Almost one-third of the water used in the western United States goes to crops that feed cattle.

Eating beef isn’t just bad for the climate. The irrigation of alfalfa, hay, maize (corn), sorghum and other crops eaten by cattle is the largest consumer of water in the United States — and the leading cause of abnormally low river flows.

In many areas of the United States and around the world, freshwater use is approaching or exceeds the rate of natural replenishment, and is depleting rivers and hurting fisheries. Brian Richter at the non-profit organization Sustainable Waters in Crozet, Virginia, and his colleagues identified areas across the United States where crops are grown to feed cattle. The team then modelled the impact of these crops on rivers.

The results suggest that, on average, cattle-feed crops account for 32% of water use in the western United States, and that cattle-feed irrigation is the leading driver of water depletion in one-third of all western rivers.

Allowing land where cattle-feed crops are grown to lie fallow for limited periods would greatly relieve water scarcity in some rivers, the authors found.