Tono irrigation scheme, Ghana.

Ghana’s Tono scheme (pictured) provides water to only about 60% of its original target area, but is still more successful than most large-scale irrigation projects in sub-Saharan Africa. Credit: Timothy Foster, Sarah Redicker and Roshan Adikhari

Sustainability

Massive water projects leave a parched landscape high and dry

Ambitious irrigation schemes are planned for sub-Saharan Africa — but those already built have a dismal track record.

Most large-scale irrigation projects built in sub-Saharan Africa over the past six decades have failed to work as advertised.

Local governments and international agencies are once again investing in massive irrigation projects, such as dams and canals, in sub-Saharan Africa. To inform such efforts, Thomas Higginbottom and his colleagues at the University of Manchester, UK, compiled data from 79 irrigation schemes built in the region since the 1940s. The researchers then used satellite data to assess the land area irrigated by each project.

The researchers found that irrigation schemes overwhelmingly fell short of their billing: the median irrigated land area across all projects was just 16% of their proposed goals. A scheme’s failure risk was not linked to either its size or local climate-change fluctuations, although projects in countries with more stable governance were less likely to fail. The data show no improvement in success rates over the 60-year period.

Because massive irrigation schemes are hugely expensive and have significant impacts on local communities, the authors advise that more research is needed to make these projects cost-effective and sustainable.