Ethiopia continues to violate the international law governing transboundary rivers with its erratic operation of the Grand Ethiopian Renaissance Dam (GERD), disrupting the hydrological balance of the River Nile in both Egypt and Sudan.
Sudan has recently experienced flooding that submerged agricultural land across several states, causing extensive damage to property. The excess water also placed pressure on Egypt’s water management system, reaching the Aswan High Dam and forcing the Ministry of Water Resources and Irrigation to release additional volumes into the Nile.
This led to a rise in the river’s level, inundating low-lying floodplains.
According to Minister of Water Resources and Irrigation Hani Sewilam, Ethiopia’s unilateral operation of the dam has created alternating conditions of drought and flooding in Egypt and Sudan.
At the end of August and before the dam’s official inauguration on 9 September, Ethiopia reduced Nile water discharges to their lowest level of around 111 million cubic metres per day before abruptly increasing the outflow to 750 million cubic metres per day within a few days.
The sudden surge triggered the flooding witnessed in Sudan and placed further strain on Egypt’s water system. Egypt was able to contain the impact with the least possible losses.
The rise in River Nile water levels has caused damage to low-lying areas formed by the accumulation of Nile silt and considered part of the river’s natural course. The cabinet announced that this land may be at risk of flooding across 15 governorates in the Nile Valley and Delta.
The Menoufiya governorate recorded the highest level of damage, with approximately 1,241 feddans submerged by water. The Beheira governorate took proactive measures in coordination with the relevant authorities, chief among them the Ministry of Water Resources and Irrigation, by lowering water levels in the Rosetta Branch of the Nile.
As a result, only 61 feddans were affected in the governorate, all located in Kom Hamada.
There has been debate about how to manage the elevated water levels in the Aswan High Dam caused by Ethiopia’s unilateral operation of the GERD.
The first scenario is Egypt’s raising the storage level in Lake Nasser, the massive reservoir created by the construction of the Aswan High Dam, to its maximum capacity of 162 billion cubic metres. The second is opening the Toshka spillway, a man-made channel connected to Lake Nasser designed to divert surplus water into the Toshka Depression, a vast desert basin in southern Egypt.
The third scenario would be to increase the discharge through the Rosetta and Damietta Branches of the Nile to pass the excess water.
International water management expert Alaa Al-Sadek told Al-Ahram Weekly that there were several engineering, economic, and environmental considerations in this regard. He said that Lake Nasser at 182 metres above sea level can contain 162 billion cubic metres of water, while at a lower level of 178 metres it can contain 140 to 141 billion cubic metres.
The difference of approximately 21 billion cubic metres is the volume under technical consideration — whether to retain the water in Lake Nasser or release it through the Toshka or Nile outfalls.
Opening the Toshka spillway would discharge excess water into the depressions of the Western Desert. While this option would quickly relieve the pressure on Lake Nasser, it also diverts water into surface basins that will be wasted through evaporation and seepage, Al-Sadek said.
The Toshka spillway is a security measure to prevent a dangerous rise in water levels in Lake Nasser, not an economic option. Some of the released water might be used in future agricultural projects, but a large portion would be wasted, he said.
A proposed alternative is to direct excess water through the Rosetta and Damietta branches of the Nile towards the Mediterranean Sea during the period of peak flow, which is about 20 days or the time it takes the water to travel from Sudan’s headwaters to the Nile Delta in Egypt, Al-Sadek stated.
The exact duration depends on the hydrological characteristics of the flood and the speed of the flow.
Diverting the excess water through the Rosetta and Damietta branches of the Nile would allow it to reach the sea more rapidly instead of being stored in the Toshka Lakes, making it a less wasteful route since the water would remain within the Nile’s natural course.
However, Al-Sadek noted that this measure is also laden with risks. It may raise water levels in canals and irrigation networks across the Delta, causing the temporary flooding of farmland and residential areas if not carefully managed.
It could also disturb the ecological balance at the Nile’s estuaries and the Mediterranean coast by altering salinity levels and affecting fisheries and fishing practices. From a strategic standpoint, releasing water into the sea represents a permanent loss to the Nile Basin, as the water exits the system entirely.
Ensuring the High Dam’s structural safety and maintaining optimal operational levels requires a balance between maximising benefits and ensuring safe management, Al-Sadek said. The Toshka Lakes should be developed from an emergency measure to a productive option by connecting them to irrigation networks, energy sources, and infrastructure that would allow the use of the released water before it is lost through evaporation.
Al-Sadek proposed several engineering alternatives to address potential flooding scenarios in the event that Ethiopia continues its unilateral management of the GERD. He recommended running two-dimensional or standard simulation models to assess the impacts of different filling and discharge scenarios, including the opening of the Toshka spillway and discharges through the Rosetta and Damietta branches of the Nile.
He suggested adopting a dynamic operational policy for Lake Nasser that takes into account rainfall forecasts, early warning data from Sudan, and the need to maintain an emergency reserve for drought years.
If policymakers decide to use the Toshka spillway in part, a technical plan should be established to reuse the Toshka water effectively through pumping stations, canals, suitable agricultural projects, and treatment systems to preserve water quality, he added.
Al-Sadek stressed the need to enhance regional coordination through operational cooperation and real-time data-exchange with the Nile Basin countries, particularly Sudan, to mitigate possible floods before they reach Egypt.
To reduce water losses, he recommended strengthening medium-scale infrastructure by improving groundwater recharge networks and developing surface reservoirs.
* A version of this article appears in print in the 9 October, 2025 edition of Al-Ahram Weekly
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