New data show that the domestic electricity system is coming under strain as its two largest hydroelectric dams – the Bui Dam and Akosombo Dam – face simultaneous pressure, heightening risks of instability across the power system.

An analysis by the Institute for Energy Security (IES) – which tracked weekly average elevation levels at Bui from January 2022 to March 2026 – revealed a sustained decline in reservoir strength, with the dam transitioning from a stable seasonal system into what it describes as a “more volatile and constrained regime” between 2024 and 2026.

The report identified 2024 as the peak of hydrological stress, with 2025 marking a persistence phase – indicating what the Institute’s analysts described as a multi-year deficit cycle rather than a temporary fluctuation.

“The data identify 2024 as a stress peak and 2025 as a persistence phase, signalling a shift from a temporary variability to a multi-year hydrological deficit cycle,” IES said.

Over the four-year period, Bui’s reservoir followed a consistent seasonal pattern – peaking between August and October before declining steadily, with its lowest levels recorded between February and April.

However, recent years have shown deeper troughs and weaker recovery cycles, particularly in the first quarter – which has now emerged as the system’s most vulnerable period.

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The Institute noted: “The first quarter has become the defining vulnerability period, characterised by lower starting elevations, faster drawdowns and tightening operating margins across all recent years”.

This development comes as both Bui and Akosombo experience reduced inflows and increased demand pressures, limiting the ability of one dam to compensate for the other… a key stabilising feature in previous years.

“Moreover, the challenges observed at Bui are not occurring in isolation but are consistent with trends seen at other major hydro assets such as the Akosombo Dam,” a portion of the report read.

IES warned that the growing synchronisation of stress across Ghana’s hydro plants could significantly weaken supply reliability, especially during peak demand periods.

“The synchronisation of stress at Bui and Akosombo points to a system-wide hydro vulnerability, threatening Ghana’s power supply and its position as a regional energy exporter,” the report stated.

Historically, hydropower has provided a dependable base for Ghana’s electricity generation – supporting both domestic consumption and exports to neighbouring countries. However, the new findings suggest that this reliability is being eroded by a combination of operational pressures and changing climate conditions.

In recent years Bui has increasingly been deployed to support peak demand, particularly during the dry season. While this has helped stabilise the grid in the short-term, it has also accelerated water depletion and reduced the dam’s ability to respond in future demand spikes.

The situation is compounded by broader climatic shifts including shorter and less predictable rainy seasons as well as higher evaporation rates, all of which have contributed to reduced reservoir replenishment.

To manage the shortfall, operators have leaned more heavily on thermal generation – including plants run by Volta River Authority and independent power producers. However, this shift has implications for both cost and system efficiency.

The Institute warned that without a more coordinated and adaptive approach to hydro management, the country could face recurring supply constraints during critical periods.

It called for improved planning frameworks that recognise seasonal vulnerabilities – particularly in the first quarter – and emphasised the need for strategic water conservation to preserve minimum operating levels.

“Considering these dynamics, a comprehensive set of strategic interventions is required to safeguard energy security. Central to this is the introduction of a more sophisticated hydro dispatch optimisation framework that prioritises the preservation of minimum reservoir levels during critical periods,” IES said.

“Establishing clearly defined elevation thresholds below which generation is restricted would help prevent the system from entering dangerously low operating zones. At the same time, there is a strong case for accelerating the deployment of complementary renewable energy sources – particularly solar power, which naturally peaks during the dry season and can therefore offset reduced hydro output,” it continued.

As pressure builds across the system, IES described Ghana’s energy sector as entering “a period of transition”, where traditional assumptions about hydro reliability may no longer hold and where simultaneous stress across key assets could become a defining feature of the power sector.