VRA must do more to avert future Lower Volta flood damage
With high inflows into the Volta Lake, the Volta River Authority (VRA) triggered its Emergency Preparedness Plan and Standard Operating Procedures, including commencement of controlled spilling of excess water from the Akosombo Dam.
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The large volume of excess water released (VRA mentions some 183,000 cubic feet per second) has caused unprecedented flooding of many communities, causing extensive damage to homes and assets and investments, according to news reports.
The flooding is because VRA has had to open the spillways of the Akosombo Dam to let out, quickly, excess water raising the water levels in the Volta Lake behind the dam, as critical to the safety of the Akosombo Dam, by never allowing the water level in the Volta Lake to go above the designed maximum lake level of 278.0 feet.
The most important objective of the VRA is to effectively harness the water resources of the Volta River to generate the maximum potential power possible for Ghana.
For the purpose of this piece, the effective management of the water resources of the Akosombo Dam requires the VRA to do three interrelated activities:
Managing
Managing levels of water in the Volta Lake. The VRA has done a fairly good job managing the water level in the Volta Lake.
From literature, the maximum lake water level ever recorded was 277.54 feet on November 8, 2010 (source VRA). It has never gone above the maximum operating water level of 278 feet.
VRA has however recorded periods when the lake water level had fallen below the minimum operating lake level of 240 feet.
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On July 21, 2007, it was 234.96 feet (source VRA), albeit as a result of prolonged drought periods.
The VRA, therefore, manages this activity very well.
Monitoring
Monitoring volume of inflows into the Volta Lake: The VRA, as one of the high-performing public institutions in Ghana, must have in place a comprehensive Reservoir Simulation and Management model.
Such a system should ideally allow sufficient time to predict changes to lake water level at the dam site.
I was, therefore, surprised to read news reports recently of VRA conceding a lack of capacity to predict when the current spilling exercise would be ended.
In the news item, a top official of the VRA is quoted as saying, "We can't tell specifically.
We wish this will stop within about a week, but this may continue even though we are anticipating that the levels may drop … " Akosombo Dam spillage: VRA unsure when exercise will end, (October 13, 2023.
This is difficult to accept from the VRA.
Regulating
Regulating volumes of outflows from the Akosombo Dam: The VRA, based on its main objective of optimum generation of power, would definitely aim to ensure that it releases just the right quantity of excess water and to close spillway gates at the right time to ensure that lake water levels remained very close to the maximum water level.
Any spillage, which results in a rather larger than necessary drop in lake water level, otherwise is a failure as it ultimately affects the maximum potential power that can be generated going forward. How well is VRA walking this thin line?
This year, it appears responding to the rising lake water level and opening the spillway gates on September 15, 2023 was inadequate and too late!
As at Friday, October 13, 2023, four of the 12 spillway gates had been fully opened after the initial phase one opening, creating a spectacular thundering sight, which unfortunately is wreaking havoc downstream!
The immediate danger is the indication from VRA that current inflows are in excess of 400,000 cubic feet per second, whilst outflow is in the region of 183,000 cubic feet per second.
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My prayer is for the reservoir to be able to contain the surcharge, from the net inflow of some 200,000 cubic feet per second plus and remain under the critical 278 feet level.
Going forward, how do we spill excess water from the Akosombo Dam in smaller volumes over longer periods of time to save life and property in the regions downstream of the dams?
This is the challenge facing the VRA now! Thankfully, the VRA should have the resource to solve this problem!
The writer is a Civil/Irrigation Engineer