Cape Verde is facing its worst drought since 1977, local media reported.
The state-owned Rádio de Cabo Verde quoted Agriculture minister Gilbeto Silva saying the Poilão, the country's largest dam, had dried up.
The Poilão dam on the Santiago Island, was only two years ago overflowing.
“This is one of the worst droughts in the last 40 years,” Mr Silva said, adding the situation was only comparable to those experienced in 1977 and 1947.
The UN Food and Agriculture Organisation has included Cape Verde among the countries needing foreign food assistance, but Prime Minister Ulisses Correia e Silva, was quoted saying the situation was not about food insecurity.
“There is no problem of food insecurity for the Cape Verdean people,” the PM said.
Cape Verde is a volcanic archipelago off the western coast of Africa. It comprises 10 islands, opposite Senegal and Mali.
Nine of the islands are inhabited.
Cape Verde has few natural resources and suffers from scarce rainfall and limited fresh water.
Its population is estimated at 508,000 with a life expectancy of 74 years, one of the highest in Africa.
The country gained independence from Portugal in 1975 and is among the most politically stable states in Africa.
Cape Verde has experienced extensive emigration and it diaspora outnumbers the resident population. Virtually every Cape Verdean family has emigrant members.
Large-scale emigration started in the 1800s, when Cape Verdeans took part in a great trans-Atlantic migration, motivated by recurrent episodes of drought and famine.
The US, Europe, West Africa and South America host a huge number of Cape Verde diaspora.