Plenty of Water, but Crops Are Going Thirsty

Irrigation can help farmers double or triple their crop yields, but the vast majority of Sub-Saharan African farmers rely on rainfall alone. Just 3.5 percent of the region’s farmland is equipped for irrigation, compared with 37 percent in Asia and 18 percent worldwide.

Is it because Africa just doesn’t have the water available for irrigation? Hardly. An IFPRI discussion paper by Liangzhi You and colleagues presents results of a study on the potential for irrigation in Africa. It points out that Sub-Saharan Africa has more renewable water per person than the global average—7,455 cubic meters a year, compared with 6,859 cubic meters a year worldwide—but the region uses only 1 percent of that water for irrigation.

The problem is that Sub-Saharan Africa lacks the irrigation infrastructure to take advantage of its water resources. It would not make economic sense, however, to start blanketing the continent with massive dams. Irrigation is expensive, so the economic viability of an irrigation project depends on keeping costs down.

IFPRI’s study is unique in looking at both the biophysical and the economic potential for irrigation. “It has to be economic for farmers,” says You. He notes that in parts of Africa, farmers lack access to markets for selling their goods, and this situation affects what kind of irrigation systems will be economically viable.

The study finds that in most places, small-scale irrigation will give higher returns than large dams because smaller systems cost less to build. Nigeria has especially good potential for both large- and small-scale irrigation schemes that will pay off handsomely.

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