By Dr Michelina Andreucci
THE operation of a hydro-electric scheme relies entirely on the energy produced by the force of falling water to provide the driving power through three main parts; intake and penstock, turbine, draft tube and surge chamber.
The generation of electricity is maintained by regulating the flow of water through the turbines and over the spillway, a formula known as the ‘rule curve’ which also determines the water level.
Electricity is mechanically generated by drawing water from Lake Kariba through a short horizontal intake via a radial gate and through a vertical penstock to the turbine spiral casing.
After passing through the turbine and producing power in the coupled generator, water at reduced pressure is passed through a suction cone and draft tube to the tailrace.
The water is then finally discharged downstream of the dam, back into the Zambezi River via three tailraces, each serving two machines.
Electricity was not part of the everyday life of many people, even in the industrialised Western world in the 19th and early 20th Century. As the public’s knowledge of electricity grew, however, electricity turned from a ‘scientific curiosity’ into an essential means for modern life, thus becoming a dynamic force for the continuing industrial revolutions and eventually for everyday domestic use.
Electricity is not to be looked at as a phenomenon or a cash cow (which it has been so far for ZESA). It has been part of daily lives since Edison flew his kite into the air and ‘discovered’ electricity for the first time; electricity has become a foregone basic right and a vital part of human survival and progress.
Kariba Dam has been a major driver of regional growth and development, contributing to regional economy and the surrounding areas, supporting fisheries, tourism operations, irrigation for agriculture and drinking water for local towns and villages. Notwithstanding that three-quarters of the population in the rural areas are still without electricity.
Since its origin, electrical power (electricity) has become an expedient way to convey energy and has been adapted to an ever-increasing number of uses; it is the lifeblood for industry, health, telecommunications, heating, security, lighting, cooking and refrigeration.
Commissioning the Kariba Hydro-Electric Power scheme in 1960, Queen Elizabeth, the Queen Mother, observed: “… the plant would generate power for the rapidly growing industries for this potentially enormously rich territory”; referring of course, to the Federation of Rhodesia and Nyasaland; now independent Zambia, Zimbabwe and Malawi, which today form part of the SADC membership group.
Twenty-nine (29) years later, by 1986, Zimbabwe was gaining self-sufficiency in electricity.
While the Victoria Falls Power Station is the oldest hydro-power station in Zambia, Kariba Dam provided more than 50 percent of Zambia and Zimbabwe’s electricity, benefitting an estimated 4,5 million people. Today there are an estimated 14 million people in Zimbabwe alone. Demand has obviously outstripped supply capacity.
To help meet the ever-growing demand for energy by SADC member-states, a number of hydro-generation projects in the Zambezi Basin have been proposed through the Southern African Power Pool (SAPP), with a potential capacity of over
20 000MW. The Zambezi Basin is considered to have enormous capacity for the region’s power supplies if well harnessed, since only 23 percent is currently being exploited.
Although these proposed developments have critical roles for the realisation of socio-economic development, not only for Zimbabwe but for the Southern African region, the damage on the eco-system which includes medicinal plants, animals, forage, honey, fruits, nuts, seeds, berries, mushrooms, oils, peat, insects and many others, will be considerable; not to mention the displacement and relocation of more people.
The Kariba inundation flooded 5 580 square kilometres of the Gwembe Valley; displaced over
57 000 BaTonga inhabitants who are still marginalised; wiped out all but a small portion of the animals — saved through Operation Noah and drowned all plant life.
Lake Kariba represents the exemplification of the unknown stress on the environment; destroying more habitat than any single human action had ever done before.
Through conservation, like-minded whites introduced their hydrological customs in a country without shoreline. They found the lake to be beautiful and turned Kariba from a wasteland, to one of the most scenic wilderness in southern Africa. Their Euro-Zimbabwean legacy, however, has benefitted a disproportionately few indigenous people.
While Zimbabwe and Angola may be the only two countries not signatories to the Ramsar Convention, they are none-the-less aware of the importance of ecological conservation, especially of wetlands.
In 1954, the government of Egypt decided to build the Aswan High Dam, resulting in the inundation of a valley containing the ancient Abu Simbel temples and other Egyptian treasures.
Through an initiative undertaken by UNESCO, the Abu Simbel and Philae Temples were taken apart piece by piece, moved to a higher location, and put back together.
The success of the project led to other conservation campaigns motivating UNESCO to initiate, with the International Council on Monuments and Sites, a draft convention to protect the common cultural heritage of humanity.
The salvage of the Abu Simbel temples in 1968 was undertaken by Impregilo, the Italian construction company founded in 1959. The present company resulted from mergers in 1990, including Impresit and Lodigiani SpA. Engineer Lodigiani was the head of Impresit during building of Kariba Dam Wall.
Other major works include buildings, public utilities, motorways, airports, water supply systems, waste disposals, hospitals and land development.
Projects they have carried out include:
1959: the Kariba Dam, Zimbabwe/Zambia,
1963: Dez Dam, Iran,
1966: Akosombo Dam, Ghana,
1968: Salvage of the Abu Simbel temples, Egypt,
1976: Tarbela Dam, Pakistan,
1998: Lesotho Highlands Water Project,
2002: Ecorodovias motorway system, Brazil,
2002: Ghazi Barotha Dam, Pakistan,
2003: Nathpa Jhakri Hydroelectric Power Project, India,
2005: Desalination plant Jebel Ali l1, United Arab Emirates,
2008: Kárahnjúkar Hydropower Project, Iceland,
2009: Milan-Turin and Bologna-Florence high speed railways, Italy,
Kariba is the result of centuries of Italian expertise. From as early as the Middle Ages, the Romans specialised in bridges, roads, aquifers, triumphal arches and commemorative columns. They built their arenas, colosseums and theatres using the mountain of stones in their environment.
The Romans’ discovery of concrete helped immensely in erecting their large and fortified edifices. They made concrete from a combination of sand and gravel mixed with water and some yielding cementing material, which usually consisted of a range of limestone, found in their areas.
The Romans also understood the use of pozzuolana – the volcanic sand found in the neighbourhood of Naples, which is still used currently to produce hydraulic cement in conjunction with lime.
Concrete is used for hundreds of purposes – for the foundations of buildings, pavements, dam walls, water tanks and all sorts of constructions which bear heavy burdens and are constantly exposed to violence of the elements; without which our modern civilisation would be unachievable today.
It has been said nothing short of dynamite is able to move it once concrete has set.
To date, the Roman Colosseum which was completed by Emperor Titus in the year 80AD and has been systematically plundered for over 1 000 years, still stands and makes a very imposing impression!
Patson Mbiriri, the Secretary for Energy and Power Development in the Zimbabwe Government is quoted as saying: “…We did not invest in the energy sector and the power sector for many years; hence the problem goes back to lack of investments in electricity infrastructure…”
Could this be where the problem lies?!
Dr Michelina Rudo Andreucci is a Zimbabwean-Italian Researcher, Industrial Design Consultant and Specialist Interior Decorator. She is a published author in her field. For comments E-mail:email@example.com