SSESSMENT OF WATER QUALITY OF EJERSA RIVER USING PHYSICO CHEMICAL PARAMETERS AND BENTHIC MACRO INVERTEBRATES IN WOLISO TOWN, OROMIA REGIONAL STATE, ETHIOPIA

Abstract

The level of water pollution and ecological disturbance of Ejersa river was assessed using physico-chemical parameters and benthic macro-invertebrates. Ejersa river which is part of the Omo-Gibe basin is used for various activities such as irrigation, washing and cattle watering. But it is exposed to wastewater discharge from municipal sewage, nearby prison institution and abattoir. Three sites selected randomly at upstream as site one, at the back of prison institution in middle of the town was site two and below abattoir at exit point as site three along the river during the period of March to May 2016. Eleven physico-chemical parameters were assessed. Moreover, macro invertebrates were also sampled using D-frame net and identified to the family level. There was significant difference in most of the physicochemical parameters between site one, site two and site three (p<0.05). For instance higher value of phosphate (2.626 mg/L), pH (8.8), nitrate (163.7mg/L), salinity (227.53mg/L), turbidity (246.2 NTU) and electrical conductivity (378.2µs/cm) were recorded at site two than site one and site three. A total of fourteen families (325 macro-invertebrates) belong to six orders were identified during the present study. Chironomidae the most dominant in site two (69.5%), site three (66%) and site one (54.7%), followed by syrphidae (21.9% and 23.3%) in site two and three respectively. Dytisidae was found in site III (6.7%), site I (5.98%) and site II (0.95%), the one that present in all sites. The Shannon-weaver community index showed that the family abundance was higher in site one (4.3) than site two (2.5) and site three (2.6). The waste water discharges from municipal sewage, prison institution, anthropogenic activity and abattoir has been a direct impact on aquatic life, urban and rural communities living near to the river. Physico-chemical parameters were increases with disturbance which leads to poor water quality whereas macro invertebrate assemblage decreases.