24 Jul 2017 --- Water use for food production today largely occurs on the expense of ecosystems. About 40 percent of the water used for irrigation are unsustainable withdrawals that violate so-called environmental flows of rivers, a new study shows for the first time. If these volumes were to be re-allocated to the ecosystems, crop yields would drop by at least 10% on half of all irrigated land, especially in Central and South Asia.