Source: The live and dead waters of Lake Kariba | The Herald 14 AUG, 2019
A view of Kariba Dam whose water level has fallen drastically, affecting electricity generation Walter Nyamukondiwa Kariba Bureau
WELCOME to Kariba, a land of paradoxes, a place where dead water lives in perfect, almost indecipherable harmony with living water.Where water flows congenially along the mighty Zambezi River into Lake Kariba, one of the biggest, if not the largest inland man-made lake in the world.
Once in the lake, amongst the waters is the dead and living, the Zambian and Zimbabwean waters.
Confusing right!
It is indecipherable until you start experiencing up to 18 hours of load shedding and all its attendant challenges, including living in darkness and resorting to alternative fuel including firewood which takes people back to their roots.
Kumusha!
The dead water subsume its inherent qualities into the living waters to operationalise a pact where life will be sustained in abundance.
Perhaps, the peace and tranquillity is disturbed with the occasional revolt of the dead water in the form of waves that can be a nightmare for any sailor.
That’s only my imagination running wild.
However, the pact has sustained fish of all shapes and sizes, frogs even, with mammals including buffaloes, zebras, elephants and humans trooping to the lake to quench their thirst.
The pact has subsisted for the past 60 years when the Kariba Dam was completed and water started filling the lake.
At full capacity, it covers 282km in length and 32km across at widest point.
It is about 116 metres at the deepest point and covers an area of 5 180 square kilometres.
Dead and live water is the parlance of the learned, the language of those who went through the rigours of Mathematics and Physics in engineering school.
They combined their engineering ingenuity to create the dam wall, set up the hydroelectric power plant and maintained it for industrial and household electricity use.
Holding a massive 185 cubic kilometres of water at its fullest, about 65 cubic kilometres of it represents 35 percent of water which is regarded as live water for electricity generation purposes.
This is the so-called live water for engineers to work with. The remaining 65 percent, about 120 cubic kilometres is regarded as dead water.
This is where the paradox begins.
How can we be told that water levels in Lake Kariba are low when we see the water?
Of course the levels have gone down, but how does that affect generation and plunge the country into darkness?
How can Kariba Town go thirsty with an adjacent behemoth of a water body?
The hydro-electric power plant is within a 128 metre high concrete arch dam which is 633 metres along the crest.
Construction began in 1955 after the project was given the green light by the then Federal Government of Rhodesia and Nyasaland made up of Zambia, Zimbabwe and Malawi.
Designed by Frenchman Andre Coyne, the project’s main contractor was Impresit from Italy. The work of engineers from both sides of the Zambezi River — Zimbabwe and Zambia — under the auspices of the Zambezi River Authority (ZRA) is to maintain a delicate balance that will not lead to live water varnishing, therefore, leading to the shut down of the power station.
They do that in collaboration with engineers from the Zimbabwe Power Company and power utilities.
ZRA allocates water equally to the two countries, which is reviewed from time to time, depending on the availability of water.
ZRA chief executive officer Engineer Munyaradzi Munodawafa in a recent interview said allocation of water depends on ecological factors around the Zambezi Catchment.
“If we have good rains upstream of the Zambezi and its tributaries, then we start seeing water rising from May. If we have sufficient water that leads to water filling in the lake, which means it will be enough for power generation at full capacity for the Kariba South and North power stations.
“However, if water levels are too high to threaten the integrity of the dam wall, then we release water through the floodgates to manage water levels,” said Eng Munodawafa.
The prospects of the power stations shutting down look ever more real as live water, which is used for power generation has gone down to about 23 percent.
Trends show that live water is dying at a rate of about 1 percent every two weeks, with engineers from the Zimbabwe Power Company saying it will be ready for burial in October at the current rate.
To that end, power production has been scaled down from the installed generation capacity of 1 050MW after being upgraded from 750MW of power.
ZRA capped production for both Zimbabwe and Zambia at 358MW for the south and north power stations.
ZPC business development manager Engineer Bernard Chizengeya said Zimbabwe had diminished allocated water for generation at that level and had downgraded production to 227MW and currently 180MW.
At current levels, power produced is not enough to power Harare alone.
“We have already used up water for production levels of 358MW per day. We have used most of our water during winter where normally we maintain all units at running.
“From July, we were supposed to come down to 227MW from 358MW.
“However, in July, we were generating at an average of 408MW, instead of an average of 227.
“This means we doubled our consumption. So from Kariba Power Station, we are supposed to produce 180MW daily,” said Eng Chizengeya.
The precarious state of affairs means that Kariba Power Station could be decommissioned next month as water levels are fast dwindling unless solutions such as sustained imports to complement local generation are implemented.
Live water level is currently at 478 metres and power production will cease when it gets to 475m, which means we are left with only three metres of water.
Therein lies the conundrum.
At 475m, we would have reached the short horizontal intake which takes water through a radial gate and through a vertical penstock to the turbines.
This means that below the 475m level, dead water comes alive, but there is no mechanism for making it useful in terms of power generation.
It remains useful for recreational purposes including fishing and water sports and boating among others.
As the live water reaches its swansong, it bows down, ironically leaving the dead water to continue giving and sustaining life.
The death of the live water can be felt in lands far away where its exertions have helped to light up homes, fire industries and cooking of varied recipes to sate appetites.
It remains to be seen when the heavens will resurrect the dead water and put a smile on people who have had to endure long hours of load shedding.
Feedback: wnyamukondiwa@zimpapers.co.zw
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