Determination of water required to recover from hydrological drought: Perspective from drought propagation and non-standardized indices

When a severe drought occurs, people often question the amount of water required to recover from the drought which is difficult to determine. Here, we present a method to determine the amount of water required, including both runoff and precipitation, for hydrological drought recovery from a drought propagation perspective. We also consider multi-scale meteorological and hydrological anomaly indices (MAI and HAI) with non-standardized properties. We present three rainfall-driven basins in southern China to validate the proposed approach using long-term monthly runoff and precipitation records. Drought propagation characteristics (such as duration, severity, development, and recovery processes) were extracted using the HAI and MAI obtained via a threshold level method and run theory. The proposed method allows estimating the amount of water required, including runoff and the corresponding precipitation, for any hydrological drought to recover to normal using HAI and MAI. Moreover, a linear relationship between runoff and the corresponding precipitation was established (R-2 > 0.99) to estimate the amount of precipitation required to recover from a certain hydrological drought. The methods presented in this study can be used for assessing and managing water resources and ecosystem response during periods of hydrological drought.