New diagnostic framework makes integrated water storage a reality

In 2010, water levels at Lake Kariba were so high that the Kariba Dam had to be opened to prevent flooding. By January 2023, capacity at the world’s largest artificial lake, which straddles the Zimbabwe–Zambia border, had plunged to just 2 percent. Water levels have risen slightly since then, but the lake’s wild fluctuations in volume have sparked serious concern for water and energy security in both countries.

As climate change brings increasingly erratic rainfall, the problem of unreliable water supplies will continue to grow more acute – not just in Zimbabwe and Zambia, but across much of the globe. “In simple terms, we’re facing a problem of insufficient water,” explains Dr Jonathan Lautze, Research Group Leader at the International Water Management Institute (IWMI). “But supply isn’t constantly insufficient – there are shortfalls some years or seasons, but there are also periods when there’s enough water. Managing these variations is a major challenge in a lot of the Global South – and a lot of the Global North, frankly.”

Water storage diagnostic

As part of his role as NEXUS Gains Work Package 2 Lead, Dr Lautze is leading the development of a water storage diagnostic to address this challenge. This diagnostic framework will allow water planners and basin managers to diversify their water storage options by providing the tools to assess a much broader range of stores – including dams, aquifers, and soil moisture – in an integrated way.

The need for diversified water storage planning and management has been widely recognized in recent years. However, the complexity of accurately assessing less conventional storage types, such as soil moisture, has slowed the practical application of theory. “In terms of getting your hands dirty – understanding the different storage types and volumes in a particular geography – there hasn’t been much to date,” comments Dr Lautze. “That’s why I’m proud that we’re taking a practical approach with the water storage diagnostic.”

To make integrated water storage planning and management a reality, Dr Lautze and his colleagues are bringing together and developing a broad selection of powerful assessments into the diagnostic framework. These include recession flow analysis and hydrogeological modeling for aquifers, analysis of earth observation data for dams, and the use of in-situ, remotely sensed, and modeled data for soil moisture.

Comprehensive basin plans

By identifying and comparing the opportunities and risks of various water stores in a coherent manner, the water storage diagnostic will help planners and managers smooth out the variations in water supply and minimize periodic shortfalls. Dams will continue to play an essential role in water storage, but they should no longer be expected to bear the burden alone. “It’s not about abandoning any form of water storage,” clarifies Dr Lautze, “but about achieving a more balanced approach. We’re going to keep focusing on dams, but we will be able to think more proactively about using dams in conjunction with other storage types.”

Dr Lautze and his team hope to see the benefits of the diagnostic framework reflected in the development of new basin plans, which have historically relied heavily on gray infrastructure like dams to meet regional water needs. “My ambition is that we can work with decision-makers to come up with more comprehensive basin plans that sufficiently consider all storage types and substantively integrate them,” he says.

Plugging into water planning in Zimbabwe

The first chance to put the water storage diagnostic to use is anticipated in 2024, when NEXUS Gains is expected to contribute evidence on storage options to planning meetings of the Gwanda District Rural Development Council’s Water, Sanitation and Hygiene subcommittee, in Zimbabwe. The growing concerns over the beleaguered Kariba Dam represent both the escalating effects of climate change in Zimbabwe and the increasing risk of undiversified water storage solutions. Emerging results will allow Dr Lautze’s team to showcase the potential of different storage types and, it is hoped, improve the reliability and sustainability of the country’s water storage planning and management.

The ultimate aim is to introduce the water storage diagnostic to water planners and basin managers in river basin organizations and catchments councils across Southern and Eastern Africa and Central and South Asia. Specific regions include Southern Africa’s Limpopo Basin, the Aral Sea of Central Asia, and the Ganges Basin in South Asia. Reflecting on this ambitious goal, Dr Lautze is cautiously optimistic about the potential of the diagnostic framework. “It takes sustained interaction and sustained effort to shift attitudes and institutional norms toward more diversified and greener water storage. But the new water storage diagnostic represents an exciting development.”

For more information, contact Jonathan Lautze, Research Group Leader at IWMI: j.lautze@cgiar.org

The development of the water storage diagnostic has been supported by funding contributions to the CGIAR Trust Fund. Additional bilateral investment has been provided by the United States Department of State project, “Built Water Storage in South Asia.”

Header image: Micro-hydropower system in Zimbabwe. Photo by David Brazier/IWMI.