Watersheds may not recover from drought

Abstract

Staying dry Is precipitation all that a watershed needs to recover from drought? Conventional wisdom says yes, but this is not necessarily true. Peterson et al. studied streamflow and precipitation in 161 watersheds in southeastern Australia across the Millennium Drought, which stuck the region during the first decade of the 21st century (see the Perspective by Tauro). They found that runoff in approximately one-third of the watersheds had not returned to predrought levels even after 7 years despite the resumption of more normal precipitation. The authors suggest that these longterm changes are due to water loss from increased transpiration. Watersheds may thus have multiple states and a finite resilience to transient disturbances, and hydrological droughts can persist long after meteorological droughts. Science , this issue p. 745 ; see also p. 680