Spatio-Temporal Change of Drought and Flood in northern Henan Province During 1961-2015 Based on Standardized Precipitation Evapotranspiration Index

The spatial-temporal evolution of drought and flood events and their occurrence frequency in northern Henan Province, China are quantitatively analyzed during 1961 similar to 2015, based on temperature and precipitation data, by using Standardized Precipitation Evapotranspiration Index (SPEI) and indicators of drought and flood. The results show that there are significant differences in the periodicity and fluctuation of SPEI value at different time scales in the north of Henan Province during the study period. Firstly, at monthly scale, the monthly frequency of drought in the northern part of Henan Province shows a decreasing trend, but that of flood shows an increasing trend. Secondly, at seasonal scale, Autumn droughts have the highest occurrence frequency, followed by Summer droughts and Winter droughts. But for flood events, Summer floods have the highest frequency. Finally, as to the inter-annual variability of droughts and floods, serious droughts are occurred in northern Henan Province in the 1980s, 2000s and 2011-2015, but serious floods occur in the 1960s and 1970s.