Climate change and water security in Africa: preparing for the impacts

If we look at the historical record for a number of river basin systems in Africa – the Zambezi and Nile for instance – we see they already have experienced substantial levels of variability.

Comparing the periods 1931-1960 with 1961-1990 for each river basin, for instance, shows how both systems experienced large declines in river flow and precipitation between the two periods.

Re-thinking assumptions

Such high levels of variability are often not appreciated sufficiently.

For example, in the past we've assumed that hydrological systems in Africa are relatively static over time, and the design, construction, and operation of hydroelectric dams is often based on the idea of stationarity; that water availability doesn't fluctuate over the long-term.

This assumption has had some damaging consequences, particularly in relation to hydroelectric power generation (HEP) which is the major source of electricity for many countries in sub-Saharan African.

For example, in the case of Kenya a 25% reduction in hydropower associated with drought in 2000 resulted in an estimated 1.5% reduction in GDP.

It's important to address the cause and identify measures to deal with such events so we plan effectively for future climate change impacts.

Furthermore, the assumption of stationarity is undermined by climate change.

Interacting physical and social systems

It's a truism that hydrological systems comprise both physical systems and social systems that interact, but sometimes our research and management approaches do not fully reflect this.

Many river basins in Africa are international, creating a need to address cross-border water allocation and consider how this could be affected by climate change. For example, how to share deficits during periods of drought.

Development objectives in many African river basins involve new large-scale dams and HEP and expansion of irrigation while at the same time needing to maintain river flows to support critical environmental functions.

Rapid development is enhancing such interactions and interdependencies, driving the need to consider options and their outcomes in a rigorous manner, including how new developments might perform under climate change conditions.

Methods for evaluating trade-offs between three areas of water use

The current phase of our research in UMFULA is developing tools to evaluate possible trade-offs or co-benefits in three different domains of water use: HEP, irrigation, and environmental services.

By simulating many combinations of management options and infrastructure [and their performance under future climate change conditions], we hope to identify pathways that allow sustainable development, without compromising different stakeholder priorities.

For example, by making adjustments to reservoir outflows, it may be possible to recreate a more natural river flow regime that maintains environmental and livelihood needs downstream, with only minor impacts on electricity generation.

Water security also includes protection from short-term water-related hazards

Including short-term risks as a part of measures to promote water security is also important, since climate change will affect the frequency and severity of extreme events such as droughts and floods alongside changing future average conditions.

As much of Africa is rapidly urbanising preparation for climate change needs to include a focus on cities where impacts and disruption from floods are increasingly felt.

Through research on the 2015/16 El Niño event we found businesses in the capital cities of Zambia, Botswana and Kenya experienced major disruption to their activities due to El Niño-related hydroelectricity outages, water supply disruption and flooding, respectively.

Improved preparation for and management of short- and long-term threats to water security requires establishing effective and equitable processes for dealing with current variability and extremes: this is a pre-condition for achieving water security in the face of climate change.

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