Assessment Of Non-point Source Pollution In Lake Awassa Watershed Using The Annualized Agricultural Non-point Source (annagnps) Model

Lake Awassa watershed is a Closed-watershed located in the Central Main Ethiopia Riftrnvalley (MER). Despite its ecological, social, and economical functions and values, thernlake and its watershed have been and being inflicted by non-point sources of pollutionrnassociated with deleterious anthropogenic activities. Better management of thernenvironment to halt the existing problem of pollution and possibly to restore thernecosystem, requires informed decision on the root causes of the problem as well as onrnalternative management measures.rnIn this study, the Annualized Agricultural Non-Point Source (AnnAGNPS) model hasrnbeen used for relative assessment of non-point source pollution, prioritization of thernsources of pollution and formulation and evaluation of alternative managementrnmeasures.rnThe relative comparison of the AnnAGNPS model average annual output, with respect tornland use, for the year 2004 showed that cultivated land with Maize and Coffee, monocroppedrnMaize land, and Bare land are leading sources in terms of runoff yield. Inrnaddition, Bare land, Pasture poor condition and mono-cropped Maize land are toprnyielding in terms of sediment. Based on nutrient yield mono-cropped Maize land,rncultivated land with Maize and Coffee, and cultivated land with Maize and ‘Chat’ arernprincipal sources in terms of Nitrogen. Bare land, Shrub land with poor condition, andrnPasture poor condition are leading in terms of Organic Carbon. Mono-cropped Maizernland and cultivated land with Maize and Coffee are chief sources in terms ofrnPhosphorous. Accordingly, the study identified mono-cropped Maize land, Bare land andrncultivated land with Maize and Coffee as priority areas that need alternativernmanagement option to control the non-point source pollution.rnThe study also showed that a change from mono-cropped Maize land to mixed cultivationrnof Maize and ‘Chat’ would result a decrease up to 78% for water and Organic Carbon,rn91% for sediment and more than 95% for Phosphorus yields, while Nitrogen yield remainrnunchanged. A change from Bare land to mixed cultivation of Maize and ‘Chat’ wouldrnresult a decrease up to 99%, 94% and 78% for sediment, Organic Carbon and waterrnyield, respectively, while an increase up to 100% for Nitrogen. A switch from the mixedrncultivation of Maize and Coffee to mixed cultivation of Maize and ‘Chat’ would result arndecrease up to 81%, 75%, 60% and 35% for water, Nitrogen, sediment and Organicrncarbon yield, respectively, as well as a decrease of more than 85% for Phosphorus yield.rnComparison of 1965 and 2004 scenarios showed that a decrease of watershed runoff byrnabout 28%, while there is a decrease of sediment yield by about 73%. Similarly, therernwere a decrease of around 32%, 50% and 35% for Nitrogen, Organic Carbon andrnPhosphorus yields, respectively, for the 1965 scenario from that of 2004.rnThe result of the study showed that a change in land use system can bring aboutrnsignificant reduction in non-point source pollution and the spatial distribution of areas inrnthe watershed that need immediate attention

Get Full Work

Report copyright infringement or plagiarism