Over the last forty years, demand for food in developing countries has increased more than threefold. In response, these countries have increased their production of irrigated crops from two to fourfold. As a result, average yield has more than doubled for rice and maize, trebled for wheat, and quadrupled for fruits and vegetables. Water productivity has increased sharply during the same time.
However, these gains have been neither universally successful nor universal in scope. Governments led the expansion of large-scale irrigation, and the results have been mixed, with many supply-led and bureaucratic programs producing disappointing results. In many basins, water productivity remains startlingly low, and adoption of modern technology is slow.