Kızılırmak River
The national park is on the Ilgaz Mountains, a mountain range in the western Black Sea Region. The mountains are bordered in the north by Gökırmak River and in the south by Devrez Creek, forming the hydrographic boundary between the two river basins. The Gökırmak River originates in the northern slopes of the Ilgaz Mountains, and flows in the west–east direction joining Kızılırmak River as one of its main tributaries. Devrez Creek follows the North Anatolian Fault joining also Kızılırmak in the east.