Ewaso Ng’iro North Basin Area (ENNBA)

Ewaso Ng'iro River passing through the Shaba Park (Picture by Marc Samsom)
Ewaso Ng’iro River passing through the Shaba Park (Picture by Marc Samsom)


Ewaso Ng’iro Basin Area Location lies within :  Latitude S 000 25′ to N 040 29′ and from Longitude E 360 20′ to E 410 55′ . It covers an area of about 210,226km2; it is about 36% of the total area of Kenya 576,000km2. It is the largest of all the six basin areas but with least population, this is because it falls in Arid and Semi-Arid (ASAL) parts of Kenya. Altitude ranges from 150m at the Lorian swamp to 5,199m at the peak of Mount Kenya.

There are 10 Counties covered within the basin namely; Nyandarua, Laikipia, Nyeri, Meru, Isiolo, Samburu, Marsabit, Garissa, Wajir and Mandera.

Counties and Management Units in ENNBA
Counties and Management Units in ENNBA


ENNBA lies in Kenya’s dry corridor with double maxima of rainfall in March-May (long rains) and October-December (short rains). Ewaso Ng’iro North Basin Area has a mean annual rainfall of 411 mm which ranges from over 800 mm in the highlands to less than 400 mm in the ASAL areas which comprise 90% of the total area of the basin and where the rainfall is more erratic temporally and spatially.

Water Resources in the Basin

Surface Water

The main rivers in ENNBA are:

  1. The Ewaso Ng’iro River and its tributaries (Ewaso Narok, Ewaso Ng’iro, Likiundu and Liliaba). Other major tributaries are; Isiolo, NgareNdare, Ngusishi, Timau, Sirimon, Teleswani, Ontulili, Likii, Nanyuki, Rongai, Burguret, NaroMoru, Moyok, Mutara, Ngobit, Suguroi and Pesi.
  2. River Daua which is a Transboundary river. The geographical setting of ENNBA required the identification of suitable Basin Management Units, as groups of basins that share similar natural resource management issues. The management units in ENNBA are Daua, Ewaso Laggas,Lower Ewaso Ngiro, Nundoto, Chalbi, Middle Ewaso Ngiro, Ewaso Narok, Nanyuki and Upper Ewaso Ngiro
Management Units in ENNBA
Management Units in ENNBA

Ground Water

Distribution of ground water resources in the basin is as illustrated in the map below.

Ground Water Aquirer Map
Ground Water Aquirer Map
YearSurface WaterGround WaterTotal
2010 1,725 526 2,251
Percentage of 2010 Values147%90%134%