Impacts of Different Socioeconomic Development Levels on Extremely Wet/Dry Events in Mainland China

The impacts of human activity (denoted by population), economic, and social development (denoted by gross domestic product–GDP) on extremely wet/dry (or drought) events are important for humans to tackle extreme hazards. This research aims to investigate the variations in maximum values (SPEI_MAX) and minimum values (SPEI_MIN) of a 12 month standardized precipitation evapotranspiration index (SPEI12-month) for the selected 525 sites at different socioeconomic development levels (SDLs) (classified by population and GDP) in China between 2000–2018, and to analyze the impacts of increased population/GDP/SDLs on extremely wet/dry events. The linear correlations between SPEI12-month/SPEI_MAX/SPEI_MIN and population/GDP were conducted for all the sites. The relationship between linear slopes of population (PopuLS)/GDP(GDPLS) and SPEI_MAX (SPEI_MAXLS)/SPEI_MIN (SPEI_MINLS) were further studied. The results show that the extremely wet events denoted by SPEI_MAX become worse and the extreme drought events denoted by SPEI_MIN tend to be milder over time. The years 2016 and 2011 were extremely wet and extremely dry in China. There were general increasing trends in SPEI_MAX and decreasing trends in SPEI_MIN as the SDL increased from 1 to 6. This gradual, continuous increase/decrease potentially affected levels 5 and 6. Moreover, extremely wet events were more severe in developed big municipal cities of higher SDLs and extreme drought events were more severe for lower SDLs. This research can supply references for policy makers to prevent extreme disasters.