The 1,000 kilometres (620 mi) long Tana River is the longest river in Kenya, and gives its name to the Tana River County. Its tributaries include the Thika, as well as several smaller rivers that flow only during the rainy season. The river rises in the Aberdare Mountains to the west of Nyeri. Initially it runs east before turning south around the massif of Mount Kenya. The river then runs into the Masinga Reservoir and Kiambere Reservoir, created by the Kindaruma dam. Below the dam the river turns north and flows along the north-south boundary between the Meru and North Kitui and Bisanadi, Kora and Rabole National Reserves. In the reserves the river turns east, and then south east.