INTRODUCTION
Since the 1970s, energy crises have been reported across the world. In Nigeria Chendo (2001) reported that national energy supply is at present almost entirely, dependent on fossil fuels and fire wood. Also, Akinbami (2001) also observed that the total energy consumption in Nigeria comprises of 5.22% of natural gas, 3.05% of hydroelectricity, and 50.45% natural gas, 3.05% of hydroelectricity, and 50.45% of fuel work. Meanwhile, Ozean Journal of Applied Sciences 4(3), 2011 252 Aliyu and Elegba, (1990) indicate that Nigeria possess potential renewable source of energy along her numerous river systems. Indeed, they reported that a total of 70 micro dams, 126 mini dam and 86 small sites have been identified in Nigeria. Despite these enormous resources electricity is still a mirage in every part of Nigeria, indeed, power outages remain the order of the day.
The performances of water dams in Nigeria are still largely below expectation. Evidences of this can be seen in the frequent dam breakages in northern Nigeria, which is partly due to underutilized water resources. Inefficient reservoir operations also partly explain the low hydro power generation in Nigeria. There are evidences that the water resources of these dams are largely underutilized. The water has not been properly managed probably due to poor reservoir operation guidelines. Inefficiently reservoir management has partially intensified flood problems. Indeed, the problem of inappropriate reservoir operations may worsen an existing situation. Water reservoirs are made to provide multiple benefits, flood control, etc; for water reservoir to fulfill any of these obligations, there is need for an appropriate reservoir management techniques or operation rules. Reservoir operation influences temporal flow patterns, which have implications on water resources management, and also affect healthy riverine ecosystem.
Reservoir operations depend on various optimization approaches. The choice of any optimization techniques depend upon the objective and water resources policy at a given time. Meanwhile, the success of optimization rules will depend on the nature of reservoir element at a given water reservoir. These elements comprise basically the input, throughout an output terms of the reservoir, namely: discharge, reservoir level, reservoir storage balance, inflow, outflow, etc. Reservoir evaporation is the amount of water that is lost within the reservoir, which is computed on monthly basis, discharge is the amount of water that is discharge from the power house, comprising of outflow and turbine discharge. Reservoir level is the average depth of water in the reservoir, it is a measure of the potential energy required in power generation. Storage balance is the volume of water available for generation over a given time. It should be noted that, it is not the total water in storage that are available for use as dead storage is provided to keep sediment off from the power house. Outflow is the water going out of the reservoir; inflow must be commensurate with outflow and reservoir balance. This must be controlled for water to be available for production. Efficient inter play of these element is crucial to sustainable power generation potential of dam reservoir.
This present study will examine the dependence of water level in electricity generation with relative contribution of the reservoir element to power generation.
THE STUDY AREA
Jebba reservoir is located on latitude 9o 35` and 9o 50`N and longitude 4o 30` and 5o 00` E. It located on river Niger, Nigeria. It is a 540mw dam. Jebba is underlain by Basement Complex rocks such as porphyritic granite, mica, quartzite, etc (Sagar, 1985; NEDECO, 1959; Imevbore, 1970). It has an estimated surface area of 303km2 and a volume of 3.31x 109m3. The maximum depth is 105m and a mean depth f 11m (Ita, et al 1984)