexTrophic Status IndexThesis