Ewaso Ng’iro North Catchment Area (ENNCA) – Nanyuki
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.
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:
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.
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.
Available water resources
The available water resources consisting of the surface water runoff and sustainable yield of groundwater were estimated in ENNCA for the years 2010 and 2030 as follows:
|Year||Available water Resources (MCM/year)|
|Percentage of 2010 values||147%||90%||134%|
– Source: National Water Master Plan 2030
The sustainable yield of groundwater was derived as 10% of the groundwater recharge in the catchment area excluding river courses and riparian areas with a width of 1 km.
The annual water demands for 2010 and 2030 are summarized below.
|Year||Water Demands (MCM/year)|
– Source: National Water Master Plan 2030
Major Land use/ cover types
Forest Areas: Forest areas in ENNCA are mainly in Samburu, Laikipia, Meru, Nyeri, and Nyandarua Counties. These are the major water towers for the catchment and groundwater recharge areas.
o In Samburu County, the forest areas include Mt. Ng’iro, Ndotos Range, and Mathews Range forest reserves.
o In Laikipia County, they are Mukogodo, Lariak, Marmanet, and Rumuruti forest reserves.
o In Nyandarua, they are Uaso-Narok, Leshau, Ol-Bolossat, Bahati, and Abardare forest reserves.
o In Nyeri, they are South Laikipia and Abardare forest reserves.
o In Meru, they are Mt. Kenya, Ndere, and Timau forest reserves; and
o Marsabit forest reserve in Marsabit.
o In Mandera County, Dandu hills forms part of the forested areas and are a source of springs and also act as groundwater recharge zones.
Wetlands and Riparian zones: The wetlands and riparian zones in the catchment are Lorian Swamp in Isiolo and Garissa Counties the wetlands are major groundwater recharge areas for the Merti aquifer.
o Lake Ol-bolosab which is a source of Ewaso Narok river.
o Other swamps of importance in the catchment are Ewaso-Narok in Laikipia county and Suguta Marmar in Samburu county.
Rangelands and Grasslands: Rangelands and grasslands constitute the largest land use areas in the catchment. They are mainly used to provide pasture/fodder for livestock farmers in the catchment.
Open/ Bare land: These areas are dominated by open spaces with very little vegetation or sand deposits for most parts of the year. They are mainly in Marsabit, Isiolo, Samburu, Wajir, Mandera and parts of Garissa County. The major ones being Chalbi and Kaisut deserts.
Cropland: Although the catchment is mainly arid and semi-arid, there are pockets of rainfed croplands. They are mainly in the upper parts of the catchment (in Nyandarua, Laikipia, Nyeri, and Meru Counties) and lower parts in Wajir and Garissa Counties, below the Lorian Swamp, in the flood recession areas.
Major Water Resources Management Challenges
Drought, Water scarcity – Leads to water conflicts (human Vs human and human Vs wildlife), threatened environmental reserve, destruction of aquatic habitat
Floods – Garfasa, Isiolo, Mandera, Ewaso Narok, Wiyumiririe
Climate variability – receding of glacier on Mt. Kenya.
Ewaso Ngiro North river disappearing at Lorian swamp, Hawaye, approx 30 km upstream of Habaswein. This would call for catchment rehabilitation, construction of more water storages upstream for assisting in the regulation of flow of water especially during the dry spell.
Catchment degradation – The bare ground surface in experience accelerates cases of unproductive land, landslides, soil erosion, floods, and siltation of water bodies/dams thereby reducing water holding capacity.
Ground water pollution especially in Wajir, Ngusishi, Nyahururu
High groundwater salinity levels in some areas
Insecurity in some parts of the catchment
Vastness of the catchment and poor road network in some areas
Water use conflicts