Turkey is one of the countries with high hydroelectric energy potential, but today only 35% of this potential is functional. This is due to its geographic position at subtropical climate region with upstream of Euphrates-Tigris Basin. In general, classical calculation methodologies are used for hydropower potential assessments. This paper explains the hydroelectric energy policy and potential of Turkey and suggests a more refined calculation method on the basis of hypsographic curve. Furthermore, currently used hydropower potential calculation formulations are revised in detail, and a new calculation method referred to as the energy tree (ET) is explained and applied to actual data from upper Euphrates River main branch, the Murat River. Comparison of the numerical results in terms of relative error indicates that ET yields about 0.4% improvement over the DP and about 6.5% over the SP methods. This means that ET method yields better refined results than the existing methodologies.