Kiambu County is one of the 47 counties in the Republic of Kenya. The County is a metropolitan County and it’s headquarter is based in Kiambu Town.  The County serves as a residential area for many people from different parts of the country who work in the urban centres especially Nairobi City. The County therefore is inhabited by different tribes of Kenya with majority being Kikuyus.

The County is a member of Central Region Economic Bloc (CEREB) that bring together ten counties drawn from the larger Mount Kenya region namely: Embu, Kiambu, Kirinyaga, Laikipia, Nakuru, Nyandarua, Nyeri, Meru, Murang’a and Tharaka Nithi. The bloc was established through an MoU in February 2016 with the overall goal of harmonizing laws and regulations to facilitate trade and investment, leveraging competitive and comparative advantages and economies of scale to create employment opportunities and incomes, and tap into technology development to expand economic frontiers in the member counties. Consequently, CEREB governors signed an agreement in June 2019 to harness resources in the region for development. The region is known for agricultural activities due to the favourable climatic conditions and the fertile soils. The main aim of this Bloc is to leverage on economies of scale in undertaking joint development projects and activities. Based on the Kenya National Bureau of Statistics data, CEREB is the bloc that contributes the largest share of the Country’s economy at over 26% of the total National Gross Domestic Product (GDP).  Nakuru County contributed the highest GCP of 6.9 while Tharaka Nithi County had the least at 0.9 per cent

The County has huge potential in agriculture and service sectors. A large proportion of the population in the County depend on agriculture thus making it to be the predominant economic activity. Agriculture therefore contributes the largest share of County population’s income and overall Gross Domestic Product in Kenya. Other activities that take place in the urban areas of the County include industrial/ manufacturing activities. The County further has quarrying and mining activities taking place such as in Juja and Thika Sub Counties.

1.2 Position and Size

Kiambu County is located in the central region and covers a total area of 2,538.7 Km² according to the 2019 Kenya Population and Housing Census. It also borders six counties namely Nairobi and Kajiado Counties to the South; Machakos to the East; Murang‘a to the North and North East, Nyandarua to the North West, and Nakuru to the West. Further the County lies between latitudes 00 25‘and 10 20‘South of the Equator and Longitude 360 31‘and 370 15‘East. Figure 1 show the location of the County in Kenya.

1.3.1 Physical and Topographic features

Kiambu County is divided into four broad topographical zones; Upper Highland, Lower Highland, Upper Midland and Lower Midland Zones. The Upper Highland Zone is found in Lari subcounty and it is an extension of the Aberdare ranges that lies at an altitude of 1,800-2,550 metres above sea level. It is dominated by highly dissected ranges and it is very wet, steep and important as a water catchment area. The major forests in the County are also found in this zone, which are Kieni and Kinale with an acreage of 13,723.6 and 10, 504.87 hectares respectively.

The lower highland zone is mostly found in Limuru and some parts of Gatundu North, Gatundu South, Githunguri and Kabete sub counties. The area is characterized by hills, plateaus, and high-elevation plains. The area lies between 1,500-1,800 metres above sea level and is generally a tea and dairy zone though some activities like maize, horticultural crops and sheep farming are also practiced. The upper midland zone lies between 1,300-1,500 metres above sea level and it covers mostly parts of Juja and other sub counties with the exception of Lari. The landscape comprises of volcanic middle level uplands. The lower midland zone partly covers Thika Town (Gatuanyaga), Limuru and Kikuyu sub counties. The area lies between 1,200-1,360 metres above sea level. The soils in the midland zone are dissected and are easily eroded. Other physical features include steep slopes and valleys, which are unsuitable for cultivation. Some parts are also covered by forests.

The county is covered by three broad categories of soils which are: high level upland soils, plateau soils and volcanic footbridges soils. These soils are of varying fertility levels with soils from high-level uplands, which are from volcanic rocks, being very fertile. Their fertility is conducive for livestock keeping and growth of various cash crops and food crops such as tea, coffee, horticultural products, pyrethrum, vegetables, maize, beans, peas and potatoes. These soils are found in the highlands, mostly in Gatundu South, Gatundu North, Githunguri, Kiambu, Kiambaa, Lari, Kikuyu, Kabete and Limuru sub counties. Low fertility soils are mainly found in the middle zone and the eastern part of the county which form part of the semi-arid areas. The soils are sandy or clay and can support drought resistant crops such as soya beans and sunflower as well as ranching. These soils are mostly found in parts of Juja, Thika Town, Ruiru, Kikuyu, Limuru, Gatundu North and Gatundu South sub counties.

Most parts of the county are covered by soils from volcanic footbridges. These are well drained with moderate fertility. They are red to dark brown friable clays, which are suited for cash crops like coffee, tea and pyrethrum. However, parts of Thika Town, Ruiru and Juja sub counties are covered by shallow soils, which are poorly drained, and these areas are characterized by low rainfall, which severely limits agricultural development. However, these areas are suitable for ranching and growth of drought resistant crops.

Climatic conditions

The county experiences two rain seasons: the long rains season runs between March and May and is wetter than the short rains season experienced between October and December. Dry spells (periods with less than 20 mm rainfall) occur between July and September. This season is also cooler characterised with drizzles and frost in some parts of the County. April receives the highest rainfall, more than 200 mm.  The annual average precipitation in the county is 600-1300 mm. The northern region receives an annual average precipitation of more than 1000 mm. Historical annual average rainfall and temperature records show a directional-spatial trend, with peak values generally appearing in the northern parts of the county for precipitation and western parts of the county for temperatures.

The annual average temperature for the county is 15-23°C. The western areas of the county including the upper midland and the lower highland agro ecological zones experience annual average temperatures greater than 20°C.  Lowest temperatures are recorded in the months of June to August whereas highest temperatures are recorded in the months of January to March. The county‘s average relative humidity ranges from 65 percent in February which is generally a hot month and 84 percent in the wet months of April and May.

1.3.3 Ecological conditions

Kiambu County covers a wide range of agro ecological zones based on the climatic characteristics. These are upper highland humid and semi humid; lower highland humid, semi humid and sub humid; upper midland humid, semi humid and sub humid; lower midland humid, semi humid and sub humid; lower midland transitional and upper midland transitional, among others.

The upper highland humid agro ecological zone covers the upper parts of Kiambaa and Limuru; Kikuyu sub county falls in the lower highland semi humid zone; Gatundu North and Gatundu South sub-counties found in the upper midland sub humid agro ecological zone. Small land holdings as well as small scale farming are mostly found in these areas.  The large land holdings are especially found in Juja sub-county which is in the upper midland transitional agro ecological zone and the upper highlands in Limuru and Lari sub-counties in the upper highland humid zone.

The County has both surface and ground water resources. The county is divided into several sub-catchments areas. The first one is Nairobi River Sub-catchment which occupies the southern part of the county with the major rivers being Nairobi, Gitaru, Gitathuru, Karura, RuiRwaka, and Gatharaini. The second one is Kamiti and Ruiru Rivers Sub-catchment which is located to the north of the Nairobi River sub-catchment. It has eight permanent rivers which include Riara, Kiu, Kamiti, Makuyu, Ruiru, Bathi, Gatamaiyu and Komothai.

The third one is the Aberdare plateau that contributes to the availability of two sub-catchments areas comprising of Thiririka and Ndarugu Rivers. The main streams found in the two areas include Mugutha, Theta, Thiririka, Ruabora, Ndarugu and Komu. They flow from Nairobi, Kamiti, Ruiru, Thiririka, and Ndarugu sub-catchments to form Athi River sub-catchment. The fourth is the Chania River and its tributaries comprising of Thika and Karimenu Rivers which rise from the slopes of Mt. Kinangop in the Aberdare ranges. The last one is Ewaso Kedong sub catchment which runs in the North-South direction and occupies the western part of the County. It has several streams that normally form swamps such as Ondiri and Nyakumu swamps in Kikuyu subcounty.

The eastern part of the county that includes Thika, Gatundu, Ruiru and Juja is well endowed with surface water from Chania, Thika, Karimenu, Ruabora, Ndarugu, Thiririka, Theta, Mukuyu, Ruiru rivers.  The western part of the county that includes Limuru, Kikuyu, Kiambu, Karuri, Lari and Githunguri areas has limited surface sources, hence rely on underground water sources mainly boreholes.