Worldwide various type of dams are used to create reservoirs for multiple purposes. Particularly in usual cases, a single dam type is used to form a watertight barrier. Keeping safety and finance in mind, less challenging dam locations, that concerns with aspects like foundation conditions, seismicity at the dam sites, availability of construction materials, etc. are preferred. Ironically, where there is a demand for a reservoir, a suitable dam location is not always available. In those cases, these circumstances make advanced design of dam structures indispensable. An example of such a dam design is the Lower Kaleköy composite dam structure. The same consists of a roller compacted concrete gravity dam at the right bank, which is linked with one of the world's highest deformation joint to the very first asphalt core embankment dam in Turkey, situated on the left bank. The Lower Kaleköy Hydroelectric Power Plant (HEPP) constructed and operated by Kalehan Genç Enerji Üretim A.Ş. with an installed capacity of 500 MW, as part of the Beyhan Kaleköy HEPP cascade is located on the Murat River, a tributary to the Euphrat River in Eastern Turkey. This paper summarizes the design methodology developed by the design consortium (AFRY/Temelsu), headed by AFRY, for the tailored composite dam.