Ewaso Ng'iro Catchment 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 catchment 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 catchment namely; Nyandarua, Laikipia, Nyeri, Meru, Isiolo, Samburu, Marsabit, Garissa, Wajir and Mandera.
Map of ENNCA showing counties and Management Units
ENNCA lies in Kenya’s dry corridor with double maxima of rainfall in March-May (long rains) and October-December (short rains). EwasoNg’iro North Catchment 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 catchment and where the rainfall is more erratic temporally and spatially.
The main rivers in ENNCA 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.
Catchment Management Units in ENNCA
The geographical setting of ENNCA required the identification of suitable Catchment Management Units, as groups of catchments that share similar natural resource management issues.
Distribution of ground water resources in the catchment is as illustrated in the map below.