Abstract:

[Objective] In 2023, influenced by abnormal atmospheric circulation and sea temperature anomalies, the Dianchi Lake Basin, situated in the central Yunnan-Guizhou Plateau, suffered a severe drought. The basin did not enter the rainy season until late June. The annual average temperature, highest daily average temperature, total number of meteorological drought days, and number of extreme drought days all broke historical records, leading to a substantial reduction in river inflow and limited water replenishment of lakes and reservoirs. This study aims to enhance the ability to respond to high-frequency drought events and to guide drought relief efforts under the compounded effects of drought. [Methods] Based on long-term hydrological data series in the basin, this study analyzed the precipitation and runoff conditions in 2023 using GIS-based spatial interpolation and mathematical statistical methods. The drought condition in 2023 was diagnosed using the Standardized Precipitation Index (SPI) and low-flow return periods. [Results] In 2023, the Dianchi Lake Basin experienced a drought event with extensive spatial coverage and long duration, manifesting as a basin-wide moderate-level drought. Nine months of the year had basin-wide droughts of varying degrees, and one month had localized drought. Among them, months with severe drought or above accounted for half of the year. River runoff showed phenomena of low flow during the flood season and an early onset of low flow. From April to July and September to December, control cross-sections experienced low flows with return periods of 100 years or more, causing severe shortages in regional water storage projects and urban-rural water supply and use, thereby profoundly impacting the sustainable utilization of water resources. The analysis indicated that precipitation and water resources in the basin may exhibit a continuous decreasing trend. This drought event was a typical case of the combined effects of “circulation anomalies, underlying surface feedback, and water resource vulnerability.” [Conclusion] This study recommends suggestions integrating intelligent early warning,engineering resilience,and institutional innovation:1) improving the drought prediction, forecasting, and early warning system; 2) accelerating the construction of the Central Yunnan Water Diversion Project and small-scale water source projects; 3) strengthening water resource management and scientific scheduling; 4) advancing research on the utilization of rainwater and floodwater resources; 5) exploring the dynamic control of Dianchi Lake’s water level. The findings not only provide a Chinese solution for drought relief in global karst plateau regions but also offer scientific support for in-depth exploration of the occurrence and development patterns of regional droughts, promotion of ecological protection and restoration, enhancement of drought monitoring and early warning systems, and improvement of response capabilities. This holds significant practical importance for ensuring urban and rural water supply security in the context of frequent droughts.

Key words: drought diagnosis, long-series hydrology data, Standardized Precipitation Index(SPI), drought intensity, low-flow return period, Dianchi Lake Basin, drought relief and disaster reduction