ADDIS ABABA — Ethiopia’s plan to build Africa’s biggest hydropower dam on the main tributary of the Nile River must address concerns that there may be flaws in the design of its foundations, a group of international experts says.

The experts also called for further studies on the effects of the 6,000MW, $4.7bn project on the downstream nations of Sudan and Egypt, the International Panel of Experts said in a report.

Egypt, which relies on the Nile for almost all of its water, expressed alarm about the dam when Ethiopia diverted the Blue Nile in May as part of the construction process.

"Structural measures might be needed to stabilise the foundation to achieve the required safety against sliding" of the main dam, according to the report.

There are also "weak zones" in the rock that will support an auxiliary dam that need to be studied, the panel said.

Construction of the Grand Ethiopian Renaissance Dam is part of a government plan to spend 569-billion birr ($30bn) on infrastructure in the five years until mid-2015. Ethiopia, Africa’s second-most populous nation, aims to become an industrialised middle-income nation by 2025.

Ethiopia is the source of 86% of the water that flows into the Nile, the world’s longest river that runs 6,656km through 11 countries from Burundi in the south to Egypt, where it empties into the Mediterranean Sea.

Ethiopia has said it will take five to six years to fill the 74-billion cubic metre reservoir created by the dam.

The panel, which held its first meeting in May last year, was formed at the suggestion of Ethiopia’s government. It comprised two specialists each from Ethiopia, Egypt and Sudan and four specialists from other nations.

The report, which has not been made public, was submitted to the three governments in June. It was e-mailed to Bloomberg and its authenticity verified by Ethiopia’s foreign ministry.

Ethiopia said the report found the project to be of international standard and would not cause "significant harm" to downstream countries. Egypt, however, said the report was inconclusive.

Ethiopia delivered a hydrological study to the panel that analysed the downstream effect of the reservoir-filling period given low, average or high rainfall.

The project document concluded Egypt faces a 6% reduction in the electricity-generating capacity of the High Aswan Dam and no water loss if the reservoir were to be filled during years of average or high rainfall.

If the reservoir were filled in a dry year, it would "significantly impact on water supply to Egypt and cause the loss of power generation at High Aswan Dam for extended periods", according to the document.

A "comprehensive" additional study of the dam’s effect on water resources should be conducted, the panel said after reviewing the document.

"The analysis presented is very basic, and not yet at a level of detail, sophistication and reliability that would befit a development of this magnitude, importance and with such regional impact," the panel said.

Ethiopia is working with Sudan and Egypt to enact the panel’s recommendations, said spokesman for the foreign ministry, Dina Mufti, in an interview yesterday in the capital, Addis Ababa.

Bloomberg