The city of Addis Ababa is suffering from shortage of water - the city is receiving only 48%rnof its demand in 2007; at the same time losing 35.73% of its supply in its distributionrnsystems. Financial, management and technical constraints are the main bottlenecks thatrnhamper the city from satisfying the highly growing needs of its residents while loosing such arnlarge amount of treated water within its system.rnThis Masters Thesis focuses on modelling water supply pressure for leakage reduction in thernmains of Addis Ababa Water Supply System, especially in Rufael and Saint Paul sub systems.rnEPANET modelling software prepared by the Environmental Protection Authority ofrnAmerica is used for the purpose.rnIn so doing, first of all water balance at both city and the stated sub-city levels wasrnconducted to visualize the loss of water and for the purpose of indexing the leakage level, atrntheir respective levels. Water supply for the entire city and water consumption as aggregatedrnfrom individual customer bills was used to evaluate the total water loss at city level and at thernsub distribution system levels, respectively. Finally, potential Environmental effects ofrnleakage in the city water supply system are assessed.rnQuantifying, characterizing and modelling the factors that lead to water leakage in a cityrnwater supply system is by its nature a complex task requiring well managed network andrnreliable data which is scarce in Addis Ababa city water supply system. As a result, crossrnchecking and verification of data was the most significant problem faced during the study.rnThe paper comprises two major parts; namely Leakage Analysis part and Pressure Modellingrnpart. It was found out from leakage analysis part that water leakage in the city was 35.67%.rnThe ILI value was obtained to be 4.74 which is far from an ideal value of 1. Thus, there is arnroom for AAWSA to target for leakage reduction without affecting the current pressurernsystem. Besides, there is similar room for leakage reduction due to excessive pressure atrnsome nodes with pressure above the recommended maximum for leakage of 80m almost allrnthe day as pointed out from the modelling part