Quantitation of meteorological, hydrological and agricultural drought under climate change in the East River basin of south China

Documenting the joint probability of meteorological-hydrological, meteorological-agricultural, and hydrological-agricultural drought can be invaluable for understanding drought evolution under climate change in a high-diversity watershed of south China. Through constructing the edge and joint distribution functions of multi drought indices (SPEI, SPI, SSI, and SWI) based on SWAT and copula methods, we explored the evolution of multi droughts under climate change in the East River basin. During 1997–2017 and 2023–2099, we used logistic, generalized pareto, and normal distributions to construct edge distribution functions of SPEI, SPI, SWI, and SSI. For the four indices, the probability of slight drought increased with rcp2.6, 4.5, 6.0, and 8.5, and it was higher than moderate drought. Also, Clayton, Frank, Gumbel, and Gaussian copula functions were used to construct joint distribution functions of SPEI and SSI, SPEI and SWI, SSI and SWI to quantify their interactions. During 1997–2017, the probability of slight drought was 26.15 to 41.06 %, and the return period changed from 3.8 to 2.4 years. The joint probability of meteorological-hydrological, meteorological-agricultural, and hydrological-agricultural drought in slightly was 24.4 to 31.32 %, 14.95 to 22.63 %, and 6.18 to 22.05 %, respectively. During 2023–2099, the joint probability of droughts in moderately was 3.76 to 14.19 %, and the return period was 7 to 26.6 years. Our results provide a quantitative assessment of single and joint probability of meteorological, hydrological and agricultural drought, which could be used to support watershed water resource management.