About the County
Physical and Topographic Features
The county lies between 914m above sea level (ASL) in the East and 3,353m above sea level (ASL) along the slopes of the Aberdare Mountains in the West. The highest areas in the west have deeply dissected topography and are drained by several rivers. All the rivers flow from the Aberdare ranges to the West, South Eastward to join Tana River.
The geology of the County consists of volcanic rocks of the Pleistocene age and basement system rock of Achaean type. Volcanic rocks occupy the western part of the county bordering the Aberdare’s while rocks of the basement system are in the eastern part. Porous beds and disconformities within the volcanic rock system form important aquifers, collecting and moving groundwater, thus regulating water supply from wells and boreholes.
The topography and geology of the county is both an asset and liability to the county’s development. The highest areas form the rain catchment areas from where most of the rivers draining the county originate. The terrain is dissected creating the menace of landslides and gully erosion. The numerous streams and valleys necessitate the construction of numerous bridges to connect one ridge to the other; construction and maintenance of roads are therefore made difficult and expensive. Soils emanating from the volcanic activity are generally fertile and important for agriculture. The slopes in the rich volcanic soils on the higher altitudes are particularly suitable for tea growing.
The County is divided into three climatic regions: The western region of an equatorial type of climate, the central region with a sub-tropical climate and the eastern part of semi-arid conditions.
The long rains fall in the months of March, April and May. The highest amount of rainfall is recorded in the month of April, and reliability of rainfall during this month is very high. The short rains are received during the months of October and November. The western region, Kangema, Gatanga, and higher parts of Kigumo and Kandara is generally wet and humid due to the influence of the Aberdares and Mt. Kenya. The eastern region, lower parts of Kigumo, Kandara, Kiharu and Maragwa constituencies receive less rain and crop production requires irrigation
The county is divided into six agro-ecological zones. The agroecological zone one consists of the highest potential zones where forestry, tea and tourism industry form the most important economic activities. Agro-ecological zones two and three are the lowlands east of Aberdares and are generally suitable for both coffee and dairy farming. The flatter area of Makuyu division of Maragwa constituency is characterized by arid and semi-arid conditions. This forms the agro-ecological zones 4, 5, and 6. In these zones, coffee and pineapple plantations thrive by irrigation.