Libyan national plan (LNP) to resolve the water shortage problem will be illustrated through a quartet of a series of papers. The first series of papers (1) will deal with Great Man-Made River (GMMR) supplied from rich ground water reservoirs located in the southern desert regions. This paper (Ib) will conduct the cost analysis study by considering the influence of interest rates on capital costs, as compared to the first paper (Ia) which neglected the effect of interest rates and treated capital costs as sunk value. This will improve the ability to analyze the viability and feasibility of this mean in comparison with other means to resolve the water shortage problem.