The reserve lies on the opposite side of the Ewaso Ngiro River, south of the Samburu National Reserve, and was established in 1948 as part of the Samburu-Isiolo Game reserve. It sits on 131 sqkm of land at an altitude that rises between 850masl to 1,230masl.
Its name is derived from an oasis of clear water located on its western end while its main feature is the champagne ride located in the south east, an ancient lava-terrace. The climate here is dry, hot and semi-arid.
Wildlife spotted in this reserve include grant zebras, reticulated giraffe, African bush elephant, Grevy’s zebra, oryx, gerenuk, African buffalo, lion, African leopard, cheetah and the spotted hyena. Over 365 bird species have also been recorded. The river is home to both crocodiles and hippos. Somali ostriches, which are larger than the Maasai ostrich and more distinctive for their indigo legs and necks, are also found within the reserve.
Along the Ewaso Ngiro is a narrow band of riverine forest that includes flora such as Tana River poplar, doum palm, specimens of acacia elatior. Vegetation includes acacia tortilis woodland, commiphora. Lava rock is seen exposed in some areas, with scattered grass and shrubs. The salvadora persica (tooth-brush tree) shrub provides food to elephants, whilst its twigs are used as toothbrushes by the nomadic Samburu people.