The Zambezi River Authority (ZRA) reported that the lake level at Kariba Dam, which had been in recession in the last quarter of 2022, has been rising steadily after the onset of rains on and around the lake and Zambezi River Upper Catchment.
Kariba Dam is 128 m tall and 579 m long. The dam impounds water for the 1,830 MW Kariba hydroelectric plant. It consists of the Kariba North Power Station operated by ZESCO Limited and the Kariba South Power Station operated by the Zimbabwe Power Company (ZPC).
The lake began 2023 with a low level of 475.61 m or 0.83% of live storage available for power generation. This level increased to 476.85 m recorded on Feb. 16, which translates to 6 billion cubic meters (BCM) or 9.32% of stored usable water meant for power generation by the two utilities. This level places the lake at 1.35 m above the minimum operating level (MOL) of 475.50 m.
According to the Africa Rainfall Climatology Rainfall Estimator of the U.S. Climate Prediction Center (CPC), the Kariba catchment can be said to have received normal rainfall over most parts of the upper catchment and normal to below normal over the larger part of the lower catchment during the last 90 days of the 2022/23 rainfall season (November 2022 to February 2023).
This outcome is in sync with the seasonal rainfall outlook prediction — by the CPC and the SADC Climate Services Centre’s 26th Southern Africa Regional Outlook Forum and the downscaled forecasts of the Meteorological Departments of Zambia and Zimbabwe — of normal to above normal rainfall over Southern Africa in general and the Kariba catchment in particular. This situation has resulted in generally average inflows into Lake Kariba that, coupled with the controlled power generation outflows, has been responsible for the increasing water levels at Kariba Dam.
A significant increase in the Kariba Dam water level will only start being recorded between April to June 2023, which is the period during which the waters from the Barotse Floodplains greatly influence water levels at Lake Kariba, according to the authority. Due to this, water allocation to the two power utilities will not be increased in the short term.
Both utilities have adhered to the authority’s guidance by capping average generation at each power station at 250 MW in December 2022 and recently capped at 350 MW. This generation output will be maintained while the hydrological outlook continues to be reviewed during the weekly Joint Technical Committee (JTC) meetings between ZRA and the two Kariba power generation utilities.
ZRA allocated 40 BCM of water to cater for power generation operations at Kariba for 2023. This allocation is being shared equally between ZESCO and ZPC for their respective power generation operations. The authority will continue to monitor the hydrological outlook in the Kariba catchment and, where necessary, adjust this water allocation in an effort to sustain reservoir operations at Kariba.
ZRA is a bi-national organization mandated to contribute to the economic, industrial and social development of the Republics of Zambia and Zimbabwe by obtaining the greatest possible benefits from the natural advantages offered by the waters of the Zambezi River through the most economical and effective means of providing water for generation of electricity and for other purposes the contracting states may decide upon.
