By Akintola Omogbodun
The River Ogun system has the River Ogun and the River Ofiki starting in Oyo North. River Oyan has its origins in Oyo North and the north-western part of Ogun State. It is joined by the River Ofiki west of Igbo-Ora and it flows into the River Ogun north of Abeokuta.
There are a number of tributaries of the River Ogun such as River Ogbara, River Opeki, River Ose, River Oso and River Awon which join the River Ogun at various locations north of Abeokuta. River Onigbongbo and River Ewekoro are the major tributaries south of Abeokuta.
The major infrastructure of significant economic value within Ogun State and on the River Ogun system is the Oyan Dam. This dam, which was built by the Ogun-Oshun River Basin Development Authority, OORBDA, is located on the River Oyan 20km north west of Abeokuta.
Ogun State is not deriving optimum benefits from this dam and the lake created behind it. Rather, in recent years, water releases from the dam have been used to create destruction and disruption of livelihoods and economic life in communities downstream of the dam contrary to the operational principles adopted for the design and construction of the dam.
The primary economic benefit that can be derived from the dam and its lake is the generation of 9MW of hydropower. This benefit has hitherto been neglected by the Federal Government of Nigeria, FGN. The Ogun State Government OGSG should take this economic benefit by entering into a joint venture arrangement with the FGN and a hydropower operator for the installation, operation and maintenance of turbines to generate 9MW hydropower. The OGSG should dedicate the power produced to the Ogun State Water Corporation/Abeokuta Water Scheme. This would make the project readily feasible as loans can be obtained at lower interest rates for water supply projects.
The lake at Oyan Dam has a capacity of 270million cubic metres, cu.m., and 9MW power generation would require the release of about 2million cu.m. of water from the dam each day. 730 million cu.m. of water would have to be released from the lake in a year, about 2.7 times the lake capacity.
Records for the period 1992 to 2002 show that the maximum quantity of water released from the dam in one year was about 546.9 million cu.m. in 1992. 522.7 million cu.m. of water was released during the months of January through to July and 24.2 million cu.m. in December while there were no water releases in August, September, October and November. Average water release in January to July was 2.45 million cu.m. per day while the December daily average was 0.78 million cu.m.
The floods observed downstream of Oyan Dam in 2007, 2010 and 2011 took place during the months of August, September and October. It is evident that if power is being generated from Oyan Dam and 2 million cu.m. of water is being released from the dam everyday, there would be no floods in places like Abeokuta close to the dam and in places like Punchplace, Warewa, Riverview Estate, Opic Estate, Lonex Gardens, Riverbank Estate and Guinness Cooperative Estate which places are close to Lagos State and the Lagos Lagoon.
The list of major tributaries of the River Ogun has been provided above such that the OORBDA can identify the tributaries that are making significant contributions to the flow in the River Ogun and which tributaries the OORBDA believes should be controlled to prevent flooding in Abeokuta and in communities downstream of Abeokuta. Buffer dams on the River Ogun tributaries identified by OORBDA can be considered for flood control purposes.
However, it would appear that the operational aspect of the OORBDA that requires attention is the provision of power for the gates at Oyan Dam. The gates are currently being powered by diesel generators and the OORBDA should be prevailed upon to apply its funds such that the gates are powered everyday and as an interim measure, one million cu.m. of water should be released from Oyan Dam each day.
The National Emergency Management Agency had in late March 2013 organised a consultative workshop – the 2013 Flood Prevention, Mitigation, Preparedness and Responses. In line with the aims of this workshop, the OORBDA should make public the quantity of water currently available in the lake at Oyan Dam, their estimates of the quantity and timing of water inflow into this lake during 2013 and their estimates of the quantities and timing of water releases from the dam during 2013.
I have indicated on 27 February 2013 while writing on Climate, Climate Change, the Dry and Wet Seasons in West Africa that current rainfall levels are not higher than what has been observed at various times over the last 100 years. The designs for the dams on the River Ogun system were based on these higher rainfall figures.
I reiterate that if the operational principles used when the dams were designed and built are adopted today, there should be no floods in Abeokuta and in other communities on the River Ogun downstream of Abeokuta.
The secondary economic benefit would come to Ogun State when the OGSG is able to direct development in the flood-free estates close to Lagos State. These estates would serve as an anchor for an Ogun State Metropolitan Area stretching from Redemption Camp to Isheri North and on both sides of River Owuru as discussed in this column last week.