Zesco manager Monica Chisela said the gates of the dam, which is on the Kafue River and supplies power to key copper mines, were opened to avoid its collapse, but flooding was not yet threatening the Kafue Flats game park downstream. "It was assessed that flooding due to opening of the spillway gates ... has not reached further downstream of the Kafue Flats," she told Reuters.
Six people have been killed in floods in southern Zambia since last month.
A senior industry official told Reuters that the Kariba dam, the main power generation point for Zambia and Zimbabwe which also exports to Namibia and Botswana, would be opened on Monday.
In 2005, The Zambezi River Authority opened spillway gates at Kariba North Bank power station on the Zambezi River, causing severe flooding in eastern Zambia and parts of Mozambique.
Zambia, Mozambique, Zimbabwe and Malawi have been lashed by heavy rains for several weeks, causing swollen rivers to burst their banks and forcing thousands of villagers to flee flooded homes.
(Editing by Phumza Macanda and Andrew Dobbie)