Leader of opposition,  Mr.Raila Odinga has labelled the project “secret tunnels of death” warning that the disruption of water flow in the rivers that feed into River Tana could turn Murang’a, Garissa, Ukambani and Tana Delta regions into deserts.

At a cost of Sh6.8 billion, Raila says the project targets seven key rivers. “All of them feed the River Tana, which is the source of livelihood for communities in Ukambani, Murang’a, Garissa, Tana River and north Mathioya,” he said. He alleged that the project would turn the four regions “into a desert in five years” after implementation.

Others who have raised concern include the late former Environment minister John Michuki and the Muranga County Assembly.

The Government however says the project is safe and will add the much needed water to Nairobi City. But what is the truth? Here is the full report to help you decide.


Nairobi City is the international, regional, administrative and economic hub for Kenya. The city generates approximately 60% GDP. Nairobi, the capital of Republic of Kenya, is facing chronic water shortage including its surrounding area. This is because the proposed additional water source, the Northern Collector Scheme, was not implemented as proposed in 1998. The scheme was initially planned as part of Third Nairobi Water Supply Project. The target year for implementation of the Northern Collector Phase 1 was year 2010. The expected average production capacity of the now proposed Northern Collector tunnel Phase 1 project is 1.6m3/sec (140,000m3/day) with 84% reliability. The safe yield at Ndakaini dam will however be 1.24m3/ day with a 90% reliability.

The present water deficit in Nairobi City is 125,000m3/day. In line with the National Development Plan, Vision 2030, the Government of Kenya has prioritized improvement of water services in Nairobi City and the surrounding areas. To achieve this objectives the Northern Collector Tunnel Phase 1 project is a priority project.

Project Definition and Scope

The NCT 1 project is located along the eastern fringes of the AberdareConservation Area approximately 60 km North of Nairobi City. The works are located in Kangema and Kigumo Sub-Counties of Muranga County.

The project involves:

  • Construction of river intake structures at Maragua, Gikie and Irati rivers
  • Construction of access adits at Gikigie, Irati and Kaanja;
  • Construction of 11km long, 3.0 diameter main water tunnel from Maragua intake to Githika outfall. The tunnel will be fully concrete ined.  A valuation roll completed in December 2015 indicates that 221 people currently live on top of the tunnel.

The other program components involve:

  • Construction of high level Water Treatment Plant at Kigoro and the water transmission pipelines to Nairobi City of capacity of 140,000m3/day
  • Construction of Muranga and Kiambu County community water supply projects to ensure water supply to host communities is also improved.
  • Construction of Nairobi city water distribution network to ensure equitable distribution.
  • Improvement of water services in Nairobi Satellite towns within Kiambu and Kajiado Counties.

Environmental and Social Impact

A consultative environmental and social impact assessment for the project was undertaken. The ESIA study report defined the probable project impacts and mitigation measures. A detailed Environmental Management Plan has been developed and a Monitoring plan drawn. Modalities of ensuring compliance with the Environmental Management Plan have been put in place. Notable areas include

The detailed design for the Northern Collector Water Transfer Project phase 1, has considered all findings of the hydrological and ecological studies to ensure that the project shall neither result in low river flows nor divert water during low river flow seasons. The flows used for the design are such that the environmental and ecological requirements as defined by Trout Fish habitat, downstream water rights and compensation flow as a whole are guaranteed.

The river flow data for the previous 40 years for each of the rivers was obtained and analysed in the hydrological study. The ecological requirements have been defined following analysis of ecological evidence for all flora and fauna including Trout fish. The reserve flows for the three rivers have therefore not only been defined as per the Water Resource Management Authority (WRMA) guidelines but also the findings of these analytical studies. Cumulatively the reserve flows for the three rivers adopted for design is 141,696.00 m3/day against the WRMA standard definition of 93,744.00 m3/day.

The design of the intake structures is such that an unregulated compensation flow channel is provided for at an invert level lower than the tunnel invert level to ensure water only gets into the tunnel after the reserve flows for current/future downstream users and river environmental flows has been released. That means the NCT will not have impact on the frequency of rivers experiencing low flow conditions or drying up, because before these conditions occur, the abstraction will automatically stop because water will only flow through the unregulated compensation flow channel into the river and not into the tunnel which is at a higher level. Certainly as per the design they will be absolutely no abstraction during low river flows.

Downstream water rights and Future demand In the calculation of downstream water needs, the abstraction capacities of all existing downstream consumptive demands which include domestic, industrial, irrigation and other miscellaneous abstractors which are distributed along the river profiles were taken as occurring at the proposed NCT1 intakes. Details of the existing and planned water abstraction capacities, including information on current irrigation and hydro-power projects within the river systems, were obtained from WRMA offices and abstraction licences, Water Service

Providers in Murang’a County as well as design reports obtained from Tana Water Services Board (TWSB). A minimum factor of safety of 1.2 was then used in carrying out the water balance analysis.

Although Section 32 (2) of the Kenyan Water Act, 2002 states that “the use of water for domestic purposes shall take precedence over the use of water for any other purpose…” the potential impact of the project on existing hydro-power generation schemes was also studied. The cumulative impacts of the project on existing hydro power generation was found to be a reduction of 2.32% of the Mean Annual Inflow to Masinga reservoir.

Abstraction of Flood Water

As per the design philosophy of the intake structures explained in (a) above it’s clear that the Northern Collector Tunnel Project will mostly abstract flood waters. This will help in mitigating the negative impacts of flooding downstream and related landslides.

To ensure that positive impacts such as irrigation and storage reservoirs downstream and other water uses during heavy rains are not jeopardized, the Northern Collector

Tunnel Phase 1 project design has been restricted to cumulatively abstract only 43% of the maximum flood waters leaving 57% available for investments in storage infrastructure. From drainage patterns, the average maximum flood water at the three rivers abstraction points is 1,198,368m3/ day, NCT1 will abstract 513,388 m3/ day. Since existing and known plans for future irrigation schemes were considered in defining the compensation flows, this covers any other future and unknown possible abstraction. Further, the balance of flood passed downstream of the weirs of about 684,980 m3/day is expected to increase downstream due to increase in water shed

Feasibility and Validation of 1998 Project Proposal

A number of studies have been carried out on the Northern Collector System, which have involved detailed data collection and analysis to assess its viability.

The initial studies are documented in Feasibility Reports of 1998, carried out by M/S Howard Humphreys and Partners Ltd under the Third Nairobi Water Supply Project. The 1998 report investigated to greater detail the technical and economic viability of the Northern Collector Scheme as a source of water after Ndakaini Dam. The report recommended implementation of the Northern Water Collector Tunnel Phase 1 project by the year 2010. Due to funding challenges the project was not implemented as planned.

In the year 2012, Athi Water Services Board through Egis/MIBP JV carried out the Feasibility Study and Master Plan for Developing New Water Sources for Nairobi and Satellite Towns. This study validated the 1998 report and further recommended implementation of the Northern Collector Tunnel project.

Additional hydrological reviews for the project were undertaken by M/s GIBB Africa as part of the ESIA Study process further validating the hydrological and ecological viability of the project