Koka is the only single Reservoir found in the Upper Awash River Basin being utilisedrnboth for Hydropower and Irrigation uses. The current maximum capacity of the reservoir isrnestimated at 1,000 million rrr'. Up to the inlet to the Reservoir, the Upper Awash River Basinrndrains a catchment area close to 11,300 Km2. A number of important schemes found at thernflood prone areas, downstream of the reservoir, are in need of a workable operation rule forrnKoka which can give them some protection against flooding during wet seasons.rnIn this research an operation rule curve is established. The operation rule curve isrnestablished in such a way that all important variables for the hydropower operation and floodrncontrol are optimised subject to the constraints. Linear programming in MS-FORTRANrnlanguage is used to develop the optimisation model for Koka reservoir operation. The dryrnseason water requirements of downstream irrigation schemes are implicitly guaranteed sincernthe optimised rule curve will ultimately lead to a full storage at the end of every wet seasonrnwhich is desirable by those schemes.rnEmphasis was also given on the flexibility of the model to allow adaptive operationrnrules responding to the changing constraints and boundary conditions which are quiternnoticeable in the Koka reservoir system. The Real-Time operation procedure is formulated tornbe used in conjunction with the established rule-curve to enable the reservoir operators tornmake decisions, regarding releases for various purposes, in a considerably shorter period ofrntime (e.g.,daily) using the current hydrometeorological information.rnThe most important component in Real-Time reservoir operation is the Rainfall-Runoffrnmodel. These models enables, for a known rainfall, to predict the expected runoff which is anrnimportant information for the Real-Time operation of the reservoir and for assessing thernpossibility of flood hazards well in advance of its catastrophic consequences. It is, however,rnunfortunate that most models are data intensive that the scarcity of data is the major bottleneckrnin using them. In this research, a rainfall-runoff model is established employing the SCS