Ndakaini Dam is famous to most of the people in Kenya. It supplies 84 percent of the water used in Nairobi and has its water sources in Muranga County. It serves over 3 million Nairobi residents with clean drinking water. Ndakaini dam is also referred to as Thika dam. The dam is owned by Athi and operated by the Nairobi City Water & Sewerage Company. It was set up in 1988 so as to supply water to the Nairobi City residents. A piece of land, approximately 1200 acres was set for this dam construction.
The Dam construction was undertaken under the Third Nairobi Water Supply Project between 1989 and 1994. The Ndakaini dam construction in Kenya was financed by the World Bank, The European Bank, The African Development Bank as well as the Kenyan government. The estimated total cost of the project stood at Ksh 2 Billion at that time.
The dam occupies 600 acres of land, when full. The dam has a storage capacity of 70,000,000m3 at full storage level of 2,041 meters above sea level and a depth average of 65m. The dam produces 430,000 m3/day of water that is about 84% of total supply of water to Nairobi residents. It is located 80 kilometers north of Nairobi and 40 kilometers west of Thika town in Kenya, on the slopes of Mt. Kenya and is the main source of water supply for the Nairobi Water Company in Nairobi serving most of the Nairobi residents.
Water from the dam is conveyed through a system of tunnels running from the dam, tapping Kiama River and Kimakia River and diverting the flows to Chania River at the Mwagu Outfall. Water is tapped from Chania River at Mwagu and conveyed via a tunnel to the Mataara chamber from where it’s conveyed by pipelines to Ngethu water production plant.
The dam’s catchment area measures 75 square Kilometer. It consists of Kimakia and Gatare Natural forest which form Aberdare Ranges. The main rivers that drain into the Dam from this catchment are Thika, Githika and Kayuyu. Thika drains 50% Githika 30% and Kayuyu 20% of the catchment into the Dam respectively. The area receives ample rainfall of between 2000 – 2500 mm annually.
The dam is approximately 60 meters deep. Nairobi, with its ever increasing population, has been faced with water challenges for a long time. The water shortage crisis in Nairobi was worst before the construction of the dam in 1984.