ASSESSMENT OF SPATIO-TEMPORAL WATER QUALITY STATUS OF LAH RIVER, FINOTE SELAM, ETHIOPIA

Abstract

River water is contaminated by both natural and anthropogenic activity, like waste generated from urban areas and agricultural lands. The study aimed to assess the spatiotemporal water quality status and apportionment of potential source of pollution in Lah River, Finote Selam, Ethiopia. Irrigation water quality indexes were used to determine the suitability of the water for agricultural use. Besides, principal component analysis and PMF receptor model were employed to determine the possible sources of pollution in the Lah River. The concentrations of BOD5 ranged from 10.4 mg/L to 32 mg/L during the wet season and 3.15 mg/L to 15.6 mg/L during the dry season. The mean values of PO4 3- varied from 0.24 mg/L to 0.82 mg/L and 0.102 mg/L to 0.36 mg/L during rainy and dry seasons, respectively. During the wet season, the average values of NO3 - ranged from 10.1 mg/L to 30.2 mg/ L, and during the dry season 1.35 mg/L to 6.61 mg/L of NO3 - were measured. The average values of SAR, RSC, PS, KI, MR, Na%, and PI are 1.07 meq/L, -0.52 meq/L, 0.8 meq/L, 0.78 meq/L, 43.01%, 42.95%, and 63.46%, respectively. The calculated irrigation water quality index shows that the river water quality was appropriate for agricultural use at all sampling points during the dry season. PCA identified two potential sources of pollution during the wet season (domestic and natural and domestic and agricultural) and three factors in the dry season (domestic, domestic and natural, and natural source of pollution), which explain 79.875% and 73.47% of the total variance, respectively. PMF model predicted quite well with Signal to Noise ratio (S/N) >2 and a residual error between -3 and 3 for both seasons. This study suggests that the Lah River is highly polluted due to the entering of domestic sewage and agricultural wastes. So, proper waste management should be adopted to control the continuous contamination in water quality