Spatiotemporal Characteristics and Driving Factors of Drought in the Pearl River Basin Based on Temperature Vegetation Dryness Index

Abstract

Using the temperature vegetation dryness index (TVDI), Sen’s slope estimation, and the Mann-Kendall test, this study analyzed the spatiotemporal characteristics and trends of drought in the Pearl River Basin from 2001 to 2023, and examined the influences of temperature and precipitation on TVDI. The results indicated that the average TVDI over the study period was 0.6607, with a standard deviation of 0.0186, reflecting a general state of moderate drought and a significant downward trend in drought severity. On average, the proportions of areas with no drought, light drought, moderate drought, severe drought, and extreme drought were 1.09%, 11.36%, 78.85%, 8.33%, and 0.37%, respectively. Over the past 23 years, drought severity has generally increased from north to south. Extreme drought was concentrated in the southern Leizhou Peninsula (Guangdong), while severe drought mainly occurred in the Leizhou Peninsula, the Pearl River Estuary, and parts of eastern Guangdong (Jieyang, Chaozhou, Huizhou), as well as Nanning, Baise, and Qinzhou in Guangxi province. Gejiu City in Yunnan also experienced frequently severe droughts. In contrast, lower TVDI values were primarily found in southeastern Guizhou, northeastern Guangxi, and northwestern Guangdong. Drought severity in the eastern Pearl River Basin exhibited a worsening trend, whereas conditions in the west tended to improve. Approximately 70% of the basin showed a gradual decline in drought intensity. At a 0.05 significance level, significant drying was noteworthy in the Pearl River Delta, eastern Leizhou Peninsula, northern Guangdong, Jieyang (Chaozhou), and eastern Yunnan. In contrast, significant drought alleviation occurred in Qinzhou, Fangchenggang, and Baise (Guangxi), the border region of Yunnan–Guangxi–Guizhou, as well as Yangjiang, Maoming, eastern Meizhou, Shanwei, and Huizhou in Guangdong province. Regionally, TVDI was significantly and negatively correlated with air temperature, suggesting that rising temperatures contributed to drought alleviation. Overall, both temperature and precipitation showed negative effects on drought severity. TVDI was negatively correlated with precipitation across all land use types, and the strongest correlation was identified in grasslands. Except for forest land, TVDI in other land use types exhibited weak correlations with air temperature.