Characterizing Potential Bacteria Sources And Quantifying Fecal Coliform Loads For The Gilgel Gibe Watershed Using Bacteria Source Load Calculator Tool

Abstract

Bacteria and water are crucial natural resources used in the activities of sustaining lives. However, indecorous management of livestock manures, human excreta, and pet’s feces, were the main sources of fecal coliform bacteria, which can degrade water quality and quantity. These bacteria have momentous role in the cause of waterborne out breaks and changes natural water characteristics through direct dumping of fecal matters in streams and urban and rural storm water runoff. Quantifying and testing of these bacteria in the water bodies was complex, time consuming, and costly. Because of this fact, characterizing potential bacteria sources and quantifying fecal coliform bacteria loads using Bacteria source load calculator is the easiest and cheapest way at watershed level. There is no study in Ethiopia, particularly in Jimma Zone that depicts bacterial source characterization and quantification of fecal coliform bacteria load using BSLC, so that study aims to characterize potential bacteria sources and quantify fecal coliform bacteria loads to Gilgel Gibe watershed using BSLC tool. Different combination of software’s were used; ArcGIS version 10.3, SWAT, origin pro 2016, and BSLC. ArcGIS was used in characterizing of farm and land use and SWAT was used for watershed delineation of the study area. BSLC is used to calculate monthly bacteria land loading & hourly bacterial instream loading through externally generated available input data and literature reference values. 30m×30m Resolution of DEM, land cover land use data, and five consecutive years (2013-2017) of livestock, human, and pet’s population data collected from study area watershed districts of livestock & fishery development office was also used. The current study showed that, the uppermost fecal coliform bacteria source recognized in the study area was cattle’s which accounts (92.7%) 3.42E+18 cfu /year/ animal unit, followed by sheep (3.9%) 1.43377E+17 cfu and the least contributing animal was horse (0.3%) 1.91E+16 cfu. Of the total fecal coliform bacteria (96.5%) 3.58E+18 cfu were loaded to pasture land and the least portion (0.51%) 1.19E+16 cfu were directly deposited to water bodies. The current study concludes that fecal coliform bacterial load is an alarming for nearby surface water. Water quality modeling with laboratory diagnosis has to be done to identify specific species and amounts of instream fecal coliform loads, finally best watershed management shall be required