Environmental Impact Assessment (EIA) System, which embodies the "prevention principle" of the environmental law, is an important tool for environmental protection. This tool has a special importance for Turkey due to its extremely distinctive ecological conditions. Turkish Environmental Law was first accepted by Turkish Parliament in 1983. In order to assign the EIA procedure to the concrete principles, and determine the application rules, the first version of the EIA Regulation was introduced in 1993. It was then revised in 1997 to eliminate the problems arising during practice and provide an efficient application. Later, the EIA Regulation was rearranged again in 2002 within the scope of the compliance studies with the European Union (EU) acquisition. After one year of this arrangement, the regulation was rearranged again but in 2004 and 2008 one more arrangement was made to the regulation. Among the EU harmonization process, one more revision was required and the final version of the regulation became valid in 2014 because of the cancelation of some articles by the Constitutional Court. While all the revisions are useful for the investors, the environmental issues are overlooked. Recently the increasing number of hydropower projects in Turkey further has proved the role and importance of EIA. In this article, the contradictions among EIA and environmental problems in hydropower projects of Turkey especially and developing countries generally are discussed. Moreover, this article aims to reveal the obvious irregularities in EIA applications of hydro projects.