The Kerio Valley National Reserve is a protected area in the Kerio Valley, Kenya, a branch of the Great Rift Valley. The 66 square kilometres (25 sq mi) reserve was created in 1983 and is managed by the Kenya Wildlife Service.

The isolated Kerio Valley lies between the Cherangani Hills and the Tugen Hills. The Elgeyo Escarpment rises more than 1,830 metres (6,000 ft) above the valley in places. The valley is 4,000 feet (1,200 m) deep. It has semi-tropical vegetation on the slopes, while the floor of the valley is covered by dry thorn bush. The most comfortable time of the year is in July and August when the rains have ended and the temperatures are not excessive.

The reserve is on the west side of the crocodile-infested Kerio River, while the Lake Kamnarok National Reserve is on the east side. The reserve has dramatic scenery, and prolific birdlife. As of 2006 there were no fees and no facilities, although it was possible to camp in the bush beside Lake Kamnarok. After the reserve was established there was an increase in the wildlife population, including elephants. These caused some damage to neighboring crops and beehives.Most of the people here are Kalenjin herders.

Kerio Valley lies between the Tugen Hills and the Elgeyo Escarpment in Kenya. It sits at an elevation of 1,000 m. in the Great Rift Valley.

The isolated Kerio Valley is situated in a narrow, long strip that is approximately 80 km by 10 km wide at its broadest, through which the Kerio River flows. 4,000 feet (1,200 m) deep, the valley lies between the Cherangani Hills and the Tugen Hills. The Elgeyo Escarpment rises more than 1,830 metres (6,000 ft.) above it in places.

It has semi-tropical vegetation on the slopes, while the floor of the valley is covered by dry thorn bush. The most comfortable time of the year is in July and August, when the rains have ended and the temperatures are not excessive. The Kerio Valley National Reserve has been established since 1983 along the Kerio River to the north of Lake Kamnarok

 

The road from Kabarnet to Iten

The Kerio Valley is the site of elaborate irrigation systems that were constructed during earlier periods of history. These structures are believed to have been built by descendants of theNeolithic Afro-Asiatic peoples who introduced domesticated plants and animals to the Great Lakes region a succession of societies collectively known as the Stone Bowl cultural complex. Most of these early northern migrants are said to have been absorbed by later movements of Nilotic and Bantu peoples. Although the particular irrigation systems in the Kerio Valley are today maintained by the Maraket subgroup of the Nandi Nilotes, the latter aver that they were the work of a northern people of peculiar language called the Sirikwa, who were later decimated by pestilence. According to the Maraket, the Sirikwa "built the furrows, but they did not teach us how to build them; we only know how to keep them as they are."

In Kimwarer in the southern part of the valley, fluoride is mined by the Kenya Fluorspar Company. The southern parts of the valley are settled by the Elgeyo people and the northern part by the Marakwet people. Tugen people live on the slopes of the Tugen Hills. These three groups together with the Nandi and the Kipsigis belong to the Kalenjin people.