By Lerato Ndlovu
Victoria Falls and Chavuma stations recorded improved rainfall performance and water flow this year but with no significant rise to Kariba lake levels constraining electricity generation capacity.
Zambezi River Authority (ZRA) chief executive engineer, Munyaradzi Munodawafa, in a media briefing in Zambia issued hydrological updates on information received from 13 gauging stations.
The stations operated by the authority and located within the Kariba catchment area affect water levels for power generation at Kariba Station under the current 2019/2020 rainfall season.
“Since our last briefing, we continued to gather hydrological information to inform reservoir operations at Kariba as the rainfall season progressed.
“Our main focus is on two stations, namely Victoria Falls and Chavuma which are the key stations that indicate the performance of the mainstream Zambezi River, contributing over seventy five percent (75%) of inflows into Lake Kariba.
“The recorded flows at the two gauging stations are higher than the flows recorded during this period last year at the same stations, indicating an improvement in the rainfall performance and inflows recorded this year, but with no significant rise in the Kariba Lake levels therefore, generation capacity remains constrained,” he said.
He added that power generation at Kariba Dam relies on availability of adequate water which also depends on the rainfall received in any season.
“We were already informed by the local meteorological departments on the projected performance of the 2019/2020 rainfall season to the fact that normal to below normal rainfall was projected for the first quarter of 2020 forcing the Authority to take a precautionary approach in the water allocation for power generation at Kariba, allocating 22 Billion Cubic Meters of Water to be shared equally between the two power stations at Kariba spelling out a combined power generation level of an average 550MW at Kariba.”
Flows recorded at Chavuma indicated an increase of about 3159 m3/s between the 7th and 21st of February 2020, trending above the long term average by 208% when compared with the current flows recorded on 21st February 2020 of 4621m3/s higher than 2019 february 21st by 804%.
He stated that Barotse flood plains are filling up giving a significant of higher river flows from Chavuma.
“Given the four (4) weeks’ time lag in terms of the flows at Chavuma reaching Victoria Falls, as well as the influence by the Barotse flood plains located between the two stations, which if dry has a tendency to retain inflows received from Chavuma.
“Our hydrological simulations indicate that we could by end of March 2020 begin to notice some marked influence of the higher river flows from Chavuma at Victoria Falls.
“The Barotse flood plains which are estimated to take up a water storage of about 8.6 billion cubic metres at normal flood levels, is now filling up; confirming the increased runoff and river flows from the Zambezi headwaters monitored at Chavuma Station.”
Flows Recorded at Victoria Falls, are averaging around 831 m3/s which is a twenty five percent (25%) improvement from the 663 m3/s flowrate recorded on 7th February 2020, though they are still thirty four percent (34%) lower than the recorded long-term average lake inflow of 1254 m3/s.
Kariba lake level rose by 30cm between 7th and 21st February 2020 recording an increase in flows as a result of the improved rainfall and inflow from both the upper and lower Kariba catchment during the stated period.
On 21st February 2020, according to the statement read to media, the recorded lake level at Lake Kariba was 477.01m, with 10.4% or 6.7 Billion Cubic Meters (BCM) of usable storage, which is lower by 76% than last years recorded volume with simulations that the lake level will reach a peak in June 2020.