BURA GRAVITY: A FIRST OF ITS KIND IRRIGATION PROJECT IN KENYA
The Bura Irrigation and Settlement Scheme Rehabilitation Project, which is under construction, is planned to transform lives and advance irrigated agriculture in Tana River County. We sat down with the project manager, Eng Joseph Karangu Wairore, for its details, execution, and timelines.
He has a Master’s degree in Civil Engineering from the University of South Australia, post-graduate diploma in Hydraulic Engineering in River Basins from Hydraulic Research Institute- Cairo and a Bachelor’s degree in Agricultural Engineering from Egerton University.
Eng. Karangu has more than 25 years of engineering experience and has worked with the Ministry of Water, Land Reclamation and Rural Development, Ministry of Water and Irrigation, Water and Flood Water Management and now the National Irrigation Authority as a Principal Irrigation Engineer.
How was Bura Irrigation and Settlement Scheme Rehabilitation Project conceptualised?
Bura Irrigation and Settlement Scheme was initiated by the Kenya Government in 1978 and was completed in 1981. At inception, the schemes irrigation infrastructure comprised of a temporary pumping station at Nanighi with four pumps with a total discharge of 5.8 m3/second, a sedimentation basin, 50km main canal, 11km branch canals and 10-night storage reservoirs capable of irrigating 12,000 acres.
The scheme produced food crops and high quality cotton between 1982 and 1989 when the scheme irrigation water supply became irregular and unreliable affecting the expansion and sustainability of the scheme.
The government with the assistance from Kuwait Fund for Economic Development (KF) commissioned a study in the 90s with the aim of identifying the challenges affecting scheme. The study identified high cost of operation and maintenance of the scheme as the major challenge affecting the reliability of water supply to the scheme. This was attributed to the use of pump-fed system that requires fuel whose price is ever increasing, routine maintenance of the pumps and replacement of the same after the expiry of their life span. These cost severely strained the available scheme recurrent budget.
The study recommended upgrading of the irrigation scheme from pump-fed irrigation system to gravity-fed system and increase the amount of abstracted water from the current 3m3/second to 11m3/second to allow reliable irrigation of 25,000 acres. Hence the Bura Irrigation and Settlement scheme rehabilitation project.
This would be achieved through Construction of Korakora gravity Intake, including protection works, construction of new conveyance system from Korakora to Nanighi: 26km long from the new intake site to join the existing main supply canal and Rehabilitation of existing irrigation infrastructure. This is the Bura Irrigation Rehabilitation and Settlement Project.
When did the construction start?
After completion of the project’s feasibility study and thorough design in 1990s, construction works started on May 27, 2013.
Any challenges encountered along the way thus far?
Yes, the works commenced on May 27, 2013 and were expected to be completed on November, 26, 2015. Due to valid reasons initially, notably interference by the community during construction citing land and employment of locals, inadequate GoK counterpart funding to meet the 70:30 GoK to donor financing ratio and delay in approval of master list, the contract completion date was extended to March 31, 2018. Nevertheless, the rate of work progress by the contractor was slow even after these issues were resolved and he only achieved 31 percent by the time of the contract termination on May 2018 due to him being declared bankrupt.
How did you bounce back from that?
After termination of the contract and in order to expedite the achievement of project objective, the project co-financiers (Arab Co-ordination Institutions Joint Supervision Mission) (KF, OFID, Saudi Fund for Development (SFD)), State Department of Irrigation and NIA agreed to have the initial works packaged and executed in three phases comprising of:
i. Phase 1: Sheet piling and associated Korakora Intake
ii. Phase 2: Completion of new main canal, its hydraulic structures and the associated civil works
iii. Phase 3: Rehabilitation of existing irrigation infrastructure
NIA procured two contractors Afrikon Ltd and Tunasco Insaat Anonim Sirketi in Joint Venture with Marsh Construction Company Limited and Marfa Construction Company Limited to undertake phase one and two respectively of the pending works.
Please walk us through the project’s components?
This project entails the construction of the Korakora gravity intake, which includes submerged weir, diversion canal, head regulator and sedimentation basin. The second phase, construction of the new supply canal from Korakora to Nanighi is 26km with the following components, canal excavation and lining, construction of service road, the dyke and associated civil works such as runoff crossing culvert, bridges, road crossing and animal watering points.
What is an intake?
An intake structure is a transition through which flow is diverted from a source, such as a river, reservoir or the ocean, into a conduit, which may be a canal or a pipe. It consists of a diversion canal, head regulator and a siltation basin.
A sustainable intake should be user-friendly and designed to perform three essential tasks. First, the intake should provide water at the right head. The elevation of the intake site should provide adequate head for water to flow from the intake to irrigation commands and have extra head to allow for water application to the farms.
Second, it should provide adequate quantity of water to meet the scheme water demand at all times, even when river flows are low. For the case of Bura Irrigation Scheme, the peak water demand is estimated as 11 cubic metres per second.
Third, the intake is expected to provide water at the right quality. Given that River Tana is highly silted, the intake should be capable of excluding most of the silt and floating objects from accessing the irrigation infrastructure. In the case of Bura Irrigation Scheme, a submerged weir is provided at the diversion canal mouth to exclude heavy sediment. As the water flow into the 15m wide siltation basin the velocity decreases allowing for deposition of the suspended solids. The siltation basin will be desilted regularly to create room for the incoming silt.
style=”text-align: justify;”>At what point will Bura Irrigation Scheme farmers start using water from this infrastructure?
Korakora gravity intake is currently at 95 percent expected to be completed by end of this year, while the 26km canal is expected to be completed by the end of 2023. The gravity project will then be commissioned while Nanighi pumping station will be decommissioned. Irrigation water will be released to the scheme by gravity in accordance with the schemes water demand.
Which milestone will the Authority achieve in Bura Irrigation Scheme through this infrastructure?
This being a gravity-fed system, operating costs will go down because there will be no diesel pumps, which have expensive operating and maintenance costs. Additionally, this will increase the amount of abstracted water from the current 3m3/second to 11m3/second allowing increasing area under irrigation.
Is this one of your biggest implementing project?
It is. In fact, I express my heartfelt gratitude to the CEO for giving me the responsibility of managing the implementation of the project and to the three DGMs for their oversight and to my co-workers and the consultants for the immense effort they have put to make the project succeed.
Message to the farmers?
You have been waiting for a while, but I can promise you that the project is on track. After completion, the rate of water abstraction will rise to 11 cubic metres per second from the current three cubic metres per second. The successful implementation of this project will ensure reliable water supply improve agricultural productivity and help modernise and stabilise and lower cost of irrigation operations.
This will boost the food and nutrition security of farmers and other residents of Tana River County, enhance wealth creation and provide jobs by expanding the irrigated area from the present 10,000 to 25,000 acres. Additionally, it will make a significant contribution to the manufacturing sector through processing of irrigated industrial crops such as cotton and sunflower.
Message to the team behind the implementation of the project?
I appreciate the tremendous effort the team has put into implementing the project, especially since the construction of the intake, employed the unique technology of secant piling that is not frequently employed in this nation. Their capacity to overcome variety of challenges and quickly pick up new experiences has resulted in high-quality work and efficiency in project implementation.