Wednesday, October 20, 2021

It is impossible to build any more dams in Botswana

Right hand throttling a sellotaped microphone, vibes of a friendly freedom-square crowd pulsating all around and – in the extremely rare case, the active ingredient of an exceptionally potent narcotic polka-dancing through the veins, it has become all too easy for some opposition politicians to propose a durable solution to Botswana’s water problems with a three-word slogan: “build more dams.”

It turns out though that those who toss off this proposal need to themselves build the most basic civil engineering knowledge about dams. If they do, they will most likely reach the same conclusion as those who occupy the commanding heights of engineering science: it is impossible to build any more dams in Botswana.

During odd intervals of the rainy season when God has forgiven forgivable sins and pressed the release button (like last month), rivers across Botswana have swelled and roared mightily. What most people are unhappy about is that more than 80 percent of the water goes to South Africa and going back to the days of Dr. Kenneth Koma, the founder of the Botswana National Front, there have been calls from the opposition for these rivers to be tamed and harnessed. And indeed that makes perfect sense because Botswana is a water-stressed country where in recent times, villages go without water for days on end. What Koma said has also found favour in the ruling party because when she contributed to the budgetary proposal by the Ministry of Minerals, Energy and Water Resources, Mahalapye East MP, Botlogile Tshireletso, suggested that the government should harvest water from the Mahalapye River. Tshireletso’s belief is similar to that once held by former vice president and Mmadinare MP, Ponatshego Kedikilwe in his brief backbench spell. Through a parliamentary question, Kedikilwe asked then why water was not being harvested from Segoditshane River in Gaborone. 

However, harvesting water that way will not be possible because according to the Minister of Minerals, Energy and Water Resources, Kitso Mokaila, a study that was carried out showed that Dikgathong Dam near Mmadinare was the last remaining dam site in the country. 

“It is the biggest dam and the biggest evaporating pan we have in the country because it has one of the longest dam walls. It is not a deep dam; it is a very wide dam and therefore it does not hold water too long because of evaporation. Your dam site ideally should be deep with very little surface area to reduce your evaporation ÔÇô just like Nnywane Dam. We had hoped we could find another dam site but all indications are that we have exhausted all the dam sites,” said the minister referring to a dam near Lobatse.  

What the minister said is confirmed by Meshack Balebetse whose company, Golden Ace, provides water and environmental engineering consultancy services. Balebetse knows an awful lot about water management having worked at the Water Utilities Corporation for 22 years. At the time he left the Corporation, he had risen to the position of Regional Director of Operations and Maintenance, responsible for water and wastewater infrastructure and systems. Previously he worked as Water Quality Manager responsible for national water quality management and compliance, optimisation of water and wastewater treatment processes, quality assurance systems, enterprise-wide risk management as well as safety, health and environment programmes. While at WUC, Balebetse also coordinated the commissioning of numerous water supply infrastructure development projects in the major urban centres and was a resource person for the planning and designing of major water treatment plants and reticulations.
 
Balebetse says that desperate as Botswana’s water situation may currently be, constructing dams to extract water from Mahalapye and Segoditshane Rivers would have serious repercussions (damage to property and loss of life) that far outweigh the benefits. Under International Humanitarian Law, dams are considered “installations containing dangerous forces.” 

 “Hydro-geologists and engineering experts consider all crucial factors in the siting and designing of the dams. These factors include but are not limited to good topographical location along the river path, right geological structure and availability of sufficient water,” says Balebetse adding that the two rivers may not have all those features. “In both these rivers, there are no adequate depressions or valley along their paths for the location of the dams. Indeed, if there was a river passing through Serorome Valley, it would be one site to consider because of its good topographical location.” 

According to him, for the right geological structure, existence of hills surrounding the river basins would not only provide protection from accidental dam breakage or failure, but would also create good depth of the dams. With regard to the latter, he gives the examples of Ntimbale and Nnywane dams. 

 “Our country is a very flat with virtually no dam sitings available to build the dams, save for small dams for agricultural use. Our rivers mostly flow from the western to eastern part of the country and all converge on Molopo River in South Africa,” he says. 

The eastern part of the country (which is densely populated and has high demand for water) has fewer depressions and hills, and with the construction of dams like Letsibogo, Dikgathong, Thune and Lotsane (that have rock structure that cannot allow the seepage of water), sites for proper locations of dams have been exhausted and the government has not been able to locate any more sites.  

In the particular case of Segoditshane River, Balebetse notes that it passes through Gaborone and that a dam failure would have disastrous consequences. 
“We must be very careful that our need to have security of water supply by constructing dams is counterbalanced by engineering, economic and environmental considerations. Otherwise, there can be significant repercussions. There have been serious dam failures around world, even in First World countries like the United States. The Far East has also experienced dam failures due to unpredictable structural dam failures arising from poor location of dams, poor quality construction materials, inadequate maintenance and other associated factors,” Balebetse says.
 
How then should water from these rivers be harnessed if dams are not an option? Even the minister seems to be at his wits’ end because without giving concrete answers, he told parliament that the government should not stop looking for ways to harvest water as it passes. 
 
“I think that is where the challenge is and that is what we should invest in, because these flash floods which happen once in a blue moon you want to be able to capture that water one way or the other to ensure that we can put it to better use,” Mokaila said.
 

RELATED STORIES

Read this week's paper