The late 1950s saw the first of four large hydropower dams constructed along the main stem and major tributaries of southern Africa’s greatest river, the Zambezi. A singular focus on power generation led to unforeseen and unintended consequences on the region’s ecology and its human communities. 

The dams displaced tens of thousands of people upstream and disrupted the traditional livelihoods of many more living downstream. A river stilled by dams no longer deposits nutrients on floodplain fields, nor does it create the seasonal wetlands that once enhanced habitat for native fish and wildlife, including crocodiles and elephants.

The Conservancy’s Patrick McCarthy works with hydropower specialists in the Zambezi basin who now increasingly recognize that managing for natural river flows can produce energy while protecting — even restoring — ecosystems and rural livelihoods. McCarthy recently spoke with nature.org about this growing partnership to enhance Zambezi River management for nature and people.

nature.org: What are the ecological reasons to address dam management on the Zambezi River?

McCarthy: The answer goes to the paradox of this great river. The Zambezi is one of the biggest and wildest rivers in all of Africa. Its wildlife is as abundant and vibrant as better known habitats in Kenya and Tanzania.

But the problem is that four major dams have profoundly changed the way the river behaves. Ecological connections have been severed, and aquatic habitats and lands along the river have been degraded. A whole host of creatures evolved with the natural dynamics of this river over thousands of years, and now the primary driver of their life cycles is lost.

nature.org: Can you speak to some of the recent effects on people from floods that hit the Zambezi?

McCarthy: Over the past few years — perhaps due to climate change — rainy season storms have become more severe and the resulting floods less predictable.

Early in 2008, for example, the operators of Kariba Dam, which spans the river between Zambia and Zimbabwe, were forced to release water suddenly to prevent floodwaters from overtopping the dam. In spite of great efforts by the dam operators, many people downstream were taken by surprise. They lost houses and crops, and some lost their lives. They were caught unaware when the released water combined with floods from local tributaries. Lack of information, planning and a good communications system tied the hands of the dam managers and villagers as they struggled to deal with these unexpected floods. 
 

nature.org: How can our partnership make a difference?

McCarthy: Our partnership can help with new communication, coordination, equipment, dam operating rules — when to open and close the flood gates — and also with data gathering and sharing networks across three countries. Mostly, we need to prescribe environmental flows: low and high flow pulses that mimic the river’s natural cycles and provide a range of benefits for nature and people.

We need to allow these rivers to provide again the ecosystem services that people have depended on for thousands of years: fisheries, agriculture and clean drinking water. 

 
nature.org: Last year the Conservancy hosted a tour of Savannah River hydropower sites for dam managers from southern Africa. What progress have we made since that tour?
 
McCarthy: We asked the dam managers where they most needed our technical support, and they outlined three top priorities:

• Figure out environmental flows to help habitats recover
• Manage the dams as a network rather than individually
• Collect and exchange data in a timely way 

The agencies have since drafted a work plan, and we’ve responded with an options report that outlines precisely how we and our partners can help them complete their plan and fulfill their long-term goals.

 
nature.org: Tell us about your recent trip to Africa.
 
McCarthy: First I went to Lusaka, Zambia, to meet with local and international non-profits. We discussed potential collaborations on nature conservation and community development in the Zambezi basin.

Then I met with our partners at the annual Zambezi Basinwide Stakeholders Forum in Lilongwe, Malawi. The Zambezi’s foremost dam- and water-management agencies were all there, along with representatives from WWF from Zambia and Mozambique and from the U.S. Army Corps of Engineers. It was an ideal opportunity to plan exactly what we’re going to do in 2009.

We came away from the forum with a strengthened partnership and a joint action plan. We’re moving toward true science-based, community-supported flows for the Zambezi River. Our next step is to organize a series of workshops that will establish exactly what environmental flows look like — how much water will be sent downstream, and when, for the greatest benefit to river ecosystems and people.

 

Nature picture credits (top to bottom, left to right): Photo © Brian Richter/TNC (Children along the Zambezi River); Photo © Laura McCarthy (Patrick McCarthy); Photo © Patrick McCarthy/TNC (Tailwaters of the Cahora Bassa Dam on the Zambezi River).