Effect of Bahir Dar municipal effluents on water quality of the head of Blue Nile River
The study was conducted with the main objective of determining the effect of Bahir Dar municipal effluents on water quality of the head of Blue Nile River. Physico-chemical parameters were measured at seven points, whereas aquatic macro invertebrates were sampled at six sites. A total of 6813 aquatic macro-invertebrate individuals belonging to 30 families were collected. The Shannon–Wiener diversity Index, the Hilsenhoff family-level biotic index, Family richness and percent dipterans were calculated and differed significantly among sampling sites (p < 0.05). Physico-chemical parameter mean values differed significantly among sampling sites (p < 0.05), dissolved oxygen mean value being higher at sampling site (A) and BOD 5 , TDS and conductivity values being higher at (C5). BOD 5 , conductivity and total alkalinity mean values were above permissible levels set for municipal effluents to be discharged to surface water. DO, BOD 5 and total alkalinity mean values at head of Blue Nile River were lower than WHO recommended values for drinking water. The study concludes that the Bahir Dar municipal effluents severely affected the water quality of the head of the Blue Nile River.  Therefore, a municipal waste water treatment system is urgently recommended. Keywords : Bio-monitoring, macro invertebrates, physico-chemical parameters