Flooding in Ghana's Volta Region: An Analysis Using GIS
by Sylvanus Narh Duamor
Sylvanus Narh Duamor is a first-year Master of City Planning student in the Land Use and Environmental Planning concentration. Sylvanus is passionate about promoting land use and environmental planning through research and practice, with a special focus on advancing environmental sustainability through climate adaptation and resilience and energy policy. He aims to provide constructive contributions to local, regional and international development planning efforts.
On September 15, 2023, the Volta River Authority (VRA) began a controlled release of water from the Akosombo Dam to prevent it from potentially overtopping. The spillage led to flooding in low-lying areas along the river, including Mepe, Battor, Sogakope, Mafi, Adidome, Ada, and other communities. About 35,900 residents were displaced as a result of the flooding, according to UN, Ghana [1]. Using GIS, I try to understand how and why the flooding occurred in those areas
The Akosombo Dam is one of the largest hydroelectric dams in Africa. It was constructed to generate electricity for the whole of Ghana and its eastern neighbors, including Togo and Benin. Since the time of the dam’s construction, the VRA has been forced to conduct several spillages to safeguard the dam’s integrity and prevent devastating consequences–the most recent spillage occurring in 2010 [2]. The impact of the flooding incident that occurred in 2023 was particularly alarming. In addition to being displaced, many of those affected also lost their possessions and livelihoods, as the water inundated their homes and farms. Furthermore, important infrastructure such as roads, bridges, and schools were damaged. The impacts also extended to biodiversity and ecosystems in areas both upstream and downstream of the dam.
Reports indicate that the impacts of the spillages carried out by the VRA have only been increasing–the impacts of each spillage being more severe than the ones before. There are a few factors that have contributed to this. Statistics show that there has been a surge in the total annual rainfall over the past few decades [3]. This implies that more water will be drained into the Volta Lake each year until a change in rainfall pattern occurs. A further implication is that the spillages will become more frequent in the coming years. Also, the amount of water that is spilled may depend on the spillage of the Bagre Dam in Burkina Faso (which also has severe impacts on communities in the northern part of Ghana). Another factor that has contributed to the increasing degree of the impacts of the spillages is increasing population in communities downstream and the accompanying settlement expansion along the river. As more people settle in these communities, more people become vulnerable to flooding and are consequently affected by it. The trends of increasing annual rainfall and increasing vulnerable population form a grave combination.
The public and other critics have blamed the VRA for flooding the communities downstream. The VRA, on the other hand, absolves itself from the allegation, indicating that it was a necessary action to prevent a more devastating impact that would be felt not only by the communities downstream, but also by the entire country [4]. Many have argued that the VRA could have been more proactive in providing timely information about potential spillages. Others also argue that there has been inadequate monitoring and evaluation of past and current trends of water accumulation at the dam, and no plan for mitigation. The question of how to address the increasing population in communities downstream is another critical matter. These are very important contentions that the VRA, NADMO, the government, and other agencies must grapple with. My aim in this study was to understand how and why communities such as Mepe and Battor experienced the greatest impact during the most recent flooding incident through GIS.
I began by delineating Ghana’s watersheds using Arc Hydro in ArcGIS Pro using Digital Elevation Model (DEM) data on Africa gathered from the USGS website [5]. The watershed analysis revealed that there are 81 streams/rivers in Ghana. However, these account for only major rivers and streams. There were other smaller streams that drain into the ones mapped here.
The results showed that almost all the streams and rivers north of the Akwapim-Togo Ranges drain into the Volta River, and the outlet of all the water upstream was the Akosombo Dam. The lake formed as a result of the dam is considered the largest artificial reservoir in the world based on surface area.
The VRA spilled water at a rate of 183,000 cubic feet per second. Reports indicated that low-lying areas along the river, including Mepe, Battor, Sogakope, Mafi, Adidome, and Ada were flooded due to the dam spillage, and satellite images show that these areas are essentially located in wetlands, which are prone to flooding. By mapping the elevation of those areas, I found that they were only five meters above sea level and were also lower than all the areas through which the waters passed before reaching them, making them the most susceptible areas to the incoming spilled water. Battor and Mepe, being the first of the low-lying communities, were hit the hardest.
By using GIS to map the areas that were impacted by the spillage, we now have a better understanding of how and why the flooding occurred at Mepe, Battor, Sogakope, Mafi, Adidome, Ada, and other communities. Three main interconnected factors were identified: first, the Akosombo Dam is the faucet to the largest man-made water reservoir in the world (by area) and opening this faucet to release 183,000 cubic feet per second implied flooding downstream. Second, the areas that were impacted were areas that were low-lying. Third, the areas that experienced the greatest impact were low-lying areas situated along the river that were closest to the dam (since the water would accumulate in these areas first before spreading downstream). This explains why Mepe and Battor were impacted the most. From a planning perspective, this requires delicate planning measures that safeguard the lives and livelihoods of the people living in these areas while preserving these ecologically sensitive zones.
Image: Akosombo Dam spillage.
Source: Myrna Machuca-Sierra
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Image: Lake Volta watershed shown in Ghana, highlighting streams that act as drainage for the watershed.
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