4th July, 2011
In a bid to avert flooding in the state, the Lagos State Government has inspected the two dams that could trigger off massive flooding in flood-prone areas in the state. They are Oyan in Ogun State and Ikere Gorge in Oyo State.
As a result of heavy downpour last year, the Ogun-Osun River Basin Development Authority (O-ORBDA), released water from the Oyan Dam into the Ogun River, which made it to overflow its bank with the attendant consequence of several communities in Ikosi-Isheri and Agboyi-Ketu areas of Lagos State being sacked by flood.
Officials of the Lagos and Ogun state governments visited the two dams last week to monitor their water level in a bid to quickly alert residents abutting River Ogun to leave if water overflows the dams which may lead to the release of water from them.
The Permanent Secretary, Office of Drainage Services, Lagos State Ministry of the Environment, Mr. Muyideen Akinsanya, during the inspection, expressed confidence that flooding would be put under control to avert a recurrence of what inundated communities on the Ogun River banks last year, saying that he was convinced that there existed enough room to contain more storm water from expected rainfall by the dams.
Akinsanya said that the inspection tour was to see the level of water in the reservoirs to enable experts plan ahead in view of the expected high intensity of rainfall this year.
â€œWe have experienced intense rain in Lagos as predicted by NIMET. The trip was to see the effect of the rain on the river and possible overflow to Lagos,â€ he explained, adding that the Joint Committee of O-ORBDA and Lagos State Government were capable of continuous monitoring of the rise in level of the rivers and issue early warning statements to the public and advise concerned governments on steps to be taken to avoid casualties.
According to him, â€œOyan Dam currently has three metres buoyancy capacity and as such, there is no cause for alarm, at least for now,â€ while appealing to members of the public to adhere to warnings so as to avoid disasters.
According to the Executive Director, Engineering, O-ORBDA, Mr. Bayo Alayande, â€œOyan Dam was built to keep the flow of Oyan River, a tributary of Ogun River, in check. The damâ€™s reservoir has water storage capacity of 270 million cubic metres. It has a length of 27 kilometres and width, six kilometres, while the surface area is 40-kilometer square. The dam, if explored for electricity generation, can generate maximum capacity of 9,000 kilowatts.â€
Alayande noted that the Federal Government, as part of the concern to tackle flood, had procured four Flood Early Warning Systems.
â€œOut of the four, two of them are located in Alamutu, Ogun State and Eruwa, Oyo State. The Early Warning System, which components include rain gauge, radar for reading and solar panel, has a satellite linked to computers in the office to monitor level of water rise in the river. The nearest of the equipment to Lagos, which is in Alamutu, is expected to trigger alarm whenever the water level rises up to 3.4 metres,â€ he said.
Contrary to the belief that the dams cause flood, Alayande stated that they were primarily built for flood control, provision of water to water corporations and electricity generation, adding that during dry season, water was released to increase capacity for storage during rainy season.
â€œIf the excess water was not held in the damsâ€™ reservoirs, it would flow freely and have caused a lot of damage on its route to the downstream. The amount of water being released from the dam is insignificant compared to the volume held back in the reservoir,â€ he added.
At the Ikere Gorge Dam, the Project Manager, Mr. Babatunde Ojo, told the team that the dam, which has capacity for the storage 555 million cubic metres, had many purposes including power generation, water supply, flood control and tourism.
â€œThe dam is capable of generating 3,750 megawatts of electricity. Ikere Gorge Dam has un-gated design, we can do little to water releases but what we do is to carry out systematic release to downstream to create space to contain excess water during rainy season and there is a spill barrier over which the water flows at a particular level.
â€œThe present level of Ikere Gorge Dam is 262 million cubic metres, spillover takes place by the end of July but this largely depends on intensity and frequency of rain. When it gets to 266 metres, it spills over to Ogun River and then flows to Lagos. The reservoir was to ensure that water is available during dry season and to control excess during rainy season,â€ he stated.