Tanzania’s big decision: The mega-dam and its negative impacts, or an energy alternative?

Wednesday September 26 2018
pic energy

Elephants at the Selous Game Reserve, a designated World Heritage Site. PHOTO|FILE

Preparation has started in Tanzania on the Stiegler’s Gorge Dam. If built, this project will be the joint second-largest dam in Africa. However, the project is in the Selous Game Reserve, a protected area the size of Switzerland that is a designated World Heritage Site because of its ecological importance. Nethertheless, President Magufuli has made the dam a flagship for his government.

I have spent the past four years researching the history and resurrection of the Stiegler’s Gorge Dam project, which dates back to the start of the 20th Century when German engineer Stiegler was killed by an elephant whilst surveying the dam site.

But rather than a British white guy in Oxford lecturing Tanzanians about what is in their best interests, I want to stress the trade-offs that should be recognised by the government in choosing to build the dam. That if the Stiegler’s Gorge Dam is built Tanzania could have large amounts of electricity, but the dam will also have undeniable, significant negative impacts on some citizens and on globally outstanding environments. You can’t “have your cake and eat it”.

The key impacts of this dam aren’t in where or how much its’ reservoir will cover. The main effects are from the dam blocking the flow of water and sediment.

The untamed Rufiji River has three key functions.

The first is in the core area of the Selous World Heritage Site, which is just below the proposed dam. This consists of marshland, lakes and shifting riverbeds, which are maintained by water and fertile soil from the river’s annual flood.


In the land below the reserve, a large floodplain provides rich agricultural opportunities that are utilised by the Warufiji people. Their farming is also underpinned by the fertile sediments and water from the Rufiji River’s annual flood, which also sustains fishing lakes.

At the delta, where the Rufiji River meets the sea, the annual flood again plays a key role. Its release of fertile soil physically creates a delta and sustains its chemical balance. This delta is also environmentally rich, home to the largest mangrove stand in East Africa and is meant to be protected by a global treaty called Ramsar. The delta also hosts Tanzania’s economically-richest fishery. Again the Rufiji River’s annual flood is key: It produces a boom in marine life, most importantly in prawns, and brings migratory Whale Sharks.

However, the dam will block sediment and water. Therefore, it will fundamentally change these three important downstream economies and ecologies, endangering the core area of the Selous Reserve, the livelihoods of the Warufiji and the environmentally-rich delta.

Nethertheless, the dam will produce significant amounts of hydroelectric power. In fact if it was built tomorrow, it would be the joint largest hydropower project in Africa. Such electricity is important for Tanzania’s planned industrialisation and efforts to reduce poverty.

But is this dam going to meet Tanzania’s needs and electricity aspirations?

Hydropower in Tanzania has a poor record. The country’s regular, months-long electricity blackouts are caused by drought years that leave reservoirs with less water. Building such a large hydropower project therefore carries risks of making Tanzania more weather dependent at a time when climate change is likely to make rainfall increasingly variable.

It is also important to ask what Tanzania wants to use the electricity for. Electrification, meaning the spreading of access to electricity, can be more expensive, less reliable and slower when pursued through large centralised schemes like the Stiegler’s Gorge Dam. It will likely take over 10 years to build. In contrast small hydropower plants (called micro-hydro), wind and solar power offer Tanzania a tangible opportunity to deliver mass electrification at a faster, cheaper and more reliable rate, at least compared to the record of electricity projects to date.

Finally, given the project will cost upwards of $3.6billion, it is crucial to ask if this dam is worth it: Will it really address Tanzania’s development needs? The Stiegler’s Gorge is planned to produce 2,100MW, over double what the country currently uses. Models independent of the government predict that with plans for electrification and industrialisation, Tanzania will need ~2000MW by 2020, which the country is already due to exceed with gas projects at Kinyerezi. Will Stiegler’s Gorge therefore become a white elephant, a large electricity project without an economic use?

The idea of excess power being sold to Tanzania’s neighbours seems unlikely given Rwanda, Uganda, Kenya and Zambia’s ambitious power plans, and given Ethiopia’s head-start in agreeing electricity trades. There appears to be a real risk of Stiegler’s Gorge becoming an expensive, semi-used infrastructure project costing the Tanzanian taxpayer US$3.6 billion.

The Tanzanian government therefore faces a series of questions about the economic effectiveness and socio-environmental sustainability of the Stiegler’s Gorge Dam. Is it the solution to Tanzania’s development issues? Is it going to deliver the electricity that Tanzania needs? Are the trade offs to Tanzanian citizens and globally important environments worth the electricity?

If centralised electricity generation for the national grid is wanted, there are alternatives: Hydropower projects have been designed upstream of the Stiegler’s Dam that would have less socio-environmental impacts (e.g. Mnyera, 668MW; Rumukali Dam, 222MW; Ruhudji, 358MW). Tanzania has also identified large solar and wind potentials which are only starting to be developed. Geothermal is another possibility with neighbouring Kenya building thousands of megawatts in the rift valley that is shared with Tanzania. There are also further potentials for burning indigenous gas and coal, although this would increase global warming.

This article does not provide answers. Development is a messy path full of winners and losers, as Europe and America show. Rather I have posed a set of questions that I hope will provoke better understanding of the gravity of Tanzania’s choice in building Stiegler’s Gorge Dam.

Barnaby Dye is a research associate at the FutureDAMS project at the University of Manchester. He is also completing a doctorate at the University of Oxford which has looked at dam building and the energy sectors of Rwanda and Tanzania.