On threshold of drought and flood disasters in Huaihe River basin

Based on the daily precipitation from 110 stations in the Huaihe River Basin during 1959—2008, the crop damage area due to drought and flood disasters from 1978 to 2008, the hazard factor from precipitation, the extent of damage for crops, and the spatial-temporal characteristics of disasters are analyzed. The thresholds of drought and flood disasters are calculated and the relationships between the thresholds of drought and flood disasters and the crop damage area are established. The result shows that first, the thresholds of drought and flood disasters can be calculated using the ratio of the cumulative event precipitation to the mean cumulative precipitation of 1959—2008. The ratio can well reflect the severity of flood and drought disasters of varying degrees, and can meet the requirements for analyzing flood and drought events in the study area. Second, the drought and flood disasters quantified by the calculated thresholds can reflect all degrees of drought and flood disasters and the affected areas. The thresholds and the affected areas have similar variation tendency. In particular, the threshold of drought disaster and the crop damage area are highly correlated as revealed by the high value of correlation coefficient (0.96). Thus, a model for forecasting the crop damage area is developed based on the threshold of drought disaster.