From the Wiki article-
On 3 October 2014 the BBC reported that “The Kariba Dam is in a
dangerous state. Opened in 1959, it was built on a seemingly solid bed
of basalt. But, in the past 50 years, the torrents from the spillway
have eroded that bedrock, carving a vast crater that has undercut the
dam's foundations. … engineers are now warning that without urgent
repairs, the whole dam will collapse. If that happened, a tsunami-like
wall of water would rip through the Zambezi valley, reaching the
Mozambique border within eight hours. The torrent would overwhelm
Mozambique's Cahora Bassa Dam
and knock out 40% of southern Africa's hydroelectric capacity. Along
with the devastation of wildlife in the valley, the Zambezi River
Authority estimates that the lives of 3.5 million people are at risk.”[22]
That reminds of that old joke I've heard that starts out-
"What did people in Rhodesia use before they had candles?"
The answer being,of course,
"Electricity!"