Agricultural drought recovery characteristics and water requirement for rapid drought recovery in the Huai River Basin, China

Huai River Basin. The study aims to analyze the spatiotemporal changes in the occurrence and recovery of agricultural droughts of different degrees in the Huai River Basin through the Standardized Soil Moisture Index (SSMI) and the Weighted Average Precipitation Index (WAPI). It also determines the cumulative precipitation amounts leading to the rapid recovery of agricultural droughts with 1–2 days of additional rainfall. This method is designed to accurately identify the characteristics of drought recovery and the actual effective weighted precipitation required for rapid recovery on a daily scale. The findings indicate that mild and extreme droughts frequently occur in the Huai River Basin. The longer the drought persists, the longer the recovery time. Recovery times in the southern part are the shortest. In the past 33 years, there have been 22 events of rapid recovery from agricultural drought within one day following a period with sufficient cumulative rainfall. On average, each event requires a Weighted Average Precipitation Index (WAPI) of 660 mm based on cumulative rainfall from an earlier time period to facilitate drought recovery within one day of additional rainfall. To rapidly recover from severe drought and more severe drought conditions within two days of heavy rainfall, the corresponding WAPI based on sufficient cumulative rainfall from an earlier time period reach nearly 1000 mm. • The daily precipitation values were replaced with the WAPI. • The characteristics of drought recovery were explored. • Cumulative water volumes required for rapid drought recovery were determined.