ZRA warns ZESCO over excessive water use at Kariba dam

The Zambezi River Authority (ZRA) has raised alarm over Zambia's state power utility, ZESCO's excessive use of water at Kariba Dam, warning that continued overconsumption could deplete the reservoir's usable water and force a shutdown of electricity generation at the dam.

ZRA, a bi-national body jointly owned by the governments of Zimbabwe and Zambia, made the warning in its 2025 Hydrological Outlook and Water Utilisation Report, noting that ZESCO had already exceeded its annual water allocation and must scale back power generation immediately.

Kariba Dam supplies hydropower to both countries, with ZESCO operating the North Bank Power Station (1 080MW capacity) and ZESA Holdings managing the South Bank Station (1 050MW).

For 2025, ZRA allocated 27 billion cubic metres (BCM) of water between the two utilities — later increased by 1BCM to 28BCM — giving each country 14BCM.

However, as of October 15, 2025, ZESCO had already exhausted its allocation and had gone on to use 0,31BCM more, representing 2,2 percent over-utilisation, while Zimbabwe still had 3,63BCM in reserve.

ZRA warned that if Zambia's overuse continued unchecked, it could drain the dam's live storage, making it impossible for either country to continue generating hydropower.

"ZESCO Limited was in the process of implementing measures to scale down power generation at Kariba Dam to minimise the ongoing utilisation of water above allocation," said the ZRA report.
"If left unchecked, this could lead to the complete exhaustion of usable water at Kariba, resulting in the shutdown of both power stations."

Hydrological simulations earlier projected a closing storage of 4,4BCM for 2025, assuming both countries adhered to their allocations. However, ZESCO's excess drawdown means the actual figure will likely fall below this level.

Analysts note that Zimbabwe's adherence to its water allocation is largely due to major investments in alternative energy sources, including solar and thermal power, which have eased dependence on Kariba hydropower.

The country has seen significant growth in private-sector solar adoption, with industries and households installing on-site generation systems to cushion against load-shedding.

This strategy, experts say, has lessened pressure on the national grid and enabled the country to comply with ZRA's operational guidelines.

For 2026, ZRA has increased the overall water allocation to 30BCM, divided equally between Zimbabwe and Zambia. Each country will be allowed to use 15BCM, with power generation capped at 250MW per country during January and February 2026.

ZRA said it would review the cap in March 2026, with a possible increase to a combined 800MW generation limit, depending on inflows and lake levels.

The projections are based on a normal-to-below-normal rainfall outlook, with expected inflows of about 37,5BCM into the lake in 2026.

The Zambezi River Basin, which sustains Kariba, continues to face the escalating effects of climate change, including prolonged droughts and erratic rainfall patterns linked to the El Niño phenomenon.

These climatic shifts have reduced water inflows into the reservoir, posing long-term risks to energy generation and water security in both Zimbabwe and Zambia.