Zambia has had some problems with the electricity supply recently. Why?
Hydropower is a natural source of energy, clean and dependable, and very suited and able to provide continuous supply 24 hours a day provided that there is sufficient water available. For professionals in the industry, this is known as “base load”. Alternative energy sources such as solar and wind have an inherent problem which is inconsistent supply, often failing when it is most required such as at night when the Sun is not shining or the wind is not blowing.
The other options, such as coal and gas are environmental polluters of note, and with global warming, are becoming a serious threat to our future, they deserve to be examined with great scrutiny to ensure the costs of the environmental damage they cause is realistically assessed. Zambia is blessed with rich natural resources, of which massive amounts of water is a major one. How can we effectively harness these advantages?
Most of our power comes from hydroelectric generating facilities, which were built before Independence or in the years immediately after. Has anyone given serious thought to how the rising demand for power in Zambia will be met by future generations? Or will our children be doing their homework by candle light?
Zambian electricity supply is heavily dependent on hydro, and this is because it is such an abundant and versatile source. But to ensure it will be used most effectively in the future, we need to critically examine how we are using it now, and what we can do to maximize its positive aspects in the future.
Kariba is a good starting point.
For more than fifty years, these installations have served Zambians well. So much so, that we have become complacent and over reliant on these facilities to the extent we have taken them for granted – until load shedding arrived!…. Now, with a situation that is a serious impediment to our economic development, loss of revenue to the main power provider, and a huge extra cost to businesses that have to purchase and run expensive generators, people have suddenly woken up to the fact that economic progress is intrinsically linked to power supplies.
What can be done?
Currently those responsible are regurgitating old solutions that were proposed over forty years ago. Kafue Gorge Lower was even commissioned in 2011 and then cancelled. Batoka Gorge has been the focus of numerous investigations since 1972, and now suddenly become urgent. The current deficit of electricity has been blamed on climate conditions, specifically the droughts of dry years. Rather than being a problem caused by Nature, this looks more like a problem caused by those responsible taking their eye off the ball!
As we have taken Kariba as an example, let us look at other possibilities in more detail that may have some merit. The water that drives the turbines at Kariba comes to that point as a result of rainfall. Where does that rain actually fall? Below is a map of the catchment area that supplies Kariba with its water.
The area outlined in green are the parts of Zambia and Angola that contribute to the total water flow received and used to generate power. Note that the central part of Zambia is the Kafue river catchment area, and does not flow into Lake Kariba! The Kafue River does join up with the Zambezi River, but that junction is much further downstream past Chirundu and so contributes no water to Kariba.
So, if the limiting factor to the amount of electricity it is possible to generate at Kariba is the amount of water received by rainfall in the catchment area, is it possible to increase this amount by our intervention? Obviously, it will have to come from some other catchment area. This is not as unrealistic as it seems at first glance. In the US about 90% of the water used in California comes from water diverted from other catchment areas! Water diversion is a very common way of taking water from where it is in surplus to areas where it is in deficit.
So where to look for more water?
Here is a huge catchment area that contributes no water to the Kariba dam. Can it be utilized? This is the catchment of the Kafue River. It is used to generate power at the Kafue Gorge hydropower facility, but is it using it all? Is it using it efficiently? When there is too much, what happens to the excess amount? Can the surplus be used in a cost effective way somewhere else?
Let us look at this more closely. What will determine if this is possible? Firstly, water does not run uphill! To be possible, Kariba must be much lower than the Kafue River. Is it?
The level of Lake Kariba at full supply is about 1700 feet above mean sea level. The level of the Kafue River at the point where it is possible to divert it is 3000 feet above mean sea level – more than enough to ensure a good flow of water!
Secondly, is the geography suitable for the construction of a canal to divert the water? How much will it cost to construct? A cursory glance at the topography of the area shows it is eminently possible and very feasible.
So what advantages will such a scheme bring?
As the infrastructure to generate hydropower is already constructed and installed at Kariba, it will be able to use this capacity without installing additional generating capacity. This includes the “peaking turbines” that have recently been commissioned.
It would also create the capacity to use the diversion canal for irrigation purposes
What about Kafue Lower Gorge?
Obviously, this would divert water from the generating capacity of this power station. Does this affect it? An unanswered question!
Can the experts please advise us on the practicalities of this alternative?
By Adrian Piers