Lags in hydrologic recovery following an extreme drought: Assessing the roles of climate and catchment characteristics

Abstract

Drought, generally characterized by below-average water supply, propagates through thehydrologic system with consequent ecological and societal impacts. Compared with other drought aspects,the recovery of drought especially in the hydrological components, which directly relates to the recovery ofwater resources for agricultural, ecological and human needs, is less-understood. Here, taking the Millen-nium drought in southeast Australia ( 1997–2009) as an illustrating case, we comprehensively examinedmultiple aspects of the meteorological (i.e., precipitation) and hydrological (i.e., streamflow and base flow)droughts across 130 unimpaired catchments using long-term hydro-meteorological observations. Resultsshow that the duration and intensity of the meteorological drought are both lengthened and amplified inthe hydrological drought, suggesting a nonstationarity in the rainfall-runoff relationship during a prolongeddrought. Additionally, we find a time lag commonly exists between the end of the meteorological droughtsand the end of the hydrological drought, with the recovery of base flow showing a longer lag than therecovery of streamflow. The recovery rate of precipitation after drought was found to be the dominant fac-tor that controls the recovery of hydrological droughts while catchment landscape (i.e., valley bottom flat-ness) plays an important but secondary role in controlling the lags in the hydrological recovery. Otherhydro-climatic factors and catchment properties appear to have only minor influences governing hydrologi-cal drought recovery. Our findings highlight a delayed response in the terrestrial components of the hydro-logical cycle to precipitation after prolonged drought, and provide valuable scientific guidance to waterresources management and water security assessment in regions facing future droughts Show more