Tana River (Kenya)

Tana River (Kenya)

The 1,000 kilometres (620 mi) long Tana River is the longest river in Kenya, and gives its name to the Tana River District. 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. It passes through the towns of Garissa, Hola and Garsen before entering the Indian Ocean at Ungwana Bay, at the end of a river delta that reaches roughly 30 km upstream from the river mouth itself.

Annual flow is above 5,000 Mm3 on average, but varies substantially both within and across years, and includes two flood seasons each year. Between 1944 and 1978, average total flow (at Garissa) was 6,105 Mm3, varying from only 1,789 Mm3 in 1949 to 13,342 Mm3 in 1968. During the 1982-1996 period, annual flow remained above 5,000 Mm3 as well. A series of hydroelectric dams have been constructed along the river, including the Kindaruma Dam in 1968, the Kamburu Dam in 1975, the Gitaru Dam in 1978, the Masinga Dam in 1981, and the Kiambere in 1988. A 2003 study reported that two-thirds of Kenya's electrical needs were supplied by the series of dams along the Tana River.